【発明の詳細な説明】[Detailed description of the invention]
本発明合金は半導体を要素とするIC、LSI等の
機器のリードフレーム用銅合金、特に耐熱性、曲
げ加工性およびメツキ密着性に優れた銅合金に関
するものである。
一般に半導体を要素とするIC、LSI等の機器は
何れも半導体ペレツトリード、ボンデイングワイ
ヤにより構成されたものをハーメチツクシール、
セラミツクシール技術により封止したものであ
り、種々の型式のものが使用されている。
而して従来これら機器のリードフレーム材とし
ては鉄−ニツケル系材料としてコバール（Fe−
29％Ni−17％Co合金）、42合金、コバールに金を
被覆したクラツド材、鉄−ニツケル合金にAlを
被覆したクラツド材、銅合金としてリン青銅、
C19400（Cu−Fe−Zn−Ｐ合金）、19500（Cu−Fe
−Co−Sn−Ｐ合金）、C14410（Cu−Sn−Ｐ合金）
等が用いられている。しかしながら上記鉄−ニツ
ケル系材料は耐熱性、強度は優れているがコスト
が高いとともに、導電性が悪く、加工性も悪いた
め近時コストが安くかつ加工性、メツキ密着性お
よび半田付性が良好な銅系合金が主流を占めつつ
ある。しかしながら上記の如き銅合金は耐熱性、
電気（熱）的特性、曲げ加工性等が劣るためリー
ドフレーム材として充分な特性を発揮することが
できないものであつた。特に最近のように高密
度、高集積度が強く要求されるところから高い導
電率、強度、曲げ加工性および耐熱性を有し、メ
ツキ加工され易い表面品質を有する材料が必要と
なつて来た。すなわち高信頼性、経済性、
サーマルパフオーマンスというものが現在のリー
ドフレーム材への要求される条件となつているの
である。
メツキ加工され易い表面品質とは半導体ペレツ
トとリードフレーム、ならびにボンデイングワイ
ヤとリードフレームの接続性を向上し、リードフ
レームの耐酸化性、耐腐食性、半田付性等を向上
維持するために行なう金、銀、ニツケル、スズ等
のメツキ被着性が優れていることで、このような
メツキ加工はリードフレームの如き材料において
は加工コスト中、大きな比重を占め品質信頼性に
大きく影響する。
コバール、42合金等の鉄−ニツケル系材料は導
電性、熱伝導性が劣るばかりか、メツキ加工が困
難で特別の工夫を必要とする。例えばこれ等基材
の表面にニツケル層とSn−Ni合金層とを順次被
着した後、該Sn−Ni合金層上に銀層を被着する
か、あるいは基材の表面に銀および銅を含むシア
ンアルカリ性メツキ液にてメツキを施し、その表
面にメツキを行つている。一般にリードフレーム
材用銅合金として次の６項目を満足する材料が強
く要望されている。
(1) 電気および熱の伝導性が良いこと
(2) 耐熱性が良いこと
(3) 曲げ加工性が良いこと
(4) 強度が大きいこと
(5) メツキ密着性が良いこと
(6) 半田付性が良いこと
本発明はこれに鑑み種々研究の結果従来のリー
ドフレーム用銅合金よりも耐熱性、曲げ加工性に
優れ充分な強度とメツキ密着性を有する半導体機
器のリードフレーム用銅合金を開発したもので
Ni0.4〜4.0wt％（以下％と略記）Sn0.5〜5.0％、
Al0.4〜4.0％、Ｐ：0.3％以下を含み残部がCuか
らなる合金に係る。即ち本発明合金はCuを基材
としNi、Sn、Al、Ｐを添加するものであり
NixSny、NixAly、NixPy、SnxPy等の金属間
化合物を微小析出物として析出させることとＰの
添加によつて脱酸の効果を狙つたものであり、さ
らにCu基中にNi、SnおよびAlが固溶することに
より基材の強化を狙つたもので銅合金としてこの
従来の常識を越える強度、耐熱性を有し、良好な
メツキ密着性、半田付性を有するリードフレーム
用銅合金を得たものである。
而して本発明合金においてNi0.4〜4.0％、
Sn0.5〜5.0％Al0.4〜4.0％、P0.3％以下と限定し
た理由はNi0.4％、Sn0.5％Al0.4％、未満では必
要とする強度、耐熱性が得られず、Ni4.0％、
Sn5.0％Al4.0％、P0.3％を越えると強度、耐熱性
において優れた性能が得られるが曲げ加工性が劣
化するばかりでなく、メツキ密着性および半田付
性も劣化するからである。
以下本発明合金を実施例により説明する。
黒鉛るつぼを使用してCuを溶解し、その湯面
を木炭粉末にて覆い十分溶解した後、Ni、Sn、
Al、Ｐの順に添加しこれを鋳造し第１表に示す
組成の幅150mm、長さ200mm、厚さ25mmの鋳塊を得
た次にこの鋳塊の表面を一面あたり2.5mm面削し
た後、熱間圧延を行ない、巾150mm厚さ８mmの板
に冷間圧延と焼鈍を繰り返し加え最終圧延率40％
にて厚さ0.3mmの冷間圧延上がり材を得た。これ
らの板について曲げ加工性、導電率、引張り強
さ、耐熱性、メツキ密着性、半田付性を測定し
た。これらの結果を第１表に示す。なお比較のた
めに従来のリードフレーム用合金についても同様
な測定を行ない、その結果を第１表に併記した。
曲げ加工性は板材より幅５mm、長さ50mmの短冊
型試験片を切り出し、その中央部で180°密着曲げ
を行い、該曲げ部の表面状態を観察し、割れ、し
わの発生がなく平滑なものを曲げ加工性が良いと
いうことで○印、割れが明らかに発生しているも
のを曲げ加工性を不良ということで×印、その中
間で割れ、しわがわずかに発生しているものを△
印で表わした。
導電率および引張り強さの測定はJIS−H0505
およびJIS−Z2241に基づいて行つた。
メツキ密着性は上記板の鈍し材についてリード
フレームのメツキ工程と同様にアルカリ脱脂（１
分間）−20％硝酸エツチング（30秒）−450℃加熱
（５分間）−550℃加熱（５分間）を行い、550℃、
５分間加熱で全く膨れの見られないものを○印、
450℃、５分間加熱では膨れは見られないが550
℃、５分間加熱で膨れが発生するものを△印、
450℃、５分間加熱ですでに膨れが発生したもの
を×印で示した。
半田付性は垂直式浸漬法により230℃のSn−40
％Pb共晶半田浴に10秒間浸漬したものの表面を
観察し、その結果表面が滑らかなものを○印、表
面に少し凹凸が見えるものを△印、表面に凹凸が
生じ半田が濡れていない部分を生じているものを
×印で示した。
耐熱性は前記圧延材によりJIS−Z2201に規定
する引張り試験を切り出し、これをアルゴン雰囲
気中で400℃、５分間加熱焼鈍した後、引張り試
験を行い、その引張り強さを焼鈍前と比較し、強
度の低下率が30％以下のものを耐熱性良好として
○印、30％を越えるものを耐熱性不良として×印
で表わした。
The alloy of the present invention relates to a copper alloy for lead frames of devices such as ICs and LSIs that use semiconductors as an element, and particularly relates to a copper alloy that has excellent heat resistance, bending workability, and plating adhesion. In general, devices such as ICs and LSIs that use semiconductors as elements are constructed with semiconductor pellet leads and bonding wires and are hermetically sealed.
It is sealed using ceramic seal technology, and various types are used. Conventionally, the lead frame material for these devices was Kovar (Fe-Nickel), which is an iron-nickel material.
29%Ni-17%Co alloy), 42 alloy, cladding material of Kovar coated with gold, cladding material of iron-nickel alloy coated with Al, phosphor bronze as copper alloy,
C19400 (Cu-Fe-Zn-P alloy), 19500 (Cu-Fe
-Co-Sn-P alloy), C14410 (Cu-Sn-P alloy)
etc. are used. However, although the iron-nickel materials mentioned above have excellent heat resistance and strength, they are expensive, have poor conductivity, and have poor workability, so recently they have become cheaper and have good workability, plating adhesion, and solderability. Copper-based alloys are becoming mainstream. However, the copper alloys mentioned above are heat resistant,
Due to its poor electrical (thermal) properties, bending workability, etc., it was unable to exhibit sufficient properties as a lead frame material. Particularly in recent years, where high density and high degree of integration are strongly required, materials with high conductivity, strength, bendability, heat resistance, and surface quality that can be easily plated have become necessary. . In other words, high reliability, economic efficiency,
Thermal performance is a requirement for current lead frame materials. Surface quality that is easily plated refers to the surface quality that is used to improve the connectivity between semiconductor pellets and lead frames, as well as between bonding wires and lead frames, and to improve and maintain the oxidation resistance, corrosion resistance, solderability, etc. of lead frames. , silver, nickel, tin, etc., have excellent plating adhesion, and such plating processing accounts for a large proportion of the processing cost for materials such as lead frames, and greatly affects quality reliability. Iron-nickel materials such as Kovar and 42 alloy not only have poor electrical conductivity and thermal conductivity, but also are difficult to plate and require special techniques. For example, after sequentially depositing a nickel layer and a Sn-Ni alloy layer on the surface of these base materials, a silver layer is deposited on the Sn-Ni alloy layer, or silver and copper are deposited on the surface of the base material. The surface is plated using a cyan alkaline plating solution containing the following: Generally, there is a strong demand for materials that satisfy the following six items as copper alloys for lead frame materials. (1) Good electrical and thermal conductivity (2) Good heat resistance (3) Good bending workability (4) High strength (5) Good plating adhesion (6) Solderability In view of this, as a result of various research, the present invention has developed a copper alloy for lead frames of semiconductor devices that has better heat resistance and bending workability than conventional copper alloys for lead frames, and has sufficient strength and plating adhesion. With what I did
Ni0.4~4.0wt% (hereinafter abbreviated as %) Sn0.5~5.0%,
It relates to an alloy containing 0.4 to 4.0% Al, 0.3% or less P, and the balance being Cu. That is, the alloy of the present invention uses Cu as a base material and adds Ni, Sn, Al, and P.
The aim is to have a deoxidizing effect by precipitating intermetallic compounds such as NixSny, NixAly, NixPy, and SnxPy as minute precipitates and by adding P. Furthermore, Ni, Sn, and Al are solidified in the Cu base. This is a copper alloy for lead frames that aims to strengthen the base material by melting, and has strength and heat resistance that exceed conventional wisdom as a copper alloy, as well as good plating adhesion and solderability. It is. Therefore, in the alloy of the present invention, Ni0.4 to 4.0%,
The reason why we limited it to Sn0.5~5.0%Al0.4~4.0%, P0.3% or less is that if it is less than Ni0.4%, Sn0.5%Al0.4%, the required strength and heat resistance cannot be obtained. , Ni4.0%,
Exceeding 5.0% Sn, 4.0% Al, and 0.3% P will provide excellent performance in terms of strength and heat resistance, but will not only deteriorate bending workability but also deteriorate plating adhesion and solderability. be. The alloy of the present invention will be explained below using examples. After melting Cu using a graphite crucible and covering the hot water surface with charcoal powder, Ni, Sn,
Al and P were added in this order and this was cast to obtain an ingot with a width of 150 mm, a length of 200 mm, and a thickness of 25 mm as shown in Table 1. Next, the surface of this ingot was chamfered by 2.5 mm per side. After hot rolling, a plate with a width of 150 mm and a thickness of 8 mm was repeatedly cold rolled and annealed to achieve a final rolling rate of 40%.
A cold-rolled material with a thickness of 0.3 mm was obtained. The bending workability, electrical conductivity, tensile strength, heat resistance, plating adhesion, and solderability of these plates were measured. These results are shown in Table 1. For comparison, similar measurements were performed on conventional lead frame alloys, and the results are also listed in Table 1. For bending workability, cut a rectangular specimen 5 mm wide and 50 mm long from the plate material, bend it 180° closely at the center, observe the surface condition of the bent part, and check whether it is smooth and free of cracks or wrinkles. Items with good bending workability are marked with ○, items with obvious cracks are marked with poor bending workability, and items with cracks or wrinkles in the middle are marked with △.
Represented by a mark. Measurement of conductivity and tensile strength is based on JIS-H0505
and JIS-Z2241. The plating adhesion was determined by alkaline degreasing (1
- 20% nitric acid etching (30 seconds) - heating at 450°C (5 minutes) - heating at 550°C (5 minutes);
Items that show no swelling after heating for 5 minutes are marked with a circle.
No swelling was observed when heated at 450℃ for 5 minutes, but the temperature was 550℃.
Items that bulge after heating at ℃ for 5 minutes are marked with △.
Items that had already blistered after heating at 450°C for 5 minutes were marked with an x. Solderability of Sn-40 at 230°C was determined by vertical dipping method.
Observe the surface of the product immersed in the %Pb eutectic solder bath for 10 seconds. As a result, those with smooth surfaces are marked with ○, those with slight irregularities on the surface are marked with △, and areas with uneven surfaces and no solder wet. Those in which this occurred are marked with an x. Heat resistance was determined by cutting out the tensile test specified in JIS-Z2201 using the rolled material, annealing it at 400°C for 5 minutes in an argon atmosphere, performing a tensile test, and comparing the tensile strength with that before annealing. A case where the rate of decrease in strength was 30% or less was considered to have good heat resistance and was marked with an ○, and a case where the reduction rate exceeded 30% was judged to have poor heat resistance and was marked with an x.
【表】【table】
【表】
第１表から明らかな如く本発明合金No.１〜14は
導電率12〜61％IACS、引張り強さ56〜75Kgｆ／
mm2の特性を示し、良好な曲げ加工性と耐熱性を有
しており、Cu−Fe−Zn−Ｐ合金に匹敵する導電
率とはるかに優れた引張り強度、耐熱性を有して
いることがわかる。他にメツキ密着性、半田付性
もCu−Zn−Ｐ合金に比べ十分優れていることが
わかる。
これに対してNiの少ない比較合金No.21は引張
り強度および耐熱性が十分でなく曲げ加工性も若
干劣り、Niの多い比較合金No.25は導電率が低い
ばかりでなく、曲げ加工性も悪く、メツキ密着性
および半田付性も劣つている。Snの少ない比較
合金No.20は引張り強度および耐熱性が十分でな
く、曲げ加工性も若干劣り、Snの多い比較合金
No.26は導電率が低いばかりでなく、曲げ加工性も
悪く、メツキ密着性および半田付性も劣つてい
る。Alの少ない比較合金No.19は引張り強度およ
び耐熱性が十分でなく、曲げ加工性も若干劣り、
Alの多い比較合金No.27は導電率が低いばかりで
なく、曲げ加工性も悪く、メツキ密着性および半
田付性も劣つている。Ｐの多い比較合金No.15はメ
ツキ密着性および半田付性が劣つている。Niと
Snの少ない比較合金No.18は引張り強度および耐
熱性が十分でない。
NiとSnの多い比較合金No.22は導電率が低いば
かりでなく、曲げ加工性も悪く、メツキ密着性お
よび半田付性も劣つている。NiとAlの少ない比
較合金No.17は引張り強度および耐熱性が十分でな
い。NiとAlの多い比較合金No.23は導電率が低い
ばかりでなく、曲げ加工性も悪く、メツキ密着性
および半田付性も劣つている。SnとAlの少ない
比較合金No.16は引張り強度および耐熱性が十分で
ない。SnとAlの多い比較合金No.24は導電率が低
いばかりでなく、曲げ加工性も悪く、メツキ密着
性および半田付性も劣つている。
以上詳述したように本発明合金は優れた強度、
耐熱性と曲げ加工性をあわせ持ち、メツキ密着
性、半田付性も良好な銅合金であり、半導体機器
のリードフレーム材として顕著な効果を奏するも
のである。[Table] As is clear from Table 1, the present invention alloys No. 1 to 14 have a conductivity of 12 to 61% IACS and a tensile strength of 56 to 75 Kgf/
mm 2 and has good bending workability and heat resistance, and has electrical conductivity comparable to Cu-Fe-Zn-P alloy and far superior tensile strength and heat resistance. I understand. It can also be seen that the plating adhesion and solderability are also sufficiently superior to that of the Cu-Zn-P alloy. On the other hand, comparative alloy No. 21, which contains less Ni, has insufficient tensile strength and heat resistance, and is slightly inferior in bending workability, and comparative alloy No. 25, which contains more Ni, not only has low conductivity but also poor bending workability. Moreover, the plating adhesion and soldering properties are also poor. Comparative alloy No. 20 with less Sn did not have sufficient tensile strength and heat resistance, and its bending workability was also slightly inferior.
No. 26 not only has low conductivity, but also poor bending workability, poor plating adhesion, and poor solderability. Comparative alloy No. 19 with low Al content did not have sufficient tensile strength and heat resistance, and its bending workability was also slightly inferior.
Comparative alloy No. 27, which contains a large amount of Al, not only has low conductivity, but also poor bending workability, and poor plating adhesion and solderability. Comparative alloy No. 15, which contains a large amount of P, has poor plating adhesion and solderability. Ni and
Comparative alloy No. 18 with low Sn content does not have sufficient tensile strength and heat resistance. Comparative alloy No. 22, which contains a large amount of Ni and Sn, not only has low conductivity, but also poor bending workability, and poor plating adhesion and solderability. Comparative alloy No. 17, which contains less Ni and Al, has insufficient tensile strength and heat resistance. Comparative alloy No. 23, which contains a large amount of Ni and Al, not only has low conductivity, but also poor bending workability, and poor plating adhesion and solderability. Comparative alloy No. 16, which contains less Sn and Al, has insufficient tensile strength and heat resistance. Comparative alloy No. 24, which contains a large amount of Sn and Al, not only has low conductivity, but also poor bending workability, and poor plating adhesion and solderability. As detailed above, the alloy of the present invention has excellent strength and
It is a copper alloy that has both heat resistance and bending workability, and also has good plating adhesion and solderability, and is a remarkable material for lead frames of semiconductor devices.