JPH0629663A - Method for manufacturing multilayer circuit board - Google Patents

Abstract

(57) [Abstract] [Purpose] After forming a via hole, stacking unit circuit boards through a prepreg and forming a through hole in the multilayer board, formation of a highly accurate wiring pattern on the unit circuit board. Provided is a method for manufacturing a multi-layer circuit board which is made possible. When manufacturing a multi-layer substrate in which unit circuit boards are laminated via prepreg, an insulating substrate 1 having conductive layers 2 on both sides and having through holes 3 for forming a via hole is laminated via a prepreg. The wiring pattern 6 is formed on the surface to be formed, and the through hole 3 for forming the via hole is filled with the curable conductive material 4 and cured to electrically connect the conductive layers on both sides to obtain the unit circuit board 5. After that, the unit circuit board 5
Are laminated via the prepreg 7, then through holes 8 for through holes are provided in the laminated body 9, plating 10 is applied to the conductive layer and the through holes for through holes, and then the wiring pattern 11 is formed.
Is a method of manufacturing a multilayer circuit board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for manufacturing a multilayer circuit board. For details, after forming the via hole,
A method for manufacturing a multilayer circuit board, which enables formation of a highly accurate wiring pattern on the unit circuit board when the unit circuit boards are laminated via a prepreg and a through hole is formed in the multilayer circuit board.

[0002]

2. Description of the Related Art Conventionally, as a method for manufacturing a multi-layer circuit board having so-called interstitial via holes, which is formed by laminating unit circuit boards having via holes via prepregs, insulation having conductive layers on both sides A through hole for forming a via hole is provided on the substrate by drilling, the through hole is subjected to chemical plating / electroplating, and then a wiring pattern is formed on a conductive layer on a surface to be laminated via a prepreg, and the unit circuit board is formed. After laminating through the prepreg, through holes for through holes are provided in the laminated body,
It is generally manufactured by performing chemical plating / electroplating again and then forming a wiring pattern on the outermost layer.

[0003]

However, in the multilayer circuit board having the interstitial via hole obtained by the above method, it is necessary to repeatedly perform chemical plating / electroplating in forming a via hole and forming a through hole. is there. In the above method, in order to ensure the reliability of the through hole, the plating thickness of one time is 25 μm or more, so that the plating thickness of the outermost layer, which is subjected to the plating treatment many times, exceeds 50 μm, and in this layer, There is a problem that it is difficult to form a wiring pattern with high accuracy. In order to solve such a problem, a method has been proposed in which plating is performed one time thinner than usual to facilitate patterning. However, the multilayer circuit board obtained by such a method is resistant to environmental changes such as thermal shock. Currently, the connection reliability of through holes is poor.

[0004]

In view of the above problems, the present inventors have made earnest studies to develop a method for manufacturing a highly reliable multilayer circuit board without increasing the plating thickness of the outermost layer. . As a result, the through holes are filled with a curable conductive material, and the unit boards in which the conductive layers on the front and back sides are electrically connected by curing are laminated through the prepreg, thereby forming the outermost conductive layer of the multilayer circuit board. It was found that a fine pattern can be easily formed in the layer without increasing the thickness and a multilayer circuit board having highly reliable interstitial via holes can be formed, and the present invention is completed. I arrived.

That is, the present invention provides a prepreg for an insulating substrate having conductive layers on both surfaces and a through hole for forming a via hole when manufacturing a multilayer substrate in which unit circuit boards are laminated via the prepreg. A wiring pattern is formed on the surface to be laminated via, and a through hole for forming the via hole is filled with a curable conductive material and cured to electrically connect the conductive layers on both sides to obtain a unit circuit board. After that, the unit circuit boards are laminated via a prepreg, then through holes for through holes are provided in the laminate, and the conductive layer and the through holes for through holes are plated, and then a wiring pattern is formed. And a method of manufacturing a multilayer circuit board.

In the present invention, the insulating substrate used for manufacturing the unit circuit board is not particularly limited, and those having known materials and structures can be used without limitation. Typical examples are paper base material-phenolic resin laminated board, paper base material-epoxy resin laminated board, paper base material-polyester resin laminated board, glass base material-epoxy resin laminated board, paper base material-Teflon. Resin laminated substrate, glass substrate-polyimide resin laminated substrate, glass substrate-BT (bismaleimide-triazine)
A synthetic resin substrate such as a resin resin laminated substrate or a composite resin substrate, a flexible substrate such as a polyimide resin or a polyester resin, a metal-based insulating substrate obtained by insulating a metal such as aluminum, iron, or stainless with an epoxy resin or the like, or Examples include ceramic substrates.

In the present invention, the insulating substrate has conductive layers on both sides. The material of this conductive layer is not particularly limited. Examples of typical materials include copper, nickel, and aluminum. The thickness of the conductive layer is not particularly limited, but generally 5 to 70 μm is suitable.

First, a through hole for a via hole is provided in an insulating substrate having conductive layers on both sides. The diameter of the through hole is not particularly limited and can be set arbitrarily. In general, the diameter of the through hole may be selected from a hole diameter that is large enough to fill the curable conductive material, usually 0.2 mm or more, and preferably 0.3 to 2 mm. As a method for forming the through holes for the via holes, known means similar to those for producing a usual circuit board such as drilling, punching, and laser processing are used without particular limitation.

In the present invention, the through hole is filled with a curable conductive substance which gives a cured product having conductivity.
The curable conductive substance is made into a paste by mixing a conductive material such as gold, silver, copper, nickel, lead and carbon and a crosslinkable curable resin such as an epoxy resin and a phenol resin together with an organic solvent if necessary. Known curable conductive materials can be used. Among these curable conductive materials, an etching solution used for etching for forming a wiring pattern, for example, ferric chloride etching solution, cupric chloride etching solution, ammonium persulfate etching solution, sodium persulfate etching solution Those which give a cured product which is not substantially dissolved by an etching solution such as a potassium persulfate etching solution, a hydrogen peroxide / sulfuric acid etching solution, or an alkaline etching solution containing ammonium sulfate complex ions as a main component are preferably used.

Further, the above-mentioned curable conductive material has an electric resistance after curing of 1 × in order to obtain good through-hole resistance.
It is preferable to select the conductive material, the curable resin, and the like and adjust the amount used so that it becomes 10 ⁻² Ω · cm or less.

The curable conductive substance may be filled into the through hole for forming the via hole of the insulating substrate so that the curable conductive substance fills the entire space of the through hole. Slightly from both surfaces, specifically 0.1 mm
As described above, it is preferable that the filling amount is 0.1 to 2 mm.

Typical methods for filling the above-mentioned curable conductive material are as follows: a method of applying one or more times by a printing method, a method of press-fitting with a pair of front and back squeegees from both sides of the insulating substrate, and a roll. Means such as a method of filling with a coater or a curtain coater and scraping off excess paint with a squeegee is preferably used.

The curable conductive material filled in the through-hole is cured by a known curing method such as a hot air oven, an infrared oven, a far infrared oven, an ultraviolet curing oven and an electron beam curing oven. What is suitable for curing may be appropriately selected and cured.

In the manufacturing of the unit circuit board, whichever operation is performed first is the operation of forming a wiring pattern on the conductive layer of the insulating substrate and the operation of filling and hardening the through hole for forming the via hole with the curable conductive material. You can go.

Of these, it is preferable to perform an operation of filling a through hole for forming a via hole with a curable conductive material and curing it, and then performing an operation of forming a wiring pattern on the conductive layer of the insulating substrate. In this case, after the curable conductive material is cured, the surface composed of the conductive layer and the cured body of the curable conductive material is ground smoothly, and a plating layer is formed if necessary, and then the conductive layer including the via hole portion is formed. It is preferable that the wiring pattern is formed on the smoothed surface of (1) because the wiring pattern can be formed with high accuracy. Further, by forming the plated layer after grinding as described above, the reliability of the via hole can be improved, and the surface mount component can be mounted on the via hole, thereby increasing the density of the printed circuit board. You can also

As a method for smoothly grinding the surface composed of the conductive layer and the curable conductive material, polishing methods used in ordinary substrate manufacturing processes such as slurry polishing, buff polishing, and scrub polishing are preferably used.

In addition, as a method of forming the plating layer on the smoothed surface, it is general that after the chemical plating, the plating layer is formed on the entire surface of the conductive layer including the via hole portion by electroplating. . As the material of the plating layer used here, a known conductive metal is used without particular limitation, but in general, copper or the like used as the material of the curable conductive substance that gives the cured product having the conductivity is used. It is preferable to select the same material as the conductive metal. The thickness of the plating layer is not particularly limited, but is preferably such a thickness that the connection reliability of the via hole by plating is improved and does not hinder the formation of the fine pattern. As a specific example, the thickness is 25 μm or less, and considering the improvement of the connection reliability of the bihole, the thickness is preferably 5 μm or more.

In the present invention, the conductive layer on the surface laminated on the prepreg of the insulating substrate having conductive layers on both sides is patterned. The patterning method is generally a method of forming an etching pattern with an etching resist and then performing etching. As the etching resist used here, a dry film, a resist ink or the like is used without particular limitation, and it may be appropriately selected and used depending on the fineness of the pattern. Further, as the etching resist pattern, a positive pattern or a negative pattern may be appropriately adopted by the etching method. For example, a positive pattern may be adopted in the etching method typified by the tenting method, and a negative pattern may be adopted in the etching method typified by the solder peeling method and the SES method.

In the present invention, the unit circuit boards are laminated via the prepreg. The lamination is performed so that the surface on which the wiring pattern is formed faces the prepreg side.

As the prepreg used here, known ones used for manufacturing a multilayer circuit board can be used without particular limitation. Generally, a resin such as a solid or high-viscosity epoxy resin is diluted with a solvent and impregnated into a substrate such as glass cloth, and then volatile components such as the solvent are removed in a drying step, and the reaction is advanced to some extent, A non-sticky sheet is preferably used. The unit substrates are stacked by heating and pressing using a general press device. The temperature and pressure for the above-mentioned lamination may be the temperature and pressure suitable for the prepreg. Usually 40-50kg
/ Cm < ² > pressure and 170-180 degreeC temperature. Further, in the present invention, the pin laminating method is adopted to align the positions of the through holes of the unit substrate.

After stacking the unit circuit boards, through holes for through holes are provided in the laminate, a plating layer is formed on the surface of the conductive layer of the laminate including the through holes, and then the plating layer is patterned. To be done.

As the method of forming the through holes, the formation of the plating layer, and the patterning method, the general method described in the manufacture of the unit circuit board is used without particular limitation.

[0023]

According to the method of the present invention, after forming the via hole, the unit circuit boards are laminated through the prepreg, and when forming the through hole in the multilayer board, the number of plating treatments can be reduced, and the laminated body It is possible to prevent the plating thickness of the outermost layer from becoming thick and the etching accuracy from decreasing during pattern formation. Further, the formed via hole is filled with a cured body of a curable conductive material, so that the thickness of the plated layer in the through hole can be sufficiently ensured.

Therefore, a highly accurate wiring pattern can be formed on the unit circuit board, and the via hole and the through hole are stable against environmental changes such as thermal shock, so that the multilayer circuit is highly reliable. It is possible to manufacture the substrate.

Further, in the present invention, when the surface composed of the cured body of the curable conductive material filled in the unit circuit board and the conductive layer is ground smoothly and the smoothed surface is plated. In addition to improving the reliability of the via hole, it is possible to further improve the accuracy of the unit circuit board gap, and further, to provide a multilayer circuit board on which surface mount components can be mounted on the via hole. Can be manufactured.

[0026]

EXAMPLES Examples will be shown below for specifically explaining the present invention, but the present invention is not limited to these examples.

Example 1 A curable paste that gives a cured product having conductivity was prepared by the following method, and a printed circuit board was manufactured. That is, average particle size 6.8 μm, tap density 2.99 g
/ Cm ³ , dendritic electrolytic copper powder having a specific surface area of 4200 cm ² / g, linoleic acid to the copper powder surface 0.25 × 10 ^-5 m
The ingredients were mixed at a ratio of mol / cm ² and premixed in a mortar for 15 minutes under a nitrogen atmosphere. The pretreated copper powder thus obtained was mixed with neopentyl glycol glycidyl ether (epoxy equivalent = 150) / novolac type phenol resin (hydroxy equivalent = 105) = 74/26 (weight ratio).
456 parts by weight to 100 parts by weight of the binder, and 2.8 parts by weight of 2-ethyl-4-methylimidazole to 100 parts by weight of the binder, and then kneaded for 30 minutes with a three-roll mill. As a copper paste.

A multilayer circuit board was manufactured according to the process shown in FIG. That is, (a) a 0.4 mm-thick glass base epoxy resin copper-clad laminate is used as the insulating substrate 1 having the conductive layer 2 on both sides, and (b) a diameter of 0.3 mmφ.
The through hole 3 of No. 3 was created by drilling. (C) The through hole 3 was filled with the copper paste prepared by the above method as the curable conductive material 4 by the screen printing method. The copper paste was cured in an electric furnace under the conditions of 80 ° C-60 minutes and 180 ° C-60 minutes. Next, (d) the wiring pattern 6 was formed on the conductive layer on the surface to be laminated via the prepreg 4 to obtain the unit circuit board 5. Next, (e) 40 kg / c of the unit substrate is passed through a prepreg 7 having a thickness of 0.3 mm.
m ² and 170 degreeC, it heated and pressurized and laminated. (F)
Through holes 8 having a diameter of 0.6 mm were formed in the laminated plate 9 by drilling. Next, (g) chemical plating and electroplating are applied to the entire laminated plate including the through holes 86 to obtain a thickness of 25 μm.
m copper plating layer 10 was formed. Then, (h) a wiring pattern 11 was formed on the outermost conductive layer of the laminated plate to obtain a multilayer circuit board having interstitial by-holes.

The outermost conductive layer has a line width of 100 μm.
It was possible to form a wiring pattern. Also,
As a result of the thermal shock test by the hot oil test, 5
It had a durability of 00 times or more.

Example 2 A printed circuit board was manufactured according to the steps shown in FIG. That is, up to the step (c) of Example 1, after the curable conductive material was filled and cured in the same manner, (a) the 320th and 600th buffs were sequentially used to obtain a cured body of the cured copper paste. The protruding surface was polished to smooth the conductive layer containing the cured body. Next, (b) the smoothed conductive layer surface was subjected to chemical plating and electroplating to form a copper plating layer 13 having a thickness of 10 μm. (C) A wiring pattern 6 was formed on the surface of the conductive layer on which the plated layer was formed, which was laminated via the prepreg, to obtain a unit circuit board. Then (g)
The circuit board through a prepreg 7 having a thickness of 0.3 mm,
The layers were laminated under heat and pressure under the conditions of 40 kg / cm ² and 170 ° C. (D) A through hole 8 having a diameter of 0.6 mmφ was formed in the laminated plate 9 by drilling. Next, (e) the entire laminated plate including the through hole 8 was subjected to chemical plating and electroplating to form a copper plating layer 10 having a thickness of 25 μm. After that, (j) the wiring pattern 11 was formed on the outermost conductive layer having the plated layer to obtain a multilayer circuit board having interstitial by-holes.

The outermost conductive layer has a line width of 100 μm.
It was possible to form a wiring pattern. Also,
As a result of the thermal shock test by the hot oil test, 5
It had a durability of 00 times or more.

[Brief description of drawings]

FIG. 1 is a process drawing showing a typical embodiment of the method of the present invention.

FIG. 2 is a process drawing showing a typical embodiment of the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Conductive layer 3 Through hole for forming via hole 4 Curable conductive substance 5 Unit circuit board 6 Wiring pattern 7 Prepreg 8 Through hole for forming through hole 9 Laminated plate 10 Wiring pattern 11 Wiring pattern 12 Curable conductive substance Hardened material 13 Plating layer

Claims (1)

[Claims] 1. When manufacturing a multi-layer substrate in which unit circuit boards are laminated via a prepreg, conductive layers are provided on both sides,
A wiring pattern is formed on the surface of the insulating substrate having a through hole for forming a via hole to be laminated via the prepreg, and the through hole for forming a via hole is filled with a curable conductive material and cured to form a double-sided surface. After electrically connecting the conductive layers to obtain a unit circuit board, the unit circuit boards are laminated through a prepreg, then through holes for through holes are provided in the laminated body, and the conductive layers and through holes for through holes are formed. A method for manufacturing a multilayer circuit board, comprising forming a wiring pattern after plating the holes.