JPH10145044A - Multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the mounting density and wiring pattern density in a high soldering heat-resistive environment by providing continuity connection holes in land layer regions for soldering electrodes of flat mounting components and charging a high thermal conductivity and heat-resistive thermosetting resin in the connection holes. SOLUTION: On the front and back sides of a laminate substrate 1 outer and inner conductors 2, 3 are formed and laminate 1 is laid to form a printed multilayer wiring board 19. Through-holes 4 are formed through this board 19 and a uniform Cu plating layer 5 is formed on the inner walls 4a of the holes 4 and front and back sides of the outer and dinner layers conductors 2, 3 to form continuity connection holes 9 in which a high-thermal conductive resin paste 16 is then charged and pre-dried and undesired paste 16 on the tops of the connection holes 9 is planarized and removed, it is hardened. On the connection holes 9, flat mounting components 15 are mounted by high temp. soldering. This reduces the connection hole land regions 18 and raises the mounting density and wiring density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a double-sided or multilayer printed wiring board on which surface-mounted components can be mounted at a high density.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and high-density mounting of electronic components, progress has been made further so that surface-mounted components can be mounted at even higher densities. Hereinafter, FIGS.
The manufacturing process of the printed wiring board 39 according to the prior art will be described with reference to (b), FIGS. 6 (c) to (e), and FIGS. 7 (f) to (g).

[0003] First, using a laminated substrate 21 having two or more wiring layers, using a laminated glass epoxy resin multilayer printed wiring board 39 with the laminated substrate 21 laminated on an outer conductor 22 (FIG. 1A). The through holes 24 are selectively formed in the multilayer printed wiring board 39 (FIG. 2B).

Next, the inner wall 24A of the through hole 24 and the inner conductor layer 2 are formed by a combined method of chemical plating and electroplating.
The first copper layer 25 is formed on the entire surface of the front and back layers of the third and outer conductor layers 22 to form the conductive connection holes 32 (FIG. 3C). Next, a thermosetting resin (epoxy) 26 is filled into the holes of the conductive connection holes 32 and heat-cured to smooth the surface of the first copper layer 25 (d)
Figure). Next, a second copper layer 27 is formed by electroplating (FIG. 5E).

Next, a known photosensitive dry film (photosensitive layer thickness: 50 μm) 37 is laminated on the surface of the second copper layer 27, and a negative mask 2 for a wiring pattern is formed on the surface.
Then, UV exposure 29 is performed using FIG. 8 (f figure). Further, the unnecessary portions of the copper plating layers 25 and 27 and the outer conductor layer 22 are removed by an alkali developing and etching process, and the formation of the through-hole lands 33 and 34 and the conductor patterns 30 and 31 in a desired wide area 38 can be obtained ( g figure).

[0008] As shown in FIG. 8, when the through holes lands 33, 34 in the wide area 38 and the surface mount component 15 are soldered (reflow furnace), the thermosetting resin 2 in the holes of the conductive connection holes 32 is soldered.
6, the thermal expansion swelling 36 of the resin 26 occurs due to the heat resistance of the solder, the swelling 35 of the second through-hole land layer occurs, and the electrical connection reliability of the surface mount component 15 and the multilayer printed wiring board 3
A problem may arise in utilizing the mounting area of No. 9 effectively. Further, the above manufacturing technique (through-hole land configuration) is described in Japanese Patent Publication No. 8-31695.

[0007]

However, according to the above-mentioned technology, the following problems have been solved in that the solderability of the reflow furnace for high-density mounting and the mounting area of the multilayer printed wiring board 39 for higher density are more effectively utilized. Have such issues.

First, as shown in FIG. 8, in a recent reflow furnace soldering environment, the solder melting temperature is set to a high temperature condition, and the thermosetting resin 2 formed in the conductive connection hole 32 is formed.
6. For example, the epoxy resin 26 undergoes thermal expansion and swelling (170 ° C., transition temperature) 36 due to high-temperature soldering heat resistance, causing a swelling 35 phenomenon of the second through-hole land layer. Connection reliability is problematic.

Second, the through-hole land layers 33, 34 for the surface mount component 15 are formed of a wide area 38, and the land layers 33, 34 are also formed to have a large thickness of 50 to 55 μm. Therefore, the multilayer printed wiring board 39
This makes effective use of the mounting area, and causes a problem in the development of high-density mounting. In addition, since the land layers 33 and 34 are thick, a known side etching amount becomes large, and there is a problem that it is difficult to form a known landless.

Accordingly, the present invention solves the above-mentioned problems and provides a multilayer printed wiring board 1 capable of high-density mounting and high-density wiring patterns 11 in an environment of high-temperature soldering heat resistance.
9 is intended to be provided.

[0011]

According to the present invention, in order to achieve the above-mentioned object, a conductive connection hole 9 for conducting to the front and back surfaces of a multilayer printed wiring board 19 or the inner layer conductor 3 is provided.
Is provided in a land layer 8 region for soldering the electrode portion 14 of

A conductive resin paste 1 comprising a metal powder 10 in a heat-resistant thermosetting resin 12 having a large heat conductor.
6, a high-density mounting multilayer printed wiring board 19 capable of being formed by filling the hole of the conductive connection hole 9 and soldering the surface mounting component 15 onto the hole 9.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a conductive resin paste 16 comprising a heat-resistant polyimide resin HI-L12 and a conductive metal powder 10 is used to form a conductive connection hole 9 in a hole. And the conductive connection hole 9
The surface mount component 15 can be easily mounted and soldered on the hole of
Further, since the land layer 8 can be formed only of the first copper layer 5, the wiring density can be further increased to realize a higher density mounting.

[0014]

2A and 2B showing an embodiment of the present invention.
This will be specifically described based on FIGS. 3C to 3E and 4F.

[0015]

Embodiment 1 First, FIG. 2A shows a laminated substrate 1 having wiring layers 2 and 3 on both sides or more.
The outermost layer of the outermost layer is formed of the outer layer conductor 2 and has a thickness of about 1.6 mm. And the like.

Next, as shown in FIG.
Using a 0.6 mm drill, the through hole 4 is selectively drilled (Hitachi high precision drilling machine. MARK100). Examples of the method of forming the hole include known methods such as drilling, plasma, laser processing, and press.

Next, as shown in FIG. 3 (c), a copper plating layer 5 having a uniform film thickness of 20 to 25 μm is formed on the inner wall 4A of the through hole 4, the inner conductor 3 and the outer conductor 2 on the front and back surfaces. And conductive connection holes 9 (hereinafter referred to as through holes). Known examples of the copper plating method include an electroless plating method, a combined use method of electroless plating and electroplating, a plasma method, and a thermal melting method.

Next, as shown in FIG. 3D, the conductive resin paste 16 of the present invention (about 84 wt% of copper powder having a particle size of 4 to 11 μm and the remainder is heat-resistant polyimide resin 12 Made by Hitachi Chemical Co., Ltd. Product name: HI-
L) is selectively filled using a squeegee, the conductive resin paste 16 is temporarily dried at about 80 ° C., and the unnecessary conductive resin paste 16 above the through holes 9 is flattened and removed by a polishing machine. And in a drying oven at 170 ° C. The heat-resistant polyimide resin (HI-L) 12 has the following features.

Hereinafter, the first, second and third aspects will be described. First, it is soluble in low-boiling solvents. That is, HI-L is soluble in low-boiling solvents such as acetone and methyl ethyl ketone. For this reason, since the range of the drying temperature at the time of coating and filling production is widened, the degree of reaction can be easily controlled, and the same operation as the epoxy resin can be performed.

Second, the curability is excellent.
That is, HI-L12 is 170
The resin 12 is cured at 60 ° C. for 60 minutes, and the transition temperature of the cured resin 12 of the present invention is about 320 ° C. Therefore, the solder heat resistance is about 26.
Under an environment of passing through a reflow furnace three times at 0 ° C., the resin swelling 36 in the through holes 9 does not occur. Third, thermal conductor (10 ^-4 cal / sec)
5.2 to 5.8.

Further, as shown in FIG. 3E, a known photosensitive dry film 17 (manufactured by Hitachi Chemical Co., Ltd., trade name: N-24 (40 μm)) is laminated, and UV exposure is performed using a negative mask 6. Perform 7

Thereafter, as shown in FIG. 4 (f), the phenomenon is carried out with anhydrous sodium carbonate (1 wt% -Na2CO3 aqueous solution), and then, etching stripping (2.5-3. (Aqueous sodium hydroxide solution of 0 wt%), the through-hole land area 18 is small, and a desired multilayer printed wiring board 19 for heat resistance to soldering is obtained.

As shown in FIG. 1, this is an embodiment of the present invention.
FIG. 5 is a cross-sectional view of the multilayer printed wiring board 19 after soldering No. 5, and using a high heat-resistant conductive paste 16, the surface mount component 15 can be soldered at a high temperature on the through-hole 9;
In addition, the area can be effectively used for mounting the multilayer printed wiring board 19.

[0024]

As described above, according to the present invention,
By using the heat-resistant polyimide resin conductive paste 16, soldering can be performed in a high-temperature environment, and the mounting area can be effectively utilized. Therefore, the following specific effects can be obtained.

(1) According to the present invention, the surface-mounted component 1 is formed by using the highly heat-resistant conductive paste 16 of the present invention.
5 solder through-hole land 8 is the first copper plating layer 5
It is possible to invent a multi-layer printed wiring board 19 which can be formed with only the through-hole 9 and can be soldered on the through-hole 9 so that the through-hole land area 18 can be reduced and high-density mounting and high-density wiring can be realized. The effect contributing above is extremely large.

(2) According to the present invention, the heat-resistant polyimide resin HI-L12 is used to fill the through holes 9 with
Because of this, when soldering the surface mount component 15 (when passing through a reflow furnace), the swelling 36 of the filling resin 12 in the through-hole 9 does not occur, so that the electrical connection reliability of the electrode portion 14 is improved. Can be secured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state in which a surface mount component is mounted on a multilayer printed wiring board according to the present invention.

FIGS. 2A and 2B are cross-sectional views illustrating a manufacturing process of the present invention.

FIGS. 3 (c) to 3 (e) are cross-sectional views illustrating a manufacturing process of the present invention.

FIG. 4 (f) is a sectional view showing a manufacturing step of the present invention.

FIGS. 5A and 5B are cross-sectional views showing a conventional manufacturing process.

FIGS. 6C to 6E are cross-sectional views showing a conventional manufacturing process.

FIGS. 7F to 7G are cross-sectional views showing a conventional manufacturing process.

FIG. 8 is a sectional view showing a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laminated board 2 ... Outer layer conductor (wiring layer) 3 ... Interior conductor (wiring layer) 4 ... Through-hole 4A ... Hole inner wall 5 ... 1st copper plating layer 6 ...
Mask (negative) 7 UV exposure 8 Land layer 9 Conducting connection hole 10
Metal powder 11: Conductive pattern 12: Heat-resistant thermosetting resin 13
... Solder 14 ... Electrode part 15 ... Surface mount component 16 ... Conductive resin paste 17 ...
Photosensitive dry film 18 through-hole land area 19 multilayer printed wiring board 21 of the present invention 21 laminated substrate 22 outer conductor layer 23 inner conductor layer 24 through hole 24A inner wall 25 first copper layer 26 Thermosetting resin 27 ... second copper layer 28 ... mask (negative) 29 ... UV exposure 30 ... first conductor pattern 31 ... second conductor pattern 32 ... conduction connection hole 33 ... first through hole land 34 ... second through Hole land 35: swelling of second through-hole layer 36: thermal expansion swelling 37: photosensitive dry film 38: through-hole land area 39: conventional multilayer printed wiring board

[Procedure amendment]

[Submission date] November 29, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015]

Embodiment 1 First, FIG. 2A shows a laminated substrate 1 having wiring layers 2 and 3 on both sides or more.
The outermost layer of the outermost layer is made of an outer layer conductor 2 and has a thickness of about 1.6 mm, for example, a multilayer printed circuit made of an outermost layer copper foil in which a glass base material is impregnated with epoxy resin and bonded in multiple layers.
Known wiring board 19 and the like.

Claims (3)

[Claims] A laminated board (1) having wiring layers (2, 3) on both sides or more is used. The laminated board (1) has a through hole (4) and a copper plating layer (5). In the multilayer printed wiring board (19) having a conductive connection hole (9) and a land layer (8), at least one exposed surface of the conductive connection hole (9) has a solderability. This filler has a large heat conductor and is filled with a heat-resistant thermosetting resin (12). 2. The heat-resistant thermosetting resin (12) according to claim 1, wherein the heat-resistant thermosetting resin (12) is made of a material having conductivity and solderability, and is made of a heat-resistant polyimide resin (12). (19) A multilayer printed wiring board (19) comprising a conductive resin paste (16) containing: 3. The metal powder (10) according to claim 2, wherein
Is composed of at least one metal element selected from the group consisting of silver, nickel and copper.