JPH07115280A - Multilayer printed wiring board and its manufacture - Google Patents

Abstract

PURPOSE:To enhance printing characteristics of solder resist in an undercut part between a metal foil surface of conductive circuit patterns of an outermost layer of a multilayer printed wiring board and a surface of a board material, washing characteristics of flux, etc., and mounting characteristics of chip components. CONSTITUTION:In a multilayer printed wiring board and its manufacturing method, the board is formed by a step that an intermediate connector 23 and both-sided printed wiring boards 21, 22 are respectively alternately arranged so that the separately made intermediate connector 23 is positioned between the both-sided printed wiring boards 21, 22 according to the number of layer, and compressed by heating pressure and laminated. There is no step difference between a metal foil surface of conductive circuit patterns 24 of the outermost layer and a surface of a board material of the outermost layer to form a smooth surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board used in electronic equipment, in which a metal foil is used as a conductor circuit pattern of inner and outer layers of a substrate material, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, electronic devices have become lighter, thinner, shorter, and smaller, and accordingly, high-speed and high-density component mounting has been required for printed wiring boards. Is rapidly moving to surface mounting. In the conventional printed wiring board, the method for electrical connection between layers is generally through-hole plating.

A conventional method for manufacturing a printed wiring board will be described by taking a four-layer printed wiring board as an example.

FIGS. 3 (a) to 3 (e) are process sectional views of a conventional multilayer printed wiring board, and a four-layer printed wiring board is taken as an example. First, the inner layer conductor circuit pattern 31 is formed by selectively etching the copper foil on the surface of the insulating substrate of the glass cloth substrate material epoxy resin copper clad laminate having the copper foil adhered to both sides. As a result, the double-sided printed wiring board 34 is manufactured. Next, the inner layer copper foil is subjected to a surface treatment, sandwiched between the outermost layer copper foil 32 and the insulating substrate 33, adhered by heating and pressing, and laminated in a shape as shown in FIG. 3B. Next, as shown in FIG. 3 (c), a drill hole is drilled to form a through hole 35, the surface of the copper foil is leveled and the inner wall of the hole is cleaned, and then a copper plating method is performed as shown in FIG. 3 (d). Thus, the electrode layer 36 is provided in the through hole 45. In this way, electrical connection between layers is achieved. Next, as shown in FIG. 3E, the through holes are filled up, and the outermost layer copper foil is selectively plated and etched to form the outermost layer conductor circuit pattern 37. Then, the solder resist / symbol printing is performed, the outer shape is processed, and the flux is applied to obtain a four-layer printed wiring board. After that, the leaded component and the chip component are mounted and soldered, and the flux is cleaned and incorporated into the product.

[0005]

However, the above conventional configuration has the following problems. In the conventional configuration, as shown in FIG. 3 (e), the substrate material surface and the pattern surface after the formation of the conductor circuit pattern on the substrate surface, the substrate material, the copper foil, and the copper-plated portion formed on the surface of the copper foil. Since a step can be formed at, there are the following problems at present when high-density mounting is required. First, in the solder resist printing step, the solder resist is hard to be printed on the step portion between the surface of the substrate material and the metal foil surface of the conductor circuit pattern, and heat resistance, chemical resistance, and insulation may deteriorate. Secondly, there is a risk that the parts will tilt due to the stepped portion when the chip parts are surface-mounted, resulting in defective soldering. Third, the metal foil on the surface of the board material and the conductor circuit pattern after cleaning in the flux cleaning process. The problem is that flux and thermal decomposition products at the time of soldering the flux may remain on the stepped portion of the surface, causing insulation deterioration, corrosion, disconnection, and the like.

[0006]

The present invention is to solve the above problems. As a means, a releasable protective film is adhered to the organic composite substrate material having compressibility by heating and pressurizing, a through hole is provided in the organic composite substrate material provided with the releasable protective film, and the through hole is provided. After filling the conductive paste for electrical connection between the layers, the intermediate connecting body from which the releasable protective film is peeled from the organic composite substrate material, and a metal foil is stuck to the surface thereof and bonded by heating and pressing. , A double-sided printed wiring board having a step of forming a conductor circuit pattern is alternately arranged so that a separately prepared intermediate connector is located between the double-sided printed wiring boards according to the number of layers, and compressed by heating and pressing. , The metal foil of the conductor circuit pattern of the outermost layer is embedded in the organic composite substrate material by the thickness thereof, and the surface of the substrate material and the metal of the conductor circuit pattern are formed in the outermost layer. Attempt to resolve the problem by making the surface smooth surface without steps.

[0007]

In the multilayer printed wiring board of the present invention, an organic composite substrate material having a compressibility is used as the substrate material, and the outermost layer of the metal foil of the conductor circuit pattern is made of an organic material by an amount corresponding to the thickness of the organic foil by applying heat and pressure by a hot press. By embedding in the composite board material, the surface of the board material of the outermost layer and the metal foil surface of the conductor circuit pattern have a smooth surface with no step, and the step between the conductor circuit pattern and the board material of the outermost layer of the conventional multilayer printed wiring board is formed. It is possible to improve the printability of the solder resist in the part, the cleaning properties of flux and the like and the mountability of chip parts.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a multilayer printed wiring board according to an embodiment of the present invention will be described below with reference to the drawings using a four-layer board as an example.

FIGS. 1 and 2 show a fourth embodiment of the present invention.
It is a process cross-sectional view showing a method for manufacturing a layer printed wiring board,
1A to 1H show the steps of forming the first and second double-sided printed wiring boards, FIGS. 1A to 1E show the step of forming an intermediate connector, and FIG. (a) and (b) show the steps of forming a multilayer printed wiring board by laminating an intermediate connector between the first double-sided printed wiring board and the second double-sided printed wiring board. The feature is that the metal foil of the conductor circuit pattern of the outermost layer is embedded in the substrate material by the thickness by heating and pressing with a hot press, and the surface of the outermost substrate material and the metal foil surface of the conductor circuit pattern are smooth without any step. It can be mentioned as an aspect.

As the organic composite substrate material, a composite substrate material obtained by impregnating an aromatic polyamide fiber with a thermosetting epoxy resin has a thickness of 150 to 220 μm and a porosity of 10 to 6.
0% aramid-epoxy sheet was used. A polyethylene terephthalate film having a thickness of 4 to 50 μm was used as a releasable protective film laminated on both sides of the organic composite substrate material. As the conductive paste, at least one kind of silver and copper was used as the metal particles, and those dispersed in a solventless epoxy resin and a curing agent were used. Metal foil roughens one side and both sides of electrolytic copper foil,
The one having a thickness of 35 μm was used.

First, as shown in FIG. 1 (a), an aramid-epoxy sheet 12 having a thickness t1 and provided with a releasable protective film 11 on both sides is prepared. 16 is a hole existing inside the aramid-epoxy sheet 12. Using a hot press, this is pressed at a temperature of 100 to 110 ° C. and a pressure of 20 to 3
Precompress the aramid-epoxy sheet 12 by hot pressing at 0 kg / cm2 for 3-5 minutes. At this time, the aramid-epoxy sheet 12 is compressed as shown in FIG. 1 (b), the thickness t2 becomes 110 to 160 .mu.m, the porosity becomes 10 to 30%, and the shape of the holes 16 becomes small. The purpose of this precompression is to reduce the porosity, reduce the shape of the pores 16, and to bring the releasable protective film 11 and the aramid-epoxy sheet 12 into close contact with each other. -Epoxy sheet 12 and copper foil 15
It is to prevent the conductive paste 14 from entering the interface with and to control the amount of the binder in the conductive paste 14 permeating to the aramid-epoxy sheet 12 side. Next, as shown in FIG. 1C, a through hole 13 having a diameter of 70 to 200 μm was formed by drilling, carbon dioxide gas, and excimer laser processing. The through-hole 13 is filled with the conductive paste 14 produced as described above. As a method of filling the conductive paste 14, the aramid-epoxy sheet 12 in which the through holes 13 are formed is placed on a table (not shown) of a printing machine, and the aramid-epoxy sheet 12 is placed.
The conductive paste 14 is directly printed on the releasable protective film 11 by using a squeegee while sucking from the back surface. At this time, the releasable protective film 11 on the upper surface plays a role of a printing mask and a role of preventing contamination of the surface of the aramid-epoxy sheet 12. Conductive paste 14
After printing the releasable protective film 11,
The intermediate connector of (e) is manufactured. Next, a copper foil 15 is roughened on both sides of the intermediate connection body on the surface on which the conductor circuit pattern of the inner layer is formed, and on the surface on which the conductor circuit pattern of the outermost layer is formed, is roughened on one side or roughened on both sides. The roughened surfaces of the copper foil are laminated and combined in a shape as shown in FIG. Using a vacuum hot press, this is pressed at a temperature of 200 to 210 ° C.,
The double-sided roughened copper foil is adhered to the aramid-epoxy sheet 12 by applying heat and pressure at a pressure of 50-60 kg / cm 2 for 60 minutes. In this step, the conductive paste 14 and the aramid-epoxy sheet 12 are compressed, but at that time, the binder component is extruded from between the conductive materials, and the conductive materials and the bonding between the conductive material and the copper foil are strengthened and the interlayer is formed. The electrical connection of is stable. Moreover, as shown in FIG.
After being bonded to the aramid-epoxy sheet 12 has a thickness t4 of 90 to 110 .mu.m, a porosity of 0 to 5%, and the shape of the holes 16 is further reduced. Next in FIG.
As shown in (h), the conductor circuit pattern 17 is formed by etching. In this way, the first double-sided printed wiring board is formed. A second double-sided printed wiring board having another conductor circuit pattern is formed by the same process. The first and second double-sided printed wiring boards can be used as double-sided printed wiring boards in this state.

Next, the step of laminating the four-layer board with the first and second double-sided printed wiring boards using the intermediate connector will be described. First, as shown in FIG. 2A, the surfaces of the first double-sided printed wiring board 21 and the second double-sided printed wiring board 22 on which the inner layer conductor circuit patterns 25 are formed are set to the inner side, and the intermediate connector 23 is sandwiched therebetween. . Next, as shown in FIG. 2B, the first double-sided printed wiring board 21, the intermediate connector 23, and the second double-sided printed wiring board 22 are bonded by heating and pressing under the same lamination conditions as described above. Stack. At this time, the conductor circuit patterns of the first and second double-sided printed wiring boards are electrically connected by the conductive paste of the intermediate connector 23. In this step, by embedding the copper foil 15 of the outermost conductor circuit pattern 24 in the aramid-epoxy sheet 12 by the thickness t3, the surface of the outermost aramid-epoxy sheet 12 and the outermost conductor circuit pattern 24 are formed. The metal foil surface has a smooth surface with no steps, improving the printability of the solder resist on the outermost conductor circuit pattern of the conventional multilayer printed wiring board and the step portion of the board material, the cleaning performance of the flux and the mountability of chip parts. Can be enabled.

In order to manufacture a multilayer printed wiring board having a large number of laminated layers, a required number of inner and outermost conductor circuit patterns are formed on a double-sided printed wiring board and a plurality of interconnecting layers are formed. It is also possible to prepare an intermediate connecting body, insert the intermediate connecting body between the respective double-sided printed wiring boards, and then heat and pressurize it with a vacuum heat press to laminate them at once. Needless to say, it is also effective to repeat the steps of FIGS. 2A and 2B to stack the intermediate connector and the double-sided printed wiring board one by one and heat and pressurize them.

[0014]

As described above, in the multilayer printed wiring board of the present invention, an organic composite substrate material having compressibility is used as the substrate material, and the outermost layer of the metal foil of the conductor circuit pattern is heated and pressed by a hot press. By embedding the same thickness as that in the organic composite board material, the surface of the board material of the outermost layer and the metal foil surface of the conductor circuit pattern have a smooth surface without steps, and the conductor circuit of the outermost layer of the conventional multilayer printed wiring board is obtained. It is possible to improve the printability of the solder resist in the step portion between the pattern and the substrate material, the cleaning performance of the flux and the like, and the mountability of the chip component.

[Brief description of drawings]

FIG. 1 is a process sectional view showing a method for manufacturing a double-sided printed wiring board used for a multilayer printed wiring board according to an embodiment of the present invention.

FIG. 2 is a process sectional view showing a method for manufacturing a multilayer printed wiring board according to an example of the present invention.

FIG. 3 is a process cross-sectional view showing a conventional method for manufacturing a multilayer printed wiring board.

[Explanation of symbols]

11 Releasable Protective Film 12 Aramid-Epoxy Sheet (Organic Composite Substrate Material) 13 Through Hole 14 Conductive Paste 15 Copper Foil (Metal Foil) 16 Hole 17 Conductor Circuit Pattern 21 First Double-sided Printed Wiring Board 22 Second Double-sided printed wiring board 23 Intermediate connector 24 Outermost layer conductor circuit pattern 25 Inner layer conductor circuit pattern

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Nakatani 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. An organic composite substrate material is used as a substrate material, a conductor circuit pattern of inner and outer layers is formed of a metal foil, and a plurality of conductive pastes filled in a through hole provided in the organic composite substrate material are used. The multilayer printed wiring board is characterized in that the metal foil surface of the conductor circuit pattern of the outermost layer and the surface of the substrate material of the outermost layer are smooth surfaces having no steps for electrical connection between the layers. 2. The multilayer printed wiring board according to claim 1, wherein the organic composite substrate material is a composite material of aromatic polyamide fiber and thermosetting resin. 3. The multilayer printed wiring board according to claim 1, wherein the organic composite substrate material is aramid-epoxy sheet. 4. The method for producing a multilayer printed wiring board according to claim 1, wherein the metal foil is formed of rolled copper or electrolytic copper and has a thickness of 18 to 70 μm. 5. The metal foil is roughened by surface treatment on both sides or one side of the metal foil.
The multilayer printed wiring board described. 6. A releasable protective film is adhered to an organic composite substrate material having compressibility by heating and pressing, and a through hole is provided in the organic composite substrate material provided with the releasable protective film, and the through hole is formed. After filling a hole with a conductive paste for achieving an electrical connection between layers, an intermediate connector having the release protective film peeled from the organic composite substrate material,
Further, a double-sided printed wiring board having a step of forming a conductor circuit pattern by laminating a metal foil on the surface and adhering by heating and pressurization is arranged such that an intermediate connector separately prepared is positioned between the double-sided printed wiring boards according to the number of layers. Are formed by a process of alternately arranging them on each other, compressing by heating and pressurizing and laminating, and there is no step between the surface of the metal foil of the conductor circuit pattern of the outermost layer and the surface of the substrate material of the outermost layer. A method for manufacturing a multilayer printed wiring board, which is characterized by having a smooth surface. 7. The method for producing a multilayer printed wiring board according to claim 6, wherein the compressibility of the organic composite substrate material by heating and pressing is 20 to 40%. 8. The method for producing a multilayer printed wiring board according to claim 6, wherein the organic composite substrate material is a composite material of aromatic polyamide fiber and thermosetting resin. 9. The method for producing a multilayer printed wiring board according to claim 6, wherein the organic composite substrate material is aramid-epoxy sheet. 10. The method for producing a multilayer printed wiring board according to claim 6, wherein the metal foil is formed of rolled copper or electrolytic copper and has a thickness of 18 to 70 μm. 11. The method for producing a multilayer printed wiring board according to claim 6, wherein the metal foil has its surface on both sides or one side roughened by surface treatment.