JPH03280593A - Manufacture of multilayer circuit board - Google Patents

Abstract

PURPOSE:To integrally press-bond a film base material to thick film conductive paste by employing the paste having fluidity equivalent to or larger than that of the material made of thermally deformable polymer resin. CONSTITUTION:Thick film conductive paste containing vinyl chloride-vinyl acetate copolymer as a binder and a predetermined amount of fine silver particles each having 5mum of average particle size is screen printed on a first film base material 11a having 30mum of thickness and made of polycarbonate to form a connecting land 12. After holes 13 are opened at a plurality of second film base materials 11b1-11b3 each having a thermal deforming temperature and made of polycarbonate, the paste is screen printed to form a connecting land 14 on a surface region including the inner surfaces of the holes 13. Them, the first material 11a and the second materials 11b1-11b3 are so sequentially laminated between stationary plates of a hot press that the lands 12, 14 coincide, and then hot pressed by the plates of the press.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method of manufacturing a multilayer circuit board on which electronic components can be mounted with high density.

(Prior art) Recently, various electronic devices have become lighter, thinner, and smaller.
A similar trend toward lighter, thinner, and smaller home appliances is progressing.

The hardware basis for such miniaturization is the miniaturization of semiconductor devices and other electronic components. Among electronic circuit boards, circuit boards based on glass epoxy resin are generally used, but as the trend toward miniaturization requires particularly high-density mounting, multilayer and flexible circuit boards are being used. It can be used in combination with substrates, hybrid ICs, etc.

However, in the technical field of consumer circuit boards, where low cost is strongly required, when a multilayer (class of 4 or more layers) glass epoxy resin base material is used, it is necessary to form through holes by plating, which is a complicated process. requires a process,
Costs will rise significantly. Further, even in flexible circuit boards, many problems remain in increasing the density of circuit boards, such as the need for expensive materials as base materials in consideration of heat resistance and the like.

In order to solve these problems, we developed a simple manufacturing process,
Multilayer plastic circuit boards have been developed that have features such as low cost and three-dimensional wiring.

The manufacturing process of such a multilayer plastic circuit board is the third step.
This will be explained below with reference to Figures (A) and (B).

First, holes 2 are formed in a plurality of (for example, four) film substrates 1a to 1d made of heat-deformable polymer resin, and then a thick film conductive paste using heat-deformable resin as a binder is screen printed. A connecting land 3 is formed in the surface area around the hole 2, and a wiring 4 connected to this land 3 is formed. In addition, in this screen printing process, on the surface corresponding to the land 3 of the adjacent upper layer of the film base material 1a-1e excluding the top layer, it is integrated with the land 3,
A connection land 5 connected via the wiring 4 is formed. Subsequently, the film base materials 1a to 1d are stacked and arranged between the fixed plates 6a and 6b of a heat press machine (Fig. 3 (A).
). Next, by hot pressing the film base materials 1a to 1d using the fixed plates 6a and 6b, the lands 3 provided in the surface area around each of the film base materials 1a to 1d and the holes 2 and the base materials 1a to 1e are separated. By crimping and integrating the lands 5 provided with flat surfaces, a multilayer circuit board 8 in which through-holes 7 for connecting interlayer wiring 4 are formed is manufactured, as shown in FIG. 3(B).

According to this method, unlike the manufacturing method of circuit boards using a normal glass epoxy resin base material, the film base material and the wiring are integrated in one heat press, and through holes are formed to connect the layers. This eliminates the need for a complicated plating process, making it possible to manufacture multilayer circuit boards at low cost.

By the way, the formation of throughholes in the above-mentioned method is achieved by the following action. This will be explained next using as an example the case where through holes are formed between the three and four layer film substrates IC and ld shown in FIG. 3(A). When a film base material made of a heat deformable polymer resin on which a land made of a thick film conductive paste with a heat deformable resin as a binder is formed is hot pressed, the film base material 1c on the lower side and the land 5 are deformed by plastic deformation. It flows and bulges in the holes 2 of the upper film base material 1d. At this time, a land 3 made of a conductive paste formed around the hole 2 of the upper film base 1d is connected to a land 5 made of a conductive base raised from the lower film base 1c, and a third
A through hole 7 as shown in the figure is formed.

In the production of the above-mentioned conventional multilayer circuit board, in the case of a connection between two adjacent layers, it is necessary to form a through hole without disconnection depending on the thickness of the film base material and the hole diameter of the base material in which the connection land is formed. becomes possible. In response to this, there is a demand for manufacturing a multilayer circuit board made of, for example, four layers using the above-mentioned film base material and conductive paste, in which the uppermost layer and the lowermost layer are connected by through-holes that penetrate vertically between the wirings. . However, if such a through-hole is to be formed by the method described above, it is necessary to further increase the deformation of the film base material on the bottom layer side to sufficiently bulge the hole where the land on the top layer side is formed.
The conductive paste constituting the land formed on the surface of the base material on the bottom layer side follows the swelling and cannot be sufficiently deformed. As a result, the land breaks when the film base material swells, making it difficult to form through holes with high cutting properties that penetrate between the multiple layers. In addition, here we have explained the through holes that vertically penetrate between the wiring in the top layer and the bottom layer, but also in the case where the connection is made with through holes that penetrate vertically in the middle layer where a land is formed on the upper surface around the hole in the film base material. , which basically causes the same problem as described above.

For this reason, it is possible to connect multi-layer wiring using through-holes provided in different areas, and as a result, to connect the wiring on the top and bottom layers. As the number of lines increases, the wiring formation area decreases, creating a problem that inhibits the formation of high-density wiring.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and has a structure in which a film base material and a thick film conductive paste are integrally crimped, and disconnections between multiple layers occur. The present invention aims to provide a highly reliable method for manufacturing a multilayer circuit board without through-hole connections.

[Structure of the Invention] (Means for Solving the Problems) The present invention consists of a heat-deformable polymer resin printed with a thick film conductive paste having a heat-deformable resin as a binder on the surface area as a connecting land. The first film base material is made of a heat-deformable polymer resin, and a thick-film conductive paste with a heat-deformable resin as a binder is printed as a connection land on the surface area including the inner surface of the hole drilled in advance. When manufacturing a multilayer circuit board by laminating a plurality of second film base materials and crimping and integrating each land and film base material by heating and pressing to form a through hole that conducts between the upper and lower layers, the conductive paste is used as the conductive paste. This method of manufacturing a multilayer circuit board is characterized in that a material having fluidity equal to or higher than that of the film base material made of the heat-deformable polymer resin is used.

Examples of the heat-deformable polymer resin constituting the film base material include polycarbonate, polyvinyl chloride, polystyrene, saturated polyester profile, polystyrene, polypropylene, polyphenylene oxide, polysulfone, polyphenylene sulfide, polyacetal, polyamide, and the like. I can do it. The thickness of the film base material made of such a polymer resin is preferably in the range of 10 to 100 μm.

The above-mentioned thick film conductive paste needs to have fluidity equal to or higher than that of the film base material made of the heat-deformable polymer resin, for example, vinyl chloride-
Using a low-melting resin such as vinyl acetate copolymer as a binder,
The composition is made by kneading fine powders of metals such as silver, copper, nickel, gold, platinum, aluminum, etc., and adding a solvent as needed. The metal powder is preferably copper or silver in consideration of conductivity and economical efficiency.

(Function) According to the present invention, on the first film base material made of a heat-deformable polymer resin on which a thick film conductive paste with a heat-deformable resin as a binder is printed as a connection land on the surface area, A plurality of second film base materials made of a heat-deformable polymer resin, on which a thick film conductive paste with a heat-deformable resin as a binder is printed as a connection land on the surface area including the inner surface of the hole previously drilled. By laminating them and heating and pressurizing them, the first film base material on the lower side and its land flow, and the one film base material on the upper side flows through the holes drilled in the plurality of second film base materials. It swells up in the hole. At this time, since a conductive paste constituting the land is used that has fluidity equal to or higher than that of the film base material made of the heat deformable polymer resin, it swells together with the first film base material on the lower side. The landed land is connected to the lands of the plurality of second film base materials disposed thereon, and reaches the land formed in the area including the inner surface of the hole of the uppermost second film base material, and is well connected. Ru. Therefore, it is possible to manufacture a multilayer circuit board in which highly reliable through holes are formed that connect multiple layers without disconnection.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Example First, a 30 μm thick 'N1 film base material 11 made of polycarbonate (heat distortion temperature: 135°C) was prepared. vinyl chloride-vinyl acetate copolymer (copolymerization ratio, 86
: 14) was used as a binder, and a thick film conductive paste containing a predetermined amount of fine silver particles having an average particle size of 5 μm was screen printed to form connection lands 12. In this screen printing process, the film base material 11. A wiring (not shown) connected to the land 12 was formed on the surface of the substrate. Further, the binder of the conductive paste has a heat distortion temperature of about 70° C., which is slightly higher due to the inclusion of silver particles, but has a property that the heat distortion temperature is sufficiently lower than that of the base material.

Further, after forming holes 13 in a plurality of (for example, three) second film base materials 11b+ to fibs each having a thickness of 30 μm and made of polycarbonate having the above-mentioned heat distortion temperature, A connecting land 14 was formed in a surface area including the inner surface of the hole 13 by screen printing a membrane conductive paste. In this screen printing process, the land 1 is formed on the surface of each film base material 11□ to 11°.
A wiring (not shown) connecting to 4 was formed.

Next, the first film base material 11. is placed between a fixed plate (not shown) of a heat press machine. and second film base material 11b1~
1 lbi were stacked one after another so that their lands 12 and 14 matched (as shown in FIG. 1(A)). Subsequently, the film base material 11. ．． 11
□~11h3 at temperature 160~180℃, pressure lO~20
It was hot pressed under the condition of kg/e2. At this time, the film base materials 11-, llb+ to lLi are plastically deformed, and the lands 12.14 made of conductive paste having a lower heat deformation temperature than the base materials 11- and llb+ to Hb3 have good fluidity. 1 film base material 11. The land 12 raised together with the second film base material 11b+
While being connected to the land 14 of 111b2, it reaches the land 13 formed in the area including the inner surface of the hole 13 of the uppermost film base material 11b3, and is well connected. As a result, as shown in FIG. 1(B), the wiring (not shown) of the first film base material and the wiring (not shown) of the plurality of second film base materials are connected by the through holes 15 without disconnection. A highly reliable multilayer circuit board 1B with good connections could be manufactured.

Comparative Example First, a 30 μm thick first film base material 21 made of polycarbonate (heat distortion temperature: 135° C.). A thick film conductive paste containing a predetermined amount of fine silver particles having an average particle size of 5 μm was screen printed on the surface of the substrate using an epoxy resin, which is a thermosetting resin, as a binder to form connection lands 22. In this screen printing process, the film base material 11. A wiring (
(not shown) was formed. Further, the binder of the conductive paste has a heat distortion temperature of approximately 150° C., which is slightly higher due to the inclusion of silver particles, and thus has a property of having a heat distortion temperature higher than that of the base material.

Further, after drilling holes 23 in a plurality of (for example, three) second film base materials 21, 1 to 21° having a thickness of 30 μm and made of polycarbonate having the heat distortion temperature described above, the same method as described above is performed. A thick film conductive paste of the same composition is screen printed to form connection lands 2 on the surface area including the inner surface of the hole 23.
4 was formed. In this screen printing process, wiring (not shown) connected to the land 24 was formed on the surface of each film base material 11, 1 to 1 lbs.

Next, the first film base material 21. is placed between a fixed plate (not shown) of a heat press machine. and second film base material 21,1~
21b3 were stacked one after another so that their lands 22 and 24 matched (as shown in FIG. 2(A)). Subsequently, the film base material 118.11 is pressed by the fixed plate of the heat press machine.
．． ~11.3 as in Example, temperature 160~180°C,
Hot pressing was carried out at a pressure of 10 to 20 kg/cm2.

As a result, in the obtained multilayer circuit board 25, as shown in FIG.
The wiring of the first film substrate (not shown) and the wiring of the plurality of second film substrates (not shown) could not be made good due to the through holes.

In addition, although three second film base materials were used in the above example, highly reliable through holes can be similarly formed using two or four or more second film base materials. It is.

[Effects of the Invention] As detailed above, according to the present invention, the film base material and the thick film conductive paste have a structure in which they are integrally crimped, and the multiple layers are connected by highly reliable through-holes that do not cause disconnection. A method for manufacturing a multilayer circuit board through simple steps can be provided.

[Brief explanation of drawings]

FIGS. 1(A) and (B) are cross-sectional views showing the manufacturing process of a circuit board in an embodiment of the present invention, and FIGS. 2(A) and (B)
3 is a cross-sectional view showing the manufacturing process of a multilayer circuit board of a comparative example.
Figures (A) and (B) are cross-sectional views showing the manufacturing process of a circuit board according to a conventional method, and Fig. 4 is an enlarged cross-sectional view of a main part of the circuit board of Fig. 3 (B). 11-, llb+ to 1lbi... film base material, 1
2.14... Connection land, 13... Hole, 15...
・Through hole, 16...Multilayer circuit board.

Claims (1)

[Claims] A first film base material made of a heat-deformable polymer resin on which a thick-film conductive paste with a heat-deformable resin as a binder is printed as a connection land on the surface area, and includes an inner surface of a hole drilled in advance. A plurality of second film base materials made of a heat-deformable polymer resin, each of which has a thick film conductive paste with a heat-deformable resin as a binder printed on the surface area as a connecting land, are laminated, and each film is separated by heat and pressure. When manufacturing a multilayer circuit board by integrating the land and the film base material by pressure bonding to form a through hole that conducts between the upper and lower parts, the conductive paste has fluidity equivalent to or equal to that of the film base material made of the heat-deformable polymer resin. A method for manufacturing a multilayer circuit board characterized by using a material higher than that.