JP3632092B2

JP3632092B2 - Screen printing machine

Info

Publication number: JP3632092B2
Application number: JP06111194A
Authority: JP
Inventors: 中村　　秀男; 春夫三階; 浩志岡田
Original assignee: 株式会社日立インダストリイズ
Priority date: 1994-03-30
Filing date: 1994-03-30
Publication date: 2005-03-23
Anticipated expiration: 2020-03-23
Also published as: JPH07266537A

Description

【０００１】
【産業上の利用分野】
本発明は、スクリーンマスクの一面側にプリント配線板を配設し、そのスクリーンマスクの他面側でスキ−ジを移動させることにより、はんだペ−ストを前記スクリーンマスクの他面に押し付けて、そのはんだペーストを前記スクリーンマスクに設けられた開口部を通して前記プリント配線板上に前記開口部の形に印刷するスクリーン印刷機に係り、特に微細なピッチに配列されている開口部においてもかすれやにじみが生じること無くはんだペーストを印刷することができるスクリーン印刷機に関するものである。
【０００２】
【従来の技術】
プリント配線板に半導体装置、抵抗、コンデンサ等の電子部品を搭載（固着）して所要の電子回路を実現するために、スクリーン印刷機を用いてプリント配線板にはんだペ−ストを印刷することが行われている。
この種の従来のスクリーン印刷機を図１６乃至図２１に基づいて説明する。
図１６乃至図２１において、１はプリント配線板である。このプリント配線板１は、上面に後述するはんだペースト９が印刷される複数個の配線パッド２を備える。
この配線パッド２は、後述する電子部品１３のリード端子１４と後述するはんだペースト９を介して接続されるものであり、実装する電子部品１３のリード端子１４に倣って配設されている。例えば、図１６及び図１７中において、右側Ｒに実装される電子部品１３Ｒのリード端子１４Ｒの数は比較的少なく、かつそのリード端子１４Ｒ間のピッチは比較的粗いので、その右側Ｒにおける配線パッド２の数は比較的少なく、かつその配線パッド２間のピッチは比較的粗い。一方、左側Ｌに実装される電子部品１３Ｌのリード端子１４Ｌ等の数は比較的多く、かつそのリード端子１４Ｌ間のピッチは比較的微細であるので、その左側Ｌにおける配線パッド２の数は比較的多く、かつその配線パッド２間のピッチは比較的微細である。
【０００３】
３はプリント配線板１の上面に一面（図１７中下面）が対向するように配設した例えば金属（メタル）製のスクリーンマスクである。このメタルマスク３には複数個の開口部５及び７が前記配線パッド２の位置に対応して設けられている。この結果、前記配線パッド２の位置に倣って、右側Ｒにおける開口部５及び７の数は比較的少なく、かつその開口部５及び７間のピッチは比較的粗い。一方、左側Ｌにおける開口部５及び７の数は比較的多く、かつその開口部５及び７間のピッチは比較的微細である。なお、説明の便宜上、前記開口部のうち、スキージ１０の移動方向（矢印イ方向）と開口部の長手方向とがほぼ直角となる第１の開口部（図１６で長手方向が縦になっている縦の開口部）に符号５を付し、また、スキージ１０の移動方向と開口部７の長手方向とがほぼ一致する（平行となる）第２の開口部（図１６で長手方向が横になっている横の開口部）に符号７を付す。
【０００４】
前記電子部品１３は、例えばリード端子１４が４方向に延設されたクォーターフラットパッケージ型（ＱＦＰ型）である。
【０００５】
そして、上述の配線パッド２及び前記開口部５及び７の形状は、実装する電子部品１３のリード端子１４に倣って、上面から見て細長い形状をなす。例えば、図１６中に示すように、リード端子１４の延設方向側が長辺で、リード端子１４の横列方向側が短辺であるほぼ長方形形状をなす。
また、前記開口部５及び７の大きさは、後述するはんだペースト９が前記配線パッド２からにじみ出ない（はみ出さない）程度に、前記配線パッド２より一回り小さい。
さらに、上述の配線パッド２と前記開口部５及び７は、図１６に示すように、前記ＱＦＰ型の電子部品１３のリード端子１４に倣って、横列状態（配線パッド２と開口部５及び７が短辺の方向に配列された状態）でロの字形状に配列されている。
【０００６】
４は前記メタルマスク３の他面（図１７中上面で、前記スキージ１０が移動する側の面）側に設けた凹面部である。この凹面部４は、左側Ｌの微細ピッチ側の開口部５及び７群全体を囲う領域範囲内に四角形に設けられている。この結果、左側Ｌの微細なピッチ側の開口部５及び７の深さは、右側Ｒの開口部５及び７の深さより浅くなる。この開口部５及び７の深さは、前記配線パッド２上に印刷されるはんだペースト９の量を決定するものである。すなわち、開口部５及び７の深さが浅ければ、印刷されるはんだペースト９の量が小となる。従って、左側Ｌの微細なピッチ側の配線パッド２上に印刷されるはんだペースト９の量は、右側Ｒの配線パッド２上に印刷されるはんだペーストの量９より小となる。
【０００７】
８は前記メタルマスク３上に置かれたはんだペ−スト、９は前記開口部５及び７を介して前記配線パッド２上に印刷されたはんだペ−ストである。
【０００８】
次に、上述の構成からなるスクリーン印刷機の操作作動について説明する。
まず、スキージ１０が矢印イで示す方向に移動されることによって、メタルマスク３の他面（上面）側であってスキ−ジ１０の前面（スキージ１０の移動方向イを前方としたときのスキージ１０の移動方向側の面）に置かれたはんだペ−スト８は、スキ−ジ１０からメタルマスク３の表面でプリント配線板１に向かう方向の作用力と表面上での回転力を受けて、開口部５、７を介して配線パッド２上にはんだペ−スト９として印刷される。
次に、メタルマスク３をプリント配線板１から離した後、図示していない部品搭載機、所謂、マウンタで各配線パッド２上のはんだペ−スト９上に電子部品１３のリード端子１４をマウントしてから、リフロ−炉を通過されることにより、はんだペースト９は溶融される。その後、冷却されて電子部品１３がプリント配線板１にはんだペースト９を介して固着されたプリント基板１ができあがる。なお、このようなスクリーン印刷機を示したものとして、特開平４−２０１３８９号公報などがある。
【０００９】
【発明が解決しようとする課題】
ところが、上述の従来のスクリーン印刷機においては、スキ−ジ１０によりはんだペ−スト９を縦の開口部５に圧入する印刷状況と横の開口部７に圧入する印刷状況とが以下説明するように異なるために、配線パッド２上に印刷されるはんだペ−スト９にかすれやにじみを生じることがある。特に、図１８の左側Ｌの領域の微細ピッチの縦の開口部５と横の開口部７とにおいて上述のかすれやにじみが発生し易い。以下、上述の縦の開口部５の印刷状況と横の開口部７の印刷状況との相違を詳細に説明する。
【００１０】
図１８（ａ）乃至（ｄ）及び図２０は前記縦の開口部５における印刷状況を示す。
まず、図１８（ａ）及び図２０に示すように、スキ−ジ１０が縦の開口部５の長辺５０を通過した直後に、そのスキ−ジ１０の先端が縦の開口部５中に入り込んで、縦の開口部５中へのはんだペースト９の圧入が開始される。
ここで、この縦の開口部５の短辺５１がスキ−ジ１０の移動方向イとほぼ一致するため、スキ−ジ１０の移動方向イにおける縦の開口部５の隙間の寸法が小である。このために、図１８（ｂ）に示すように、上述のはんだペ−スト９の圧入が直ちに完了する。
しかし、上述のはんだペ−スト９の圧入が直ちに完了しても、縦の開口部５においてはスキ−ジ１０の通過が続いているので、はんだペースト９を縦の開口部５中へさらに充填しようとする圧入力も引続き存在し、その圧入力を受けるはんだペースト９が縦の開口部５中において逃げ場を失って縦の開口部５の長辺（スキ−ジ１０が入り込む側の長辺と反対側の長辺）５０を圧迫する。
また、この縦の開口部５の長辺５０がスキ−ジ１０の先端に対してほぼ平行であるため、図２０中の矢印に示すように、スキ−ジ１０の先端が長辺５０に沿って縦の開口部５中に入り込み易い。このために、スキ−ジ１０によりはんだペ−スト９を縦の開口部５中に圧入しようとする力が大であり、上述の縦の開口部５中において逃げ場を失ったはんだペ−スト９が縦の開口部５の長辺５０を圧迫する力も大となる。
その結果、メタルマスク３とスキ−ジ１０には押し上げる反作用が働き、図１８（ｃ）に示すように、配線パッド２とメタルマスク３の密着性が損なわれ、その箇所ではんだペスート９が洩れだして、印刷されたはんだペ−スト９は厚く幅が広いものとなり、所望のパタ−ンからすればにじみ９０を生じたものとなっている。
そして、開口部の微細化が一層進み、隣接する縦の開口部５間の距離が短くなるほど、その縦の開口部５間のメタルマスク３の部分３０の平面を保とうとする力が小となり、そのメタルマスク３の部分３０と配線パッド２との密着性がさらに損われ、そのメタルマスク３の部分３０が配線パッド２から離れ易くなり、上述のにじみ９０が増す傾向を示す。その結果、図１８（ｄ）に示すように、そのにじみ９０は隣接した配線パッド２間を短絡するので、縦の開口部５の微細化は予想以上に困難である。
【００１１】
一方、図１９（ａ）乃至（ｄ）及び図２１は横の開口部７における印刷状況を示す。
まず、図１９（ａ）及び図２１に示すように、スキ−ジ１０が横の開口部７の短辺７１を通過した直後に、そのスキ−ジ１０により横の開口部７中へのはんだペースト９の圧入が開始される。
ここで、この横の開口部７の長辺７０がスキ−ジ１０の移動方向イとほぼ一致するため、スキ−ジ１０の移動方向イにおける横の開口部７の隙間の寸法が大である。このために、図１９（ｂ）に示すように、スキ−ジ１０が横の開口部７の短辺７１を通過した後にも上述のはんだペ−スト９の圧入は終了せず、スキ−ジ１０の移動に合わせてはんだペースト９の圧入が続けられる。この場合、圧入力を受けるはんだペースト９はスキ−ジ１０の移動方向イでメタルマスク３上に逃げることができ、はんだペ−スト９が開口部７の短辺７１を圧迫することは少ない。
また、この横の開口部７の短辺７１がスキ−ジ１０の先端に対してほぼ平行であるため、図２１中の矢印に示すように、スキ−ジ１０の先端が上述の縦の開口部５と比較してこの横の開口部７中に入り込み難い。このために、スキ−ジ１０によりはんだペ−スト９をこの横の開口部７中に圧入する力は上述の縦の開口部５と比較して小である。
この結果、メタルマスク３やスキ−ジ１０を押し上げる力は殆ど発生せず、図１９（ｃ）及び（ｄ）に示すように、配線パッド２とメタルマスク３の密着性は良好で、厚さならびに幅が所望の形であるにじみのないはんだペ−スト９の印刷を得ることができる。
そして、開口部の微細化が一層進み、隣接する横の開口部７間の距離が短くなっても、上述のメタルマスク３やスキ−ジ１０を押し上げる力は殆ど発生せず、にじみのないはんだペ−スト９が得られる。
【００１２】
もし、ここで、縦の開口部５において所望のはんだペ−スト９の印刷が得られるように、スキ−ジ１０によるはんだペ−スト９の圧入力を減少させたりすると、横の開口部７におけるはんだペ−スト９の圧入力が小さくなってかすれを生じる場合がある。
【００１３】
このように、印刷パタ−ンの微細化と印刷精度の向上は相反した要求となっている。
【００１４】
本発明の目的は、微細なピッチに配列されている開口部においてもかすれやにじみが生じること無くはんだペーストを印刷することができるスクリーン印刷機を提供することにある。
【００１５】
【課題を解決するための手段】
本発明は、前記目的を達成するため、スクリーンマスクの他面側には凹面部が設けられて当該凹面部によって肉薄部と肉厚部とが形成され、開口部の長手方向と前記スキ−ジの移動方向とがほぼ直角である複数のその開口部は各開口部の長手方向が平行となるように横列に整列させた状態で前記肉薄部に配列されており、それらの開口部の両短辺と対向するように前記肉薄部と前記肉厚部とにより形成された段差部があり、それらの開口部の両短辺と対向する段差部を、前記スキージを変形させてそのスキージによる前記はんだペーストを開口部の長手方向と前記スキ−ジの移動方向とがほぼ直角であるその開口部の中へ圧入するための圧入力を軽減させるスキージ変形手段となし、かつ、前記横列に整列されたそれらの開口部のうち両端に位置する開口部より外側の位置においてそれぞれ前記スキージ変形手段と同厚で前記スキージの移動方向とほぼ直角な方向に前記スキージ変形手段から前記肉薄部に張り出した張出部を、前記スキージが移動方向に対して傾斜した姿勢で移動した場合にそのスキージを前記スキージ変形手段による変形状態とほぼ同様に変形させる傾斜用スキージ変形手段となすことを特徴とする。
【００１６】
【作用】
本発明は、縦の開口部の周縁部分の肉薄部と、その縦の開口部の両短辺の近傍部分の肉厚部とにより、スクリーンマスクの他面側において段差部が構成される。この段差部により、スキージが肉厚部において大きく変形しかつ肉薄部において小さく変形する。このために、肉薄部においてスキージがはんだペーストを縦の開口部中に圧入する力を軽減させることができる。この結果、縦の開口部における圧入力を、その圧入力より小に作用する横の開口部（開口部の長手方向とスキ−ジの移動方向とがほぼ平行である開口部）における圧入力に合わせることができる。すなわち、縦の開口部における印刷状況を横の開口部における印刷状況に合わせることができるので、微細なピッチに配列されている縦の開口部及び横の開口部においてかすれやにじみが生じること無くはんだペーストを印刷することができる。
【００１７】
また、本発明は、肉薄部の他面側に肉厚部から肉薄部に一体に張り出した張出部により、スキージが移動方向に対して傾斜した姿勢で移動した場合にそのスキージが上述の段差部による変形状態とほぼ同様の状態に変形する。この結果、スキージが移動方向に対して傾斜した姿勢で移動した場合であっても、そのスキージは確実に変形し、スキージが特に縦の開口部において変形しないときのかすれやにじみが生じるような虞が無い。
【００１８】
【実施例】
以下、本発明のスクリーン印刷機の実施例のうちの２例を図１乃至図７及び図９乃至１５を参照して具体的に説明する。
図１乃至図７は本発明のスクリーン印刷機の第１の実施例を示す。図中、図１６乃至図２１と同符号は同一のものを示す。
図において、１２は凹面部である。この凹面部１２は、メタルマスク３の他面側に、特に左側Ｌの微細ピッチ側の複数個の縦の開口部５及び複数個の横の開口部７全体を囲う領域範囲内にロの字形状に設けられている。この凹面部１２の部分のうち特に前記縦の開口部５の周縁部分を肉厚Ｈ２の肉薄部１１ｃとなし、この凹面部１２の両側の部分のうち特に前記縦の開口部５の両短辺５１の近傍部分を肉厚Ｈ１の肉厚部１１ａ（前記縦の開口部５の外側の肉厚部）及び肉厚部１１ｂ（前記縦の開口部５の内側の肉厚部）となし、この凹面部１２の他面側のうち特に前記縦の開口部５の両短辺５１のうち少なくとも何れか一方、この例では前記縦の開口部５の内側の短辺５１から前記内側の肉厚部１１ｂまでの前記肉薄部１１ｃの他面側をスキージ１０が接触する接触面部１１ｄとなし、この凹面部１２の他面側のうち前記内側の肉厚部１１ｂの４角（４隅）から前記肉薄部１１ｃの他面側に一体にほぼ垂直に張り出した部分を肉厚Ｈ１の張出部１１ｅとなす。この結果、内側の肉厚部１１ｂは、スキ−ジ１の移動方向イに見てＩあるいは工字状（開口部５側からの図示の形で云えばＨ字状）の形状となっている。
【００１９】
そして、上述の凹面部１２によって肉厚部１１ａ及び１１ｂと肉薄部１１ｃとの境界に形成される段差部１２０は、スキージ１０を変形させてそのスキージ１０によるはんだペースト９の縦の開口部５中への圧入力を軽減させるスキージ変形手段を構成する。また、上述の接触面部１１ｄは、スキージ１０によりはんだペースト９を縦の開口部５中に長手方向に圧入できる圧入力が得られるスキージ接触手段を構成する。さらに、上述の張出部１１ｅは、スキージ１０が図１に示すように移動方向イに対して傾斜した姿勢で移動した場合にそのスキージ１０を前記スキージ変形手段（段差部１２０）による変形状態とほぼ同様に変形させる傾斜用スキージ変形手段を構成する。
【００２０】
なお、上述のロ形状の凹面部１２は、前記左側Ｌの微細ピッチ側の複数個の縦の開口部５及び複数個の横の開口部７の深さ、すなわち配線パッド２上に印刷されるはんだペースト９の量を少なく規制するものである。
【００２１】
図３は詳細な寸法関係を示したメタルマスク３の一部平面図である。この図において、スキ−ジ１０が移動する方向での肉厚部１１ｂの長さＸ２は、複数個の縦の開口部５のうち両端に位置する開口部５Ａの外側の長辺５０同士の距離Ｘ１より大きく、内側の肉厚部１１ｂを挾んで位置する横の開口部７の内側の短辺７１同士の距離Ｘ３より小さい。そして、スキ−ジ１０が移動する方向イで幅Ｘ４をもつ張出部１１ｅは、両端に位置する縦の開口部５Ａの外側の長辺５０と横の開口部７の内側の短辺７１との間に位置されている。また、スキ−ジ１０の移動方向イとほぼ直角な方向での張出部１１ｅの長さＹ２は、内側の肉厚部１１ｂを挾んで位置する縦の開口部５の内側の短辺５１同士の距離Ｙ１より小さく、複数個の横の開口部７のうち両端に位置する開口部７の外側の長辺７０同士の距離Ｙ３より大きい。そして、スキ−ジ１０の移動方向イとほぼ直角な方向での内側の肉厚部１１ｂの長さをＹ４とすると、本発明者らの実験によれば、Ｙ４≒（０．２〜０．６）×Ｙ１の任意の値を選択することによって良好な印刷結果が得られている。
【００２２】
この実施例における本発明のスクリーン印刷機は、上記の如き構成からなり、以下その操作作用について説明する。
まず、スキージ１０が矢印イで示す方向に移動されることによって、メタルマスク３の他面側であってスキ−ジ１０の前面に置かれたはんだペ−スト８は、スキ−ジ１０からメタルマスク３の表面でプリント配線板１に向かう方向の作用力と表面上での回転力を受けて、複数個の縦の開口部５及び複数個の横の開口部７を介して配線パッド２上にはんだペ−スト９として印刷される。
【００２３】
このとき、縦の開口部５において、その縦の開口部５の周縁部分の肉薄部１１ｃと、その縦の開口部５の両短辺５１の近傍部分の肉厚部１１ａ及び１１ｂとで構成される段差部１２０により、肉厚部１１ａ及び１１ｂにおいて図４中の実線に示すようにスキージ１０の先端が大きく変形し、かつ肉薄部１１ｃにおいて図４中の二点鎖線に示すようにスキージ１０が小さく変形する。このために、肉薄部１１ｃにおいてスキージ１０がはんだペースト９を縦の開口部５中に圧入する力を軽減させることができる。
この結果、縦の開口部５における圧入力を、その圧入力より小に作用する横の開口部７における圧入力に合わせることができる。すなわち、図５（ａ）乃至（ｃ）に示す縦の開口部５における印刷状況を、図６（ａ）乃至（ｃ）に示す横の開口部７における印刷状況に合わせることができるので、微細なピッチに配列されている縦の開口部５及び横の開口部７においてかすれやにじみが生じること無くはんだペースト９を印刷することができる。
ここで、縦の開口部５における印刷状況と横の開口部７における印刷状況とを図５（ａ）乃至（ｃ）及び図６（ａ）乃至（ｃ）を参照して説明する。
まず、図５（ａ）に示すように、スキージ１０が縦の開口部５の長辺５０を通過した後であっても、上述の変形状態にあるスキージ１０の先端が縦の開口部５中に深く入り込まず、その分はんだペースト９を縦の開口部５中に圧入する力が小となる。このために、図５（ｂ）に示すように、はんだペースト９が瞬時に縦の開口部５中全体に圧入されず、スキ−ジ１０の移動につれてはんだペースト９の圧入区域が広がる。その状況は、図６（ａ）及び（ｂ）に示す横の開口部７と同様で、メタルマスク３やスキ−ジ１０を押し上げるような反作用力は働かない。従って、図５（ｃ）と図６（ｃ）とで対比して示すように、縦の開口部５と横の開口部７の方向性を問わずに、厚さの不揃いやにじみやかすれがなくはんだ９を印刷することができる。
【００２４】
また、この実施例における本発明のスクリーン印刷機は、凹面部１２の他面側のうち内側の肉厚部１１ｂの４角（４隅）から肉薄部１１ｃの他面側に一体にほぼ垂直に張り出した部分を肉厚Ｈ１の張出部１１ｅとなしたものであるから、図１及び図３中の二点鎖線に示すように、スキージ１０が移動方向イに対して傾斜した姿勢で移動した場合に、そのスキージ１０が前記張出部１１ｅにより上述の段差部１２０（スキージ変形手段）による変形状態とほぼ同様の状態に変形する。この結果、スキージ１０が移動方向イに対して傾斜した姿勢で移動した場合であっても、そのスキージ１０の先端は上述のように確実に変形するので、スキージ１０が特に縦の開口部５において変形しないときのかすれやにじみが生じるような虞が無い。
ここで、上述の本発明の張出部１１ｅを具備しないメタルマスク３においてスキージ１０が移動方向イに対して傾斜した姿勢で移動した場合にかすれやにじみが生じる原因について説明する。すなわち、図３中の二点鎖線に示すように、スキージ１０は外側の肉厚部１１ａにかかっているが、内側の肉厚部１１ｂにかかっていないので、そのスキージ１０の先端は内側の肉厚部１１ｂが無い従来のスクリーン印刷機のメタルマスク３での変形状態と同様の状態に変形するだけとなり、その結果、特に複数個の縦の開口部５のうち端の開口部５においてはスキージ１０が充分に変形せず、かすれやにじみが生じる虞があるのである。しかし、本発明のスクリーン印刷機は、上述の張出部１１ｅを具備するので、上述のかすれやにじみが生じる虞が無い。
【００２５】
そして、図１及び図３中の二点鎖線に示すように、スキ−ジ１０が移動方向イに対して斜めになるのは、意図するとせざるとに係らず、加工精度や取付け時の遊びで僅かに斜めになり、本発明者らの実測では、１〜３度の傾斜は常に観測されており、そのために複数個の縦の開口部５のうち両端の開口部５Ａでは、張出部１１ｅがあることによって、必ず、スキ−ジ１０の先端は、肉厚部１１ａ及び１１ｂで変形されている。電子部品のリ−ド端子の配置によっては、２０度位までの傾きを付けることが考えられるが、この場合でも本発明のスクリーン印刷機は上述のかすれやにじみが生じる虞が無い。
【００２６】
さらに、この実施例における本発明のスクリーン印刷機は、縦の開口部５の内側の短辺５１から内側の肉厚部１１ｂまでの肉薄部１１ｃの他面側をスキージ１０が接触する接触面部１１ｄとなしたものであるから、、スキ−ジ１０がその接触面部１１ｄに接触してはんだペースト９を縦の開口部５中に長手方向に圧入できる圧入力が得られる。この結果、図７に示すように、縦の開口部５の外側の短辺５１側の肉薄部１１ｃの他面側に、スキ−ジ１０が接触せずはんだペ−スト９に圧入力が作用しないデッドスペースＤＳが形成されたとしても、縦の開口部５の内側の短辺５１側の肉薄部１１ｃ（接触面部１１ｄ）の他面側にスキ−ジ１０が接触してはんだペ−スト９を縦の開口部５中に長手方向にデッドスペースＤＳ側（縦の開口部５の外側の短辺５１側）まで圧入することができるので、はんだペ−スト９を確実に印刷することができる。
このとき、図８に示すように、縦の開口部５の両短辺５１の肉薄部１１ｃの他面側にデッドスペースＤＳが形成されると、はんだペースト９を縦の開口部５中に圧入する圧入力が得られないので、その縦の開口部５の両短辺部分にはんだペースト９が圧入されない等の問題がある。この実施例における本発明のスクリーン印刷機は、上述の問題を解決することができる。
そして、この実施例における本発明のスクリーン印刷機において、上述の接触面部１１ｄは、上述の例の縦の開口部５の内側の短辺５１側の肉薄部１１ｃの他面側に設けたが、縦の開口部５の外側の短辺５１側の肉薄部１１ｃの他面側、又は縦の開口部５の両短辺５１側の肉薄部１１ｃの他面側に設けても良い。
【００２７】
図９乃至図１２は肉厚部１１ａ及び１１ｂや張出部１１ｅや凹面部１２の形状の変形例を示したメタルマスク３の一部平面図である。
メタルマスク３に対する凹面部１２の形成に関しては、図９及び図１０に示すように凹面部１２（段差部１２０）の角部を丸くしたり面取りを施して加工作業を容易にすると良い。
なお、図１０において、内側の肉厚部１１′ｂは細長い２個のコの字形状をなすものであるが、二点鎖線に示すように１個のＩやエの字形状のもの（１１ｂ）であっても良い。
また、凹面部１２（段差部１２０）の角部を丸くする加工を発展させた形として、図１１に示すように、縦の開口部５及び横の開口部７で囲まれた内側の肉厚部１１ｂを鼓やプ−リを横から見た形としても良い。
さらに、図１２に示すように、張出部１１′ｅを、スキ−ジ１０の移動方向イに対して斜めに設けても良い。
【００２８】
図１３及び図１４は本発明のスクリーン印刷機の第２の実施例を示す。図中、図１乃至図１２及び図１６乃至図２１と同符号は同一のものを示す。
上述の第１の実施例のものは電子部品としてリード端子１４が４方向に延設されたクォーターフラットパッケージ型（ＱＦＰ型）の電子部品１３を搭載するものであるが、この第２の実施例のものは電子部品としてはリード端子１４０が２方向に延設されたデュアルライン型の電子部品１３０を縦横に２個搭載するものである。
【００２９】
図１３においてはデュアルライン型の電子部品１３０がスキージ１０の移動方向イに対してほぼ直角方向に上下（縦）に２個搭載されるものであって、また図１４においてはデュアルライン型の電子部品１３０がスキージ１０の移動方向イに左右（横）に２個搭載されるものであって、メタルマスク３に複数個の縦の開口部５と複数個の横の開口部７とがそれぞれ横列状態で２列平行に配列されている。このメタルマスク３の他面側にロの字形状の凹面部１２Ａを前記２列の複数個の縦の開口部５を囲うように設ける。この結果、縦の開口部５の周縁部分に肉薄部１１０ｃが形成され、また縦の開口部５の両短辺５１の近傍部分に外側の肉厚部１１０ａ及び内側の肉厚部１１０ｂがそれぞれ形成され、さらに縦の開口部５の両短辺５１のうち少なくとも何れか一方から前記肉厚部１１０ａ、１１０ｂまでの前記肉薄部１１０ｃの他面側に接触面部１１０ｄが形成され、さらにその上内側の肉厚部１１０ｂの４隅から前記肉薄部１１０ｃの他面側に張出部１１ｅが構成される。
【００３０】
一方、上述の図１３及び図１４において、メタルマスク３の他面側に四角形の凹面部４０を前記２列の複数個の横の開口部７を囲うようにそれぞれ設ける。この第２の実施例のものは上述の第１の実施例のものと同様の作用効果を達成することができる。
【００３１】
図１５（Ａ）及び（Ｂ）は縦の開口部及び横の開口部の変形例を示した説明図である。開口部は、上述の長方形形状のもの（５、７）の他に、（Ａ）に示す長円形状のもの（５Ａ、７Ａ）、（Ｂ）に示す楕円形状のもの（５Ｂ、７Ｂ）等、電子部品１３、１３０のリード端子１４、１４０に倣って細長いものであって良い。
【００３２】
なお、上述の実施例において、張出部１１ｅ、１１′ｅ、１１０ｅは、内側の肉厚部１１ｂ、１１′ｂ、１１０ｂから肉薄部１１ｃ、１１０ｃに一体に張り出したものであるが、外側の肉厚部１１ａ、１１０ａから肉薄部１１ｃ、１１０ｃに一体に張り出しても良いし、又は内外両肉厚部１１ａ、１１０ａ及び１１ｂ、１１′ｂ、１１０ｂから肉薄部１１ｃ、１１０ｃに一体に張り出しても良い。
【００３３】
【発明の効果】
以上説明したように本発明のスクリーン印刷機によれば、スキ−ジの移動方向に対するスクリーンマスクに設けられた開口部の向きによる印刷状況（はんだペ−スト印刷量）の差がなく、微細なピッチにおいてもかすれやにじみを生じることなくはんだペ−ストを印刷することができる。
【図面の簡単な説明】
【図１】本発明のスクリーン印刷機の第１の実施例を示し、スクリーン印刷機の印刷部の平面図である。
【図２】メタルマスク（スクリーンマスク）の要部の一部拡大斜視図である。
【図３】メタルマスク（スクリーンマスク）の要部の一部拡大平面図である。
【図４】図３におけるＩＶ−ＩＶ線断面図である。
【図５】（ａ）及び（ｂ）及び（ｃ）は図３におけるＶ−Ｖ線断面図であって、縦の開口部における印刷状況を示した説明図である。
【図６】（ａ）及び（ｂ）及び（ｃ）は図３におけるＶＩ−ＶＩ線断面図であって、横の開口部における印刷状況を示した説明図である。
【図７】図３におけるＶＩＩ−ＶＩＩ線断面図である。
【図８】縦の開口部の両短辺側の肉薄部の他面側にデッドスペースが形成された場合の問題点を示した説明図である。
【図９】縦の開口部の段差部の角の形状を変えたメタルマスクの変形例を示した一部平面図である。
【図１０】縦の開口部の段差部の角の形状や内側の肉厚部の形状を変えたメタルマスクの変形例を示した一部平面図である。
【図１１】縦の開口部の内側の肉厚部の形状を変えたメタルマスクの変形例を示した一部平面図である。
【図１２】縦の開口部の内側の肉厚部の形状を変えたメタルマスクの変形例を示した一部平面図である。
【図１３】本発明のスクリーン印刷機の第２の実施例を示し、スクリーン印刷機の印刷部の平面図である。
【図１４】本発明のスクリーン印刷機の第２の実施例の変形例を示し、スクリーン印刷機の印刷部の平面図である。
【図１５】（Ａ）は長円形状の開口部を示した説明図、（Ｂ）は楕円形状の開口部を示した説明図である。
【図１６】従来のスクリーン印刷機の印刷部の拡大平面図である。
【図１７】図１８におけるＡ−Ａ線断面図である。
【図１８】（ａ）及び（ｂ）及び（ｃ）及び（ｄ）は図１８におけるＢ−Ｂ線断面図であって、縦の開口部における印刷状況を示した説明図である。
【図１９】（ａ）及び（ｂ）及び（ｃ）及び（ｄ）は図１８におけるＣ−Ｃ線断面図であって、横の開口部における印刷状況を示した説明図である。
【図２０】図１８におけるＤ−Ｄ線断面図である。
【図２１】図１８におけるＥ−Ｅ線断面図である。
【符号の説明】
１…プリント配線板、２…配線パッド、３…メタルマスク（スクリーンマスク）、４…薄肉部、５…縦の開口部、５０…長辺、５１…短辺、７…横の開口部、８及び９…はんだペ−スト、１０…スキ−ジ、１１ａ及び１１０ａ…外側の肉厚部、１１ｂ及び１１′ｂ及び１１０ｂ…内側の厚肉部、１１ｃ及び１１０ｃ…肉薄部、１１ｄ及び１１０ｄ…接触部、１１ｅ及び１１′ｅ及び１１０ｅ…張出部、１２及び１２Ａ…凹面部、１３…クォーターフラットパッケージ型の電子部品、１３０…デュアルライン型の電子部品、１４及び１４０…リード端子。[0001]
[Industrial application fields]
In the present invention, a printed wiring board is disposed on one side of the screen mask, and the squeegee is moved on the other side of the screen mask, thereby pressing the solder paste against the other side of the screen mask, The present invention relates to a screen printer that prints the solder paste in the form of the opening on the printed wiring board through the opening provided in the screen mask, and in particular, even in the opening arranged in a fine pitch, blurring and blurring. The present invention relates to a screen printing machine capable of printing a solder paste without causing the above.
[0002]
[Prior art]
Solder paste can be printed on a printed wiring board using a screen printer to mount (adhere) electronic components such as semiconductor devices, resistors, capacitors, etc. on the printed wiring board to realize a required electronic circuit. Has been done.
This type of conventional screen printing machine will be described with reference to FIGS.
16 to 21, reference numeral 1 denotes a printed wiring board. The printed wiring board 1 includes a plurality of wiring pads 2 on which a solder paste 9 described later is printed.
This wiring pad 2 is connected to a lead terminal 14 of an electronic component 13 described later via a solder paste 9 described later, and is disposed following the lead terminal 14 of the electronic component 13 to be mounted. For example, in FIG. 16 and FIG. 17, the number of lead terminals 14R of the electronic component 13R mounted on the right side R is relatively small and the pitch between the lead terminals 14R is relatively coarse. The number of 2 is relatively small, and the pitch between the wiring pads 2 is relatively coarse. On the other hand, since the number of lead terminals 14L and the like of the electronic component 13L mounted on the left side L is relatively large and the pitch between the lead terminals 14L is relatively fine, the number of wiring pads 2 on the left side L is compared. The pitch between the wiring pads 2 is relatively fine.
[0003]
Reference numeral 3 denotes a screen mask made of metal, for example, disposed so that one surface (the lower surface in FIG. 17) faces the upper surface of the printed wiring board 1. The metal mask 3 is provided with a plurality of openings 5 and 7 corresponding to the positions of the wiring pads 2. As a result, following the position of the wiring pad 2, the number of openings 5 and 7 on the right side R is relatively small, and the pitch between the openings 5 and 7 is relatively coarse. On the other hand, the number of openings 5 and 7 on the left side L is relatively large, and the pitch between the openings 5 and 7 is relatively fine. For convenience of explanation, among the openings, a first opening (the longitudinal direction is vertical in FIG. 16) in which the moving direction of the squeegee 10 (the direction of arrow A) and the longitudinal direction of the opening are almost perpendicular to each other. The second opening (the longitudinal direction is horizontal in FIG. 16) is denoted by reference numeral 5 and the moving direction of the squeegee 10 and the longitudinal direction of the opening 7 are substantially coincident (parallel). Reference numeral 7 is attached to the horizontal opening).
[0004]
The electronic component 13 is, for example, a quarter flat package type (QFP type) in which lead terminals 14 are extended in four directions.
[0005]
The wiring pads 2 and the openings 5 and 7 described above have elongated shapes as viewed from the top, following the lead terminals 14 of the electronic component 13 to be mounted. For example, as shown in FIG. 16, the lead terminal 14 has a substantially rectangular shape in which the extending direction side is a long side and the row direction side of the lead terminal 14 is a short side.
The sizes of the openings 5 and 7 are slightly smaller than the wiring pads 2 to the extent that solder paste 9 described later does not ooze out (do not ooze out) from the wiring pads 2.
Further, as shown in FIG. 16, the wiring pad 2 and the openings 5 and 7 described above are in a row state (the wiring pad 2 and the openings 5 and 7 according to the lead terminals 14 of the QFP electronic component 13). Are arranged in the direction of the short side).
[0006]
Reference numeral 4 denotes a concave portion provided on the other side of the metal mask 3 (the upper side in FIG. 17 and the side on which the squeegee 10 moves). The concave surface portion 4 is provided in a quadrangular shape within the region surrounding the entire opening 5 and 7 group on the fine pitch side on the left side L. As a result, the depths of the fine pitch side openings 5 and 7 on the left side L are shallower than the depths of the right side R openings 5 and 7. The depths of the openings 5 and 7 determine the amount of the solder paste 9 printed on the wiring pad 2. That is, if the depth of the openings 5 and 7 is shallow, the amount of solder paste 9 to be printed becomes small. Therefore, the amount of solder paste 9 printed on the left side L fine pitch side wiring pad 2 is smaller than the amount 9 of solder paste printed on the right side R wiring pad 2.
[0007]
8 is a solder paste placed on the metal mask 3, and 9 is a solder paste printed on the wiring pad 2 through the openings 5 and 7.
[0008]
Next, the operation of the screen printing machine having the above-described configuration will be described.
First, by moving the squeegee 10 in the direction indicated by the arrow A, the squeegee is located on the other surface (upper surface) side of the metal mask 3 and on the front surface of the squeegee 10 (when the moving direction I of the squeegee 10 is forward). The solder paste 8 placed on the movement direction side of the surface 10 receives the acting force in the direction from the squeegee 10 toward the printed wiring board 1 on the surface of the metal mask 3 and the rotational force on the surface. The solder paste 9 is printed on the wiring pad 2 through the openings 5 and 7.
Next, after separating the metal mask 3 from the printed wiring board 1, the lead terminals 14 of the electronic components 13 are mounted on the solder paste 9 on each wiring pad 2 by a component mounting machine (not shown), that is, a mounter. Then, the solder paste 9 is melted by passing through a reflow furnace. Thereafter, the printed circuit board 1 is completed by being cooled and having the electronic component 13 fixed to the printed wiring board 1 via the solder paste 9. An example of such a screen printer is disclosed in Japanese Patent Laid-Open No. 4-201389.
[0009]
[Problems to be solved by the invention]
However, in the above-described conventional screen printing machine, the printing situation in which the solder paste 9 is press-fitted into the vertical opening 5 by the squeegee 10 and the printing situation in which the solder paste 9 is press-fitted into the horizontal opening 7 will be described below. Therefore, the solder paste 9 printed on the wiring pad 2 may be blurred or smeared. In particular, the above-mentioned blurring and blurring are likely to occur in the vertical opening 5 and the horizontal opening 7 having a fine pitch in the region on the left side L in FIG. Hereinafter, the difference between the printing situation of the vertical opening 5 and the printing situation of the horizontal opening 7 will be described in detail.
[0010]
FIGS. 18A to 18D and FIG. 20 show the printing situation in the vertical opening 5.
First, as shown in FIG. 18A and FIG. Long side 50 Immediately after passing, the tip of the squeegee 10 enters the vertical opening 5 and press-fitting of the solder paste 9 into the vertical opening 5 is started.
Here, the vertical opening 5 Short side 51 Is substantially coincident with the moving direction A of the squeegee 10, and therefore the size of the gap of the vertical opening 5 in the moving direction I of the squeegee 10 is small. For this reason, as shown in FIG. 18B, the press-fitting of the solder paste 9 is immediately completed.
However, even if the press-in of the solder paste 9 is immediately completed, the squeegee 10 continues to pass through the vertical opening 5, so that the solder paste 9 is further filled into the vertical opening 5. The pressure input to be continued also exists, and the solder paste 9 that receives the pressure input loses escape in the vertical opening 5 and the long side of the vertical opening 5 (the long side on the side into which the squeegee 10 enters) The long side 50 on the opposite side is pressed.
Further, since the long side 50 of the vertical opening 5 is substantially parallel to the tip of the squeegee 10, the tip of the squeegee 10 extends along the long side 50 as shown by the arrow in FIG. And easily enter the vertical opening 5. For this reason, the force that tries to press-fit the solder paste 9 into the vertical opening 5 by the squeegee 10 is large, and the solder paste 9 that has lost the escape field in the vertical opening 5 described above. However, the force which presses the long side 50 of the vertical opening part 5 also becomes large.
As a result, a push-up reaction acts on the metal mask 3 and the squeegee 10, and as shown in FIG. 18C, the adhesion between the wiring pad 2 and the metal mask 3 is impaired, and the solder paste 9 leaks at that location. However, the printed solder paste 9 is thick and wide, and a blur 90 is generated from a desired pattern.
And as the miniaturization of the opening further progresses and the distance between the adjacent vertical openings 5 becomes shorter, the force to keep the plane of the portion 30 of the metal mask 3 between the vertical openings 5 becomes smaller, The adhesion between the portion 30 of the metal mask 3 and the wiring pad 2 is further impaired, and the portion 30 of the metal mask 3 is easily separated from the wiring pad 2, and the above-described blur 90 tends to increase. As a result, as shown in FIG. 18 (d), the blur 90 short-circuits between adjacent wiring pads 2, so that the vertical opening 5 is more difficult than expected.
[0011]
On the other hand, FIGS. 19A to 19D and FIG. 21 show a printing state in the horizontal opening 7.
First, as shown in FIGS. 19A and 21, immediately after the squeegee 10 passes through the short side 71 of the lateral opening 7, the solder into the lateral opening 7 by the squeegee 10 is used. The press-fitting of the paste 9 is started.
Here, since the long side 70 of the horizontal opening 7 substantially coincides with the moving direction A of the squeegee 10, the size of the gap of the horizontal opening 7 in the moving direction I of the squeegee 10 is large. . For this reason, as shown in FIG. 19B, even after the squeegee 10 passes through the short side 71 of the lateral opening 7, the press-fitting of the solder paste 9 is not completed, and the squeegee is not completed. The solder paste 9 is press-fitted in accordance with the movement of 10. In this case, the solder paste 9 receiving the pressure input can escape onto the metal mask 3 in the moving direction of the squeegee 10, and the solder paste 9 is less likely to press the short side 71 of the opening 7.
Further, since the short side 71 of the horizontal opening 7 is substantially parallel to the tip of the squeegee 10, the tip of the squeegee 10 has the above-described vertical opening as shown by the arrow in FIG. Compared with the part 5, it is difficult to enter the side opening 7. For this reason, the force with which the solder paste 9 is press-fitted into the horizontal opening 7 by the squeegee 10 is smaller than that of the vertical opening 5 described above.
As a result, almost no force is generated to push up the metal mask 3 and the squeegee 10, and as shown in FIGS. 19C and 19D, the adhesiveness between the wiring pad 2 and the metal mask 3 is good and the thickness is increased. In addition, it is possible to obtain a print of the solder paste 9 having a desired width and no bleeding.
Even if the opening is further miniaturized and the distance between the adjacent lateral openings 7 is shortened, the force for pushing up the metal mask 3 and the squeegee 10 hardly occurs and the solder does not bleed. A paste 9 is obtained.
[0012]
If the pressure input of the solder paste 9 by the squeegee 10 is reduced so that the desired solder paste 9 can be printed in the vertical opening 5, then the horizontal opening 7. There is a case where the pressure input of the solder paste 9 becomes small and blur occurs.
[0013]
Thus, miniaturization of the printing pattern and improvement of printing accuracy are conflicting requirements.
[0014]
An object of the present invention is to provide a screen printer capable of printing a solder paste without causing blurring or blurring even in openings arranged at a fine pitch.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides A concave portion is provided on the other surface side of the screen mask, and a thin portion and a thick portion are formed by the concave portion, and the longitudinal direction of the opening and the moving direction of the squeegee are substantially perpendicular to each other. The openings are arranged in the thin portions in a state of being aligned in rows so that the longitudinal directions of the openings are parallel, and the thin portions and the thin portions are opposed to both short sides of the openings. There is a step portion formed by the thick portion, and the step portion facing both short sides of the opening is deformed by deforming the squeegee so that the solder paste by the squeegee is disposed in the longitudinal direction of the opening and the squeegee. The squeegee deforming means for reducing press-fitting for press-fitting into the opening that is substantially perpendicular to the direction of movement of the die, and openings located at both ends of the openings aligned in the row In the position outside the section The squeegee is moved in a posture in which the squeegee is inclined with respect to the moving direction, with the protruding portions protruding from the squeegee deforming means to the thin part in a direction substantially perpendicular to the moving direction of the squeegee, each having the same thickness as the squeegee changing means In this case, the squeegee deforms the squeegee deforming means for deforming the squeegee almost in the same manner as the deformed state by the squeegee deforming means. It is characterized by that.
[0016]
[Action]
In the present invention, a stepped portion is formed on the other surface side of the screen mask by the thin portion at the peripheral portion of the vertical opening and the thick portion in the vicinity of both short sides of the vertical opening. By this step portion, the squeegee is greatly deformed at the thick portion and small at the thin portion. For this reason, it is possible to reduce the force with which the squeegee presses the solder paste into the vertical opening in the thin portion. As a result, the pressure input at the vertical opening is changed to the pressure input at the horizontal opening (opening in which the longitudinal direction of the opening and the moving direction of the squeegee are substantially parallel) acting to a smaller extent than the pressure input. Can be matched. That is, since the printing situation in the vertical opening can be matched to the printing situation in the horizontal opening, the solder is not generated in the vertical opening and the horizontal opening arranged in a fine pitch without blurring or blurring. The paste can be printed.
[0017]
Further, according to the present invention, when the squeegee is moved in a posture inclined with respect to the moving direction by the overhanging portion integrally projecting from the thick portion to the thin portion on the other surface side of the thin portion, the squeegee has the above-described step difference. It is deformed to a state substantially similar to the deformed state by the part. As a result, even when the squeegee is moved in a posture inclined with respect to the moving direction, the squeegee is surely deformed, and there is a risk that blurring or blurring may occur when the squeegee is not deformed particularly in the vertical opening. There is no.
[0018]
【Example】
Hereinafter, two examples of the screen printing machine according to the present invention will be described in detail with reference to FIGS. 1 to 7 and FIGS. 9 to 15.
1 to 7 show a first embodiment of a screen printing machine according to the present invention. In the figure, the same reference numerals as those in FIGS. 16 to 21 denote the same components.
In the figure, 12 is a concave surface portion. This concave surface portion 12 is formed in a rectangular shape within the region surrounding the entire plurality of vertical openings 5 and the plurality of horizontal openings 7 on the other surface side of the metal mask 3, particularly on the left-side L fine pitch side. It is provided in the shape. Among the portions of the concave surface portion 12, particularly the peripheral portion of the vertical opening portion 5 is formed as a thin portion 11 c having a thickness H 2, and among the portions on both sides of the concave surface portion 12, particularly both short sides of the vertical opening portion 5. A portion near 51 is formed as a thick portion 11a having a thickness H1 (a thick portion outside the vertical opening 5) and a thick portion 11b (a thick portion inside the vertical opening 5). At least one of the short sides 51 of the vertical opening 5 on the other surface side of the concave surface portion 12, in this example, from the short side 51 inside the vertical opening 5 to the thick part on the inside. The other surface side of the thin portion 11c up to 11b is formed as a contact surface portion 11d with which the squeegee 10 comes into contact, and the thin portion is formed from four corners (four corners) of the inner thick portion 11b on the other surface side of the concave portion 12. A portion projecting substantially vertically integrally with the other surface side of the portion 11c is defined as a projecting portion 11e having a thickness H1. As a result, the thick portion 11b on the inner side is in the shape of I or a work shape (H shape in the illustrated form from the opening 5 side) as seen in the moving direction A of the squeegee 1. .
[0019]
The step portion 120 formed at the boundary between the thick portions 11a and 11b and the thin portion 11c by the concave surface portion 12 deforms the squeegee 10 so that it is in the vertical opening 5 of the solder paste 9 by the squeegee 10. The squeegee deforming means for reducing the pressure input to the is configured. Further, the contact surface portion 11d described above constitutes a squeegee contact means capable of obtaining a pressure input capable of press-fitting the solder paste 9 into the vertical opening 5 by the squeegee 10 in the longitudinal direction. Furthermore, when the squeegee 10 moves in a posture inclined with respect to the moving direction a as shown in FIG. 1, the above-described overhanging portion 11 e causes the squeegee 10 to be in a deformed state by the squeegee deforming means (stepped portion 120). A tilting squeegee deforming means that deforms in substantially the same manner is configured.
[0020]
The above-mentioned concave concave surface portion 12 is printed on the depths of the plurality of vertical openings 5 and the plurality of horizontal openings 7 on the fine pitch side of the left side L, that is, on the wiring pads 2. The amount of the solder paste 9 is restricted to be small.
[0021]
FIG. 3 is a partial plan view of the metal mask 3 showing a detailed dimensional relationship. In this figure, the direction in which the squeegee 10 moves Thickness The length X2 of the part 11b is larger than the distance X1 between the long sides 50 on the outer side of the opening part 5A located at both ends of the plurality of vertical openings 5, and is located on the inner thick part 11b. It is smaller than the distance X3 between the short sides 71 on the inside of the opening 7. The overhanging portion 11e having a width X4 in the direction in which the squeegee 10 moves has a long side 50 outside the vertical opening 5A located at both ends and a short side 71 inside the horizontal opening 7. Is located between. Further, the length Y2 of the overhanging portion 11e in the direction substantially perpendicular to the moving direction A of the squeegee 10 is such that the short sides 51 inside the vertical opening 5 positioned with the inner thick portion 11b interposed therebetween. The distance Y1 is smaller than the distance Y1, and is larger than the distance Y3 between the long sides 70 outside the openings 7 located at both ends of the plurality of horizontal openings 7. Then, assuming that the length of the inner thick portion 11b in the direction substantially perpendicular to the moving direction A of the squeegee 10 is Y4, according to the experiments by the present inventors, Y4≈ (0.2-0. 6) A good printing result is obtained by selecting an arbitrary value of xY1.
[0022]
The screen printing machine of the present invention in this embodiment is configured as described above, and its operation will be described below.
First, when the squeegee 10 is moved in the direction indicated by the arrow A, the solder paste 8 placed on the other surface side of the metal mask 3 and on the front surface of the squeegee 10 is moved from the squeegee 10 to the metal. The surface of the mask 3 receives the acting force in the direction toward the printed wiring board 1 and the rotational force on the surface, and then on the wiring pad 2 through the plurality of vertical openings 5 and the plurality of horizontal openings 7. Is printed as a solder paste 9.
[0023]
At this time, the vertical opening 5 is composed of a thin portion 11 c at the peripheral portion of the vertical opening 5 and thick portions 11 a and 11 b in the vicinity of both short sides 51 of the vertical opening 5. Due to the stepped portion 120, the tip of the squeegee 10 is greatly deformed in the thick portions 11a and 11b as shown by the solid line in FIG. 4, and the squeegee 10 is formed in the thin portion 11c as shown by the two-dot chain line in FIG. Small deformation. For this reason, it is possible to reduce the force with which the squeegee 10 press-fits the solder paste 9 into the vertical opening 5 in the thin portion 11c.
As a result, the pressure input in the vertical opening 5 can be matched with the pressure input in the horizontal opening 7 acting smaller than the pressure input. That is, the printing situation in the vertical openings 5 shown in FIGS. 5A to 5C can be matched with the printing situation in the horizontal openings 7 shown in FIGS. 6A to 6C. It is possible to print the solder paste 9 without causing blurring or blurring in the vertical openings 5 and the horizontal openings 7 arranged at a proper pitch.
Here, the printing situation in the vertical opening 5 and the printing situation in the horizontal opening 7 will be described with reference to FIGS. 5 (a) to 5 (c) and FIGS. 6 (a) to 6 (c).
First, as shown in FIG. 5A, even after the squeegee 10 passes through the long side 50 of the vertical opening 5, the tip of the squeegee 10 in the above-described deformed state is in the vertical opening 5. Therefore, the force to press-fit the solder paste 9 into the vertical opening 5 is reduced accordingly. For this reason, as shown in FIG. 5B, the solder paste 9 is not instantaneously press-fitted into the entire vertical opening 5, and the press-in area of the solder paste 9 is expanded as the squeegee 10 moves. The situation is the same as that of the horizontal opening 7 shown in FIGS. 6A and 6B, and no reaction force that pushes up the metal mask 3 or the squeegee 10 works. Therefore, as shown in FIG. 5 (c) and FIG. 6 (c) in contrast, the thickness unevenness, blurring and blurring are not affected regardless of the directionality of the vertical opening 5 and the horizontal opening 7. Solder 9 can be printed.
[0024]
Further, the screen printing machine of the present invention in this embodiment is substantially perpendicular to the other surface side of the thin portion 11c from the four corners (four corners) of the thick portion 11b on the inside of the concave surface portion 12 on the other surface side. Since the overhanging portion becomes the overhanging portion 11e with the thickness H1, the squeegee 10 has moved in a posture inclined with respect to the moving direction a as shown by the two-dot chain line in FIGS. In this case, the squeegee 10 is deformed by the projecting portion 11e into a state substantially the same as the deformed state by the step 120 (squeegee deforming means). As a result, even when the squeegee 10 moves in a posture inclined with respect to the moving direction a, the tip of the squeegee 10 is reliably deformed as described above. There is no risk of blurring or blurring when not deforming.
Here, a description will be given of the cause of blurring and blurring when the squeegee 10 moves in a posture inclined with respect to the moving direction A in the metal mask 3 that does not include the overhanging portion 11e of the present invention. That is, as shown by the two-dot chain line in FIG. 3, the squeegee 10 is applied to the outer thick portion 11a, but is not applied to the inner thick portion 11b. Only a deformation state similar to the deformation state in the metal mask 3 of the conventional screen printing machine without the thick portion 11b is obtained, and as a result, the squeegee is particularly formed at the end opening 5 of the plurality of vertical openings 5. 10 may not be sufficiently deformed, and there is a risk of blurring or blurring. However, since the screen printing machine of the present invention includes the above-described overhanging portion 11e, there is no possibility that the above-described fading or blurring occurs.
[0025]
As shown by the two-dot chain line in FIGS. 1 and 3, the squeegee 10 is inclined with respect to the moving direction (a), regardless of whether it is intended or not. In the actual measurement by the present inventors, an inclination of 1 to 3 degrees is always observed. Therefore, among the plurality of vertical openings 5, the openings 5A at both ends are overhangs. By having 11e, the tip of the squeegee 10 is always deformed by the thick portions 11a and 11b. Depending on the arrangement of the lead terminals of the electronic component, it is conceivable that the inclination is up to about 20 degrees. However, even in this case, the screen printing machine of the present invention does not have the above-mentioned blur or blur.
[0026]
Furthermore, the screen printing machine of the present invention in this embodiment is configured such that the squeegee 10 contacts the other surface side of the thin portion 11c from the inner short side 51 of the vertical opening 5 to the inner thick portion 11b. As a result, the squeegee 10 comes into contact with the contact surface portion 11d, and a press input is obtained in which the solder paste 9 can be pressed into the vertical opening 5 in the longitudinal direction. As a result, as shown in FIG. 7, the squeegee 10 does not contact the other surface side of the thin part 11 c on the short side 51 side outside the vertical opening 5, and pressure input acts on the solder paste 9. Even if the dead space DS is not formed, the squeegee 10 comes into contact with the other surface side of the thin part 11c (contact surface part 11d) on the short side 51 inside the vertical opening 5, and the solder paste 9 Can be press-fitted into the vertical opening 5 in the longitudinal direction to the dead space DS side (the short side 51 side outside the vertical opening 5), so that the solder paste 9 can be printed reliably. .
At this time, as shown in FIG. 8, when a dead space DS is formed on the other surface side of the thin portion 11 c of both short sides 51 of the vertical opening 5, the solder paste 9 is press-fitted into the vertical opening 5. Therefore, there is a problem that the solder paste 9 is not press-fitted into both short sides of the vertical opening 5. In this example The screen printing machine of the present invention can solve the above-mentioned problems.
And In this example In the screen printing machine of the present invention, the contact surface portion 11d described above is provided on the other surface side of the thin portion 11c on the short side 51 side inside the vertical opening portion 5 in the above example. You may provide in the other surface side of the thin part 11c by the side of the outer short side 51, or the thin film part 11c by the side of the both short sides 51 of the vertical opening part 5.
[0027]
9 to 12 are partial plan views of the metal mask 3 showing modifications of the shapes of the thick portions 11a and 11b, the overhang portion 11e, and the concave portion 12. FIG.
Regarding the formation of the concave surface portion 12 on the metal mask 3, it is preferable to make the corner portion of the concave surface portion 12 (stepped portion 120) round or chamfered as shown in FIGS.
In FIG. 10, the inner thick portion 11′b has two elongated U-shapes. However, as shown by a two-dot chain line, one thick I-shaped or 11-shaped shape (11b ).
Also, the concave surface portion 12 (stepped portion 120 As shown in FIG. 11, the inner thick portion 11b surrounded by the vertical opening 5 and the horizontal opening 7 is tapped with a drum or a pulley. It may be a shape seen from the side.
Further, as shown in FIG. 12, the overhanging portion 11 ′ e may be provided obliquely with respect to the moving direction “a” of the squeegee 10.
[0028]
13 and 14 show a second embodiment of the screen printing machine of the present invention. In the figure, the same reference numerals as those in FIGS. 1 to 12 and FIGS. 16 to 21 denote the same components.
In the first embodiment described above, a quarter flat package type (QFP type) electronic component 13 in which lead terminals 14 are extended in four directions is mounted as an electronic component. As for the electronic component, two dual-line type electronic components 130 each having lead terminals 140 extending in two directions are mounted vertically and horizontally.
[0029]
In FIG. 13, two dual-line electronic components 130 are mounted vertically (vertically) in a direction substantially perpendicular to the moving direction A of the squeegee 10, and in FIG. Two parts 130 are mounted on the left and right (horizontal) in the moving direction of the squeegee 10, and a plurality of vertical openings 5 and a plurality of horizontal openings 7 are arranged in the metal mask 3 respectively. Two rows are arranged in parallel in the state. On the other surface side of the metal mask 3, a square-shaped concave surface portion 12A is provided so as to surround the plurality of vertical openings 5 in the two rows. As a result, a thin portion 110c is formed at the peripheral portion of the vertical opening 5, and an outer thick portion 110a and an inner thick portion 110b are formed in the vicinity of both short sides 51 of the vertical opening 5, respectively. Further, a contact surface portion 110d is formed on the other surface side of the thin portion 110c from at least one of the short sides 51 of the vertical opening 5 to the thick portions 110a and 110b, Overhang portions 11e are formed on the other surface side of the thin portion 110c from the four corners of the thick portion 110b.
[0030]
On the other hand, the above figure 13 And figure 14 4, a rectangular concave surface portion 40 is provided on the other surface side of the metal mask 3 so as to surround the plurality of horizontal openings 7 in the two rows. The thing of this 2nd Example can achieve the effect similar to the thing of the above-mentioned 1st Example.
[0031]
FIGS. 15A and 15B are explanatory views showing modifications of the vertical opening and the horizontal opening. In addition to the rectangular shape (5, 7) described above, the opening has an elliptical shape (5A, 7A) shown in (A), an elliptical shape (5B, 7B) shown in (B), etc. The elongate lead terminals 14 and 140 of the electronic components 13 and 130 may be used.
[0032]
In the above-described embodiment, the overhang portions 11e, 11′e, and 110e are integrally extended from the inner thick portions 11b, 11′b, and 110b to the thin portions 11c and 110c. The thick portions 11a, 110a may be integrally projected to the thin portions 11c, 110c, or the inner and outer thick portions 11a, 110a and 11b, 11'b, 110b may be integrally projected to the thin portions 11c, 110c. good.
[0033]
【The invention's effect】
As described above, according to the screen printing machine of the present invention, there is no difference in the printing situation (solder paste printing amount) depending on the direction of the opening provided in the screen mask with respect to the moving direction of the squeegee, and it is fine. The solder paste can be printed without causing blurring or blurring even on the pitch.
[Brief description of the drawings]
FIG. 1 is a plan view of a printing unit of a screen printing machine according to a first embodiment of the screen printing machine of the present invention.
FIG. 2 is a partially enlarged perspective view of a main part of a metal mask (screen mask).
FIG. 3 is a partially enlarged plan view of a main part of a metal mask (screen mask).
4 is a cross-sectional view taken along line IV-IV in FIG.
FIGS. 5A, 5B, and 5C are cross-sectional views taken along line VV in FIG. 3 and are explanatory diagrams illustrating a printing state in a vertical opening.
6A, 6B, and 6C are cross-sectional views taken along the line VI-VI in FIG. 3 and are explanatory views showing a printing state in a lateral opening.
7 is a cross-sectional view taken along line VII-VII in FIG.
FIG. 8 is an explanatory view showing a problem when a dead space is formed on the other surface side of the thin portion on both short sides of the vertical opening.
FIG. 9 is a partial plan view showing a modification of the metal mask in which the corner shape of the step portion of the vertical opening is changed.
FIG. 10 is a partial plan view showing a modification of the metal mask in which the shape of the corner of the step portion of the vertical opening and the shape of the inner thick portion are changed.
FIG. 11 is a partial plan view showing a modified example of the metal mask in which the shape of the thick portion inside the vertical opening is changed.
FIG. 12 is a partial plan view showing a modification of the metal mask in which the shape of the thick part inside the vertical opening is changed.
FIG. 13 is a plan view of a printing unit of a screen printing machine according to a second embodiment of the screen printing machine of the present invention.
FIG. 14 is a plan view of a printing unit of a screen printing machine, showing a modification of the second embodiment of the screen printing machine of the present invention.
15A is an explanatory view showing an oval opening, and FIG. 15B is an explanatory view showing an oval opening.
FIG. 16 is an enlarged plan view of a printing unit of a conventional screen printing machine.
17 is a cross-sectional view taken along line AA in FIG.
18 (a), (b), (c) and (d) are cross-sectional views taken along the line BB in FIG.
19 (a), (b), (c), and (d) are cross-sectional views taken along the line CC in FIG.
20 is a sectional view taken along line DD in FIG.
FIG. 21 is a cross-sectional view taken along line EE in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Printed wiring board, 2 ... Wiring pad, 3 ... Metal mask (screen mask), 4 ... Thin part, 5 ... Vertical opening part, 50 ... Long side, 51 ... Short side, 7 ... Horizontal opening part, 8 And 9 ... solder paste, 10 ... squeegee, 11a and 110a ... outer thick part, 11b and 11'b and 110b ... inner thick part, 11c and 110c ... thin part, 11d and 110d ... contact 11e and 11'e and 110e ... overhang, 12 and 12A ... concave surface, 13 ... quarter flat package type electronic component, 130 ... dual line type electronic component, 14 and 140 ... lead terminal.

Claims

A printed wiring board is disposed on one side of the screen mask, and the squeegee is moved on the other side of the screen mask so that the solder paste is pressed against the other side of the screen mask and the solder paste is applied. In a screen printer that prints in the form of the opening on the printed wiring board through the opening provided in the screen mask,
Wherein the other surface side of the screen mask concave portion is formed and a thin portion and a thick portion by the concave portion is formed, the a longitudinal opening liked - plurality of the moving direction of di is approximately perpendicular its opening of being arranged on the thin portion in a state where the longitudinal direction of each opening is aligned in rows in parallel, and the thin portion so as to face the two short sides of those openings There is a step portion formed by the thick portion, and the step portion facing both short sides of the opening portion is deformed by deforming the squeegee so that the solder paste by the squeegee is applied to the longitudinal direction of the opening portion and the squeegee. -A squeegee deforming means for reducing press-fitting for press-fitting into the opening which is substantially perpendicular to the direction of movement of the die, and located at both ends of the openings aligned in the row In the position outside the opening The squeegee is moved in a posture in which the squeegee is inclined with respect to the moving direction in a direction that is the same thickness as the squeegee deforming means and is substantially perpendicular to the moving direction of the squeegee. In this case, the screen squeegee is a tilting squeegee deforming means for deforming the squeegee in substantially the same manner as the deformed state by the squeegee deforming means .

The electronic component mounted on the printed wiring board is a quarter flat package type electronic component in which lead terminals are extended in four directions. The screen mask has a substantially perpendicular direction between the longitudinal direction of the opening and the moving direction of the squeegee. A plurality of first openings, and a plurality of second openings in which the longitudinal direction of the openings and the moving direction of the squeegee are substantially parallel, the longitudinal directions of these openings are parallel to each other. The screen masks are arranged in a square shape in a state of being aligned in rows so that the concave portions of the square shape are formed on the other surface side of the screen mask. 2 openings are arranged so as to be arranged in the thin portion, and the stepped portion facing the short sides of the first opening among the stepped portions of the concave surface portion is formed as a squeegee deforming means, and the concave surface Of the other side of the part The first squeegee deforming means are integrated with the squeegee deforming means in a direction substantially perpendicular to the moving direction of the squeegee at the positions outside the openings located at both ends of the first openings arranged in rows. 2. The screen printing machine according to claim 1, wherein the protruding portion serves as a tilting squeegee deforming means.

The electronic component mounted on the printed wiring board is a dual-line type electronic component with lead terminals extending in two directions, and the screen mask has a longitudinal direction of the opening and the direction of movement of the squeegee approximately at right angles. A plurality of first openings, and a plurality of second openings in which the longitudinal direction of the openings and the movement direction of the squeegee are substantially parallel are respectively arranged in two rows in the longitudinal direction of each opening. Are arranged in a row so as to be parallel to each other in a row, and at the other surface side of the screen mask, a square-shaped concave portion is provided, and at least the first opening is the concave portion. Of the stepped portion of the concave surface portion, the stepped portion facing both short sides of the first opening portion as a squeegee deforming means, and the other surface side of the concave surface portion Aligned in the row Among the openings of one, the portions integrally projecting from the squeegee deforming means in the direction substantially perpendicular to the moving direction of the squeegee at the positions outside the openings located at both ends are inclined. The screen printing machine according to claim 1, wherein the screen printing machine is a squeegee deforming means.