JP3324660B2 - Multilayer wiring board and adhesive film used for it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interlayer connection structure for a multilayer wiring board.

[0002]

2. Description of the Related Art A multilayer wiring board can incorporate a signal circuit, a power supply, an earth circuit, and the like, and is therefore often used in various electronic devices as an effective method for increasing the wiring density. A typical method of manufacturing a conventional multilayer printed wiring board is to cover the portions other than the interconnections with a coverlay film or the like and obtain electrical insulation, and electrically connect the wiring patterns of each layer to each other by copper plating or the like. It has been done. In addition, as a relatively new attempt, the interconnects are covered with conductive particles while obtaining insulation by covering other than the interconnects with a coverlay film, mask film, resist film, etc. (collectively referred to as cover films hereinafter). It has also been proposed to connect the wiring patterns of each layer to each other using a material made of a dispersed adhesive (for example, Japanese Patent Application Laid-Open No. 61-49499 and Japanese Patent Application Laid-Open No. 2-3659).
No. 3), and solder particles are used as the conductive particles in this case.

[0003]

In each of the above-mentioned conventional methods, since a portion other than the interconnecting portion is covered with a cover film, two layers of the cover film exist between the opposing wiring boards, and when a multilayer wiring board is formed, the thickness is reduced. It was difficult to obtain a decrease, which also contributed to the cost increase. As for the interconnection method of the wiring patterns, the method of plating with copper or the like requires a complicated plating step, and has a disadvantage that the copper plating is easily broken when the cover film is thermocompressed. When connecting with a material consisting of conductive particles and an adhesive, since the conductive particles are uniformly dispersed throughout the bonding, the adhesive flows due to thermocompression bonding at the time of connection, and other than the parts that require connection of the wiring pattern However, if the conductive particles are solder, the insulating property is reduced because the cover film is damaged because of the hardness below the melting point, and the insulating property is reduced. It has become impossible to cope with increasingly thinner wiring. The present invention relates to a multilayer wiring board using an interlayer connection which does not require a cover film or a plating step and can cope with thinning of wiring.

[0004]

According to the present invention, conductive particles and an adhesive are provided between two or more double-sided wiring boards each having a wiring pattern formed on an insulating substrate. A multi-layer printed wiring board in which an adhesive layer composed of an adhesive and conductive particles is formed on both sides of an insulating film, and a heat-pressing method for the conductive particles. The present invention relates to an adhesive film whose thermal transformation point is lower than that of an insulating film. Sand
That is, two or more wiring patterns formed on an insulating substrate
Insulating film with a through hole in the main part between double-sided wiring boards
Adhesive layer consisting of conductive particles and adhesive on both sides
After heating and pressurization, conductive particles are collected
A multi-layer wiring board in the middle. Adhesion consisting of adhesive and conductive particles
Agent layer is formed on both sides of the insulating film having through holes
And the thermal transformation point of the conductive particles is lower than that of the insulating film.
(A) metal particles, (b) conductive particles
Or a non-conductive particle surface coated with a conductive layer,
(C) From insulating coated particles obtained by coating conductive particles with an insulating layer
2. The contact used for the multilayer wiring board according to claim 1, which is selected.
It is a wearing film.

The configuration of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view illustrating an embodiment of the present invention. Reference numeral 1 denotes an insulating substrate made of phenolic resin, epoxy resin, polyimide, etc., paper, glass cloth, glass nonwoven fabric,
Or the like, which is impregnated into a base material such as polyester, heated and pressed, a plastic film such as polyester or polyimide, a metal such as Al or Fe, and a ceramic. Wiring pattern 2
Although formed on both sides of the insulating substrate 1 as shown in FIG. 1, the outermost layer when a multilayer wiring board is formed may be one side. The wiring pattern 2 may protrude from the substrate surface as shown in FIG. 1 or may have a flat shape or a concave shape (not shown). From the viewpoint of connection stability, it is preferable that at least one of the opposed wiring patterns protrudes. These wiring patterns can be formed by general means such as a tenting method, an additive method, and a transfer method. An adhesive layer may be present between the insulating substrate 1 and the wiring pattern 2.

In the interlayer connection method, a wiring pattern 2 requiring connection is provided between first and second wiring boards 3 and 4.
An adhesive layer composed of conductive particles 5 and an adhesive 6 is laminated and integrated using an adhesive film 10 formed on both sides of an insulating film 8 having a through hole 7 in a main part, and the two wiring boards 3-4
And at the same time, obtain electrical conduction between the wiring patterns 2-2 'requiring these connections. The wiring pattern 2 that needs to be connected here may be the entire pattern or a part of the pattern, and the connection-unnecessary wiring pattern 9 (for example, a via hole) may be present on the connection surface.

The adhesive film suitable for the present invention will be described. As the adhesive 6, a thermoplastic material used for a sheet or the like, or a curable material using energy such as heat, light, or an electron beam can be widely applied. Curable materials are preferred because they have excellent heat resistance and moisture resistance of the multilayer wiring board.Epoxy-based adhesives and imide-based adhesives, among others, have excellent adhesiveness and heat resistance due to their molecular structure and can be set over a wide curing time. Is preferred. Epoxy-based adhesives are, for example, high-molecular-weight epoxies, solid epoxies, liquid epoxies, and epoxies modified with urethane, polyester, NBR, etc. as the main components, and added with curing agents, catalysts, coupling agents, fillers, etc. Is common. When these materials are high-purity products in which Na ions and Cl ions of the extraction water are 20 ppm or less, it is preferable that the electric corrosion resistance of the multilayer wiring board is improved.

As the conductive particles 5, Au, Ag, Ni,
There are metal particles such as Cu, W, Sb, Sn, and solder, carbon, and the like, and the conductive layer described above is formed by coating the above-mentioned conductive layer on a polymer core material such as non-conductive glass, ceramics, and plastic. But it is good. Further, the above-mentioned insulating coated particles formed by coating the conductive particles and the insulating layer, and the combination use of the conductive particles and the insulating particles are also extremely useful for thinning the circuit. Heat-melted metal such as solder or polymer nucleus material such as plastic with a conductive layer formed has a thermal transformation point such as melting point and glass transition point, so it has deformability by heating or pressing. This is preferable because the contact area with the circuit at the time of lamination increases and the reliability improves. In this case, if the thermal transformation point of at least the core material of the conductive particles is low due to the insulating film, the insulating film 8 of the adhesive film is not damaged by heating and pressing during lamination and integration, and the interlayer insulating property is highly maintained. It is preferred because it sags. In particular, when a polymer is used as a nucleus, it does not exhibit a melting point unlike solder, so that a softened state can be widely controlled by a connection temperature, and it is easier to cope with variations in thickness and flatness of a wiring board or a wiring pattern, which is more preferable. Also, in the case of hard metal particles such as Ni and W, the conductive particles pierce the wiring pattern, so that a low connection resistance can be obtained even when an oxide film or a contaminant layer is present on the wiring pattern. It is also effective in suppressing expansion and contraction due to the fixation of the fixing member, and reliability is improved. Therefore, the particle size in the case of hard metal particles is determined by the distance between wiring patterns that require connection (thickness after connection)
It is preferable that the particle size is slightly larger than the above, and when the particle size is smaller than that, it is preferable that the particles are aggregated. In principle, the number of the conductive particles may be one in a portion of the wiring pattern that requires connection, but it is preferable to use five or more because connection reliability is further improved. The particle size is preferably equal to or less than the distance between adjacent wiring patterns in order to cope with thinning.

As the insulating film 8 having the through hole 7 in the main part, a general insulating film such as polyimide, polyethylene terephthalate, or polyethylene may be used, and a thin film as possible is preferable from the viewpoint of reducing the thickness and cost of the multilayer wiring board. Transmural hole 7 is formed on the conductivity required portion of the interlayer, including the adhesive layer conductive particles 5 and consisting of an adhesive 6
Configuration (Figure 1, 7 B), only the through-holes not include an adhesive layer insulating film (Fig. 1, 7 A) may be used. The latter is preferred from the viewpoint of workability .

At the time of lamination and integration, a portion of the wiring pattern surface that requires connection is positioned and heated and pressed. At this time, a so-called pin lamination method in which, for example, a through-hole is formed in a predetermined number of wiring boards and an adhesive film that require lamination and alignment is performed with pins or the like is preferable. As a method of integration, a press or roll laminator is used. A general method such as the above may be used. By filling the through-holes of the pin lamination method with a conductive adhesive or plating through holes,
Electrical connections between all layers can also be obtained.

FIG. 2 is a schematic sectional view showing the structure of FIG. 1 after lamination and integration. Due to the heating and pressing, the adhesive flows and the conductive particles 5 need to be connected on the wiring pattern.
The adhesive concentrates on 2 'to enable electrical connection, the adhesive flows and fills and adheres between the two substrates 1-1', and the insulating film 8 maintains interlayer insulation. Also, the connection unnecessary wiring pattern 9 is similarly kept insulative. By arbitrarily laminating this layer, an arbitrary multilayer wiring board can be obtained. Preferred conductive particles are those obtained by forming a conductive layer on a hot-melt metal such as solder or a polymer nucleus material such as plastic.
Is deformed into a portion 2-2 'requiring connection on the wiring pattern, the contact area with the interposed pattern is increased, the connection resistance is stabilized, and the reliability is improved. Although the optimum filling amount of the adhesive can be controlled by the thickness of the adhesive, it is preferable that the unnecessary portion is removed by flowing out to the end by laminating and integrating, so that air bubbles are less mixed.

[0012]

According to the present invention, an adhesive comprising conductive particles and an adhesive on both sides of an insulating film having a through hole in a main part between a plurality of double-sided wiring boards each having a wiring pattern formed on an insulating substrate. Since it is a multilayer printed wiring board that forms layers and is laminated and integrated by heating and pressing, it does not require a cover film because it is in contact with the insulating adhesive except for the interconnects, and the interconnects are electrically connected by conductive particles. No plating is required because it is obtained. Since the conductive particles of the present invention are intensively flown and arranged only in the main part of the wiring pattern by the constant lamination, there is no leak between adjacent patterns, and the conditions of thermocompression bonding can be widely applied. Even if conductive particles are present in portions other than the connection portion, the insulating property is maintained because the insulating film exists between the layers, and the concentration thereof is low, so that leakage does not occur in the adjacent wiring pattern. Therefore, the connection resistance is stabilized, the reliability is improved, and it is possible to cope with the thinning of the circuit. In addition, a multilayer wiring board which is effective in reducing the thickness and cost of the multilayer wiring board can be obtained very easily.

Further, the adhesive film suitable for the present invention is obtained by forming an adhesive layer comprising an adhesive and conductive particles on both sides of an insulating film, so that the conventional cover film and the adhesive for bonding the same are originally formed. Since they are integrated, a multilayer printed wiring board effective for cost reduction can be obtained very easily. In particular, when a polymer is used as the core as the conductive particles, the softening state can be widely controlled by the connection temperature, and it is easy to cope with variations in the thickness and flatness of the wiring board or wiring pattern.

[0014]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. In addition, a four-layer wiring board in which two double-sided boards are connected to each other for easy understanding will be described. However, one of the two double-sided boards may be a single-sided board, or a multilayer wiring board having more than four layers may be used. Applicable.

Examples 1 to 4 An adhesive 10 was applied to both sides of a polyimide film having a thickness of 50 μm.
A double-sided board formed by forming a copper foil 18 μm through
A wiring board on which pattern printing, etching, and the like were performed was prepared. The minimum diameter of the wiring pattern that requires connection is 50 μm
Met. Punch a through-hole corresponding to the wiring pattern requiring connection on the polyimide film 25 μm, and apply a 15 μm thick adhesive mainly composed of high molecular weight epoxy (Na of extracted water after extraction at 100 ° C. for 10 hours with pure water) on both sides. Ions and Cl ions are each 10 ppm or less). The following conductive particles were uniformly dispersed in the adhesive in an amount of 12% by volume to obtain an adhesive film of the present invention. The conductive particles used here were plated plastic spheres having a particle diameter of 10 μm having a Ni / Au composite conductive layer on the surface of a core material made of cross-linked polystyrene (Example 1), and carbonyl method Ni having an average particle diameter of 7 μm (Example 1). 2), melting point 1 with an average particle size of 15 μm
80 ° C. solder particles (Example 3), and insulating coated particles (Example 4) obtained by coating the particle surface of Example 1 with nylon having a thickness of about 0.2 μm. After aligning the through-holes formed on the four sides of the wiring pattern with the through-hole of the adhesive film and the other wiring board with the wiring pattern that requires connection of one of the wiring boards with pins, the through-hole portion is conductively bonded. Filling with the agent,
180 ° C 20 kg / cm ² For 30 minutes to cure the adhesive. As described above, a four-layer wiring board in which two double-sided boards are connected between layers is obtained. Examples 1 to 4 all showed sufficient interlayer connection characteristics.

Example 5 Adhesive 1 was applied to both sides of a glass epoxy substrate having a thickness of 0.2 mm.
A wiring board was prepared by performing pattern printing, etching, and the like on a double-sided board formed with a copper foil of 18 μm through 0 μm. The minimum diameter of the wiring pattern that requires connection is 20
μm. Using the adhesive film of Example 1, the same positioning, heating, pressurizing, and curing of the adhesive as in Example 1 were performed to obtain a four-layer wiring board in which two double-sided boards were interconnected.
Example 5 also showed sufficient interlayer connection characteristics.

[0017]

As described above, according to the present invention, a cover film and a plating step are not required, and it is possible to cope with thinning of a circuit, and in addition, a connection effective for reducing the thickness of a multilayer wiring board and reducing costs. A multilayer wiring board with improved reliability can be obtained very reasonably easily.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of a configuration at the time of manufacture of the present invention.

FIG. 2 is a schematic sectional view showing one embodiment of the present invention after lamination and integration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating board 2 Wiring pattern 3 1st wiring board 4 2nd wiring board 5 Conductive particle 6 Adhesive 7 Through hole 8 Insulating film 9 Connection unnecessary wiring pattern 10 Adhesive film

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kazuhiro Isaka 1500 Oji Ogawa, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. (72) Inventor Yutaka Yamaguchi 1500 Ogawa, Shimodate-shi, Ibaraki Pref. Hitachi Chemical Industries, Ltd. Shimodate Research Laboratory (56) References JP-A-61-49499 (JP, A) -79268 (JP, A) JP-A-2-36593 (JP, A) JP-A-61-187394 (JP, A)

Claims (2)

(57) [Claims] 1. An insulating substrate on which a wiring pattern is formed.
Between two or more double-sided wiring boards, an adhesive layer composed of conductive particles and an adhesive is disposed on both sides of an insulating film having a through hole in a main part, and the conductive particles are applied to the main part after lamination and integration by heating and pressing.
Multilayer wiring board with children concentrated . 2. An adhesive layer comprising an adhesive and conductive particles penetrates.
It is formed on both sides of the insulating film having holes, the thermal transformation point of the conductive particles is lower temperature than the insulating film ,
The conductive particles are (a) metal particles, (b) conductive or non-conductive
A conductive layer coated on the surface of conductive particles, (c) conductive
Not selected from insulating coated particles in which particles are coated with an insulating layer
An adhesive film used for the multilayer wiring board according to claim 1 .