JPS5890796A - Method of producing multilayer printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer printed wiring board, and more particularly to a method for manufacturing a multilayer printed wiring board in which a printed circuit board is laminated and molded via an insulating adhesive sheet (hereinafter referred to as prepreg).

In recent years, with the increasing density of electronic devices such as ICs and LLs, mounting methods have become diversified, such as the soldering of electronic devices onto a single printed wiring board. There is a growing demand for improved heat resistance of printed wiring boards.

Factors that affect the heat resistance of a multilayer printed wiring board include issues with the printed board material, particularly the adhesive strength of the resin, heat resistance characteristics at high temperatures, moisture absorption characteristics, etc. On the other hand, in the case of the manufacturing method, examples include a dehumidification process after a wet process such as a lamination molding process, a hole-drilling process, a through-hole plating process, and a through-hole plating process. Among these, the multilayer lamination molding process is the most important process in determining the quality of the multilayer printed wiring board, including its heat resistance.

When laminating and molding a multilayer printed wiring board, normally, as shown in FIG. 1, a plurality of printed circuit boards 1 each having a conductor pattern 11 provided on an insulating board are interposed with a desired number of prepregs 2 by known means. The stacked integral objects are sandwiched between suitable holding jigs 3, heated and pressed using a hot press, etc., and laminated and molded. In this case, the heat and pressure applied to the prepreg 2 as an adhesive sheet causes the resin contained in the prepreg 2 to melt and flow to fill the desired location. It is necessary to flow uniformly no matter the location,
In reality, the flow of resin at the periphery of the printed circuit board 1 is greater than at the center. For this reason, a sufficient amount of resin cannot be obtained in the peripheral portion of the printed circuit board 1 to bond the printed circuit boards together.

As a result, holes and peeling occur between the printed substrates, causing a problem of reduced adhesion between the printed substrates. This problem of reduced adhesion between printed circuit boards may become apparent only after the multilayer printed wiring board is soldered, when peeling occurs between the printed circuit boards. In order to improve such heat resistance, it is also necessary to prevent the resin from flowing out of the specified position at the periphery of the printed circuit board. The insulating resin layer between the inner layer conductors in a multilayer printed wiring board must have a constant thickness as much as possible in order to reduce the variation in the design value of the characteristic impedance of the signal circuit. The problem that the thickness of the insulating resin layer between the inner layer conductors becomes larger is also a disadvantage of reducing the thickness of the insulating resin layer between the inner layer conductors.

The present invention eliminates such conventional drawbacks, and when laminating and molding a plurality of printed circuit boards with conductors for printed circuits provided on the surface of an insulating plate with prepreg interposed therebetween, it is possible to It is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board, which is characterized in that a heat-resistant elastic sheet is interposed in the adjacent outer periphery, and the printed circuit board is laminated and molded.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of the present invention, in which 1 is a printed board, 2 is a prepreg, and 4 is a heat-resistant elastic sheet. A conductor pattern 1 is formed on an insulating plate in advance by known means.
1 to form an insulating substrate 1. Next, as shown in FIG. 2, a copper-clad cherry laminate 5 for forming an outer layer pattern is placed on a clamping jig 3 having sufficient rigidity so that the copper foil surface is in contact with the clamping jig 3 described above. “Next, the prepreg 2 is placed on the copper-clad laminate 5, and a frame-shaped heat-resistant 3-unit sheet 4 as shown in FIG. As the heat-resistant elastic sheet 4, silicone rubber, fluorine rubber, etc. can be used, but silicone rubber is most suitable in consideration of the resin's releasability, price, ease of acquisition, etc. The hardness and thickness of the silicone rubber sheet determine the flow of the resin, and the rubber hardness is 30 to 70 degrees, and the thickness is 0.2 to Q, 4% m2), which is the thickness of the commonly used prepreg. .05~Q
Good results can be obtained by using a material that is about 3 mm thick. It is sufficient that the width of the silicone rubber is 3 rrm or more, but it is preferably 5 to 1Q mm for ease of handling. Next, an insulating substrate 1 is placed on the prepreg 2 and the heat-resistant elastic sheet 4.
are placed so that the heat-resistant elastic sheet 4 and the prepreg 2 are sandwiched between the insulating substrate 1 and the steel clad laminate 5.

As for the upper side of the insulating substrate 1, similarly to the lower side of the insulating substrate 1 described above, the prepreg 2'1 and the heat-resistant elastic sheet 4 are sequentially coated.
', the copper-clad laminate 5', and the clamping jig 3' are softened. For example, the temperature of the heating plate of the structure configured in this way is 170~
Place it in a hot press set at 175°C,
For example, when applying a pressure of 25 to 35 kg/cm,
After heating and curing for 0 to 50 minutes and further cooling, the product is removed from the hot press to obtain a laminated body.

In addition, in FIG. 3, the silicone rubber is shown as a frame-shaped integral piece, but strip-shaped pieces divided on four sides of the periphery may also be placed.

As described above, according to the present invention, by suppressing unnecessary flow of resin, a highly heat-resistant multilayer printed wiring board with excellent adhesion between printed boards can be manufactured.

Furthermore, it is also possible to make the thickness of the insulating resin layer between the inner layer conductors and between the inner layer conductor and the outer layer conductor uniform.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional multilayer printed wiring board.
FIG. 2 is a cross-sectional view of the structure of a multilayer printed wiring board according to the present invention. FIG. 3 is a plan view of the elastic sheet. 1°°°°°8 Insulating substrate, 2.2I0-Insulating adhesive sheet)% 3% 3'...... Holding jig, 4.
4'-...Heat-resistant elastic sheet 15%y...
・Copper-clad laminate. Fall 1 Kuchihaya Z Nyomine 3v

Claims (1)

[Claims] In a method for manufacturing a multilayer printed wiring board, in which a plurality of printed circuit boards each having a printed circuit conductor provided on the surface of the insulating board are laminated with an insulating adhesive sheet interposed therebetween, A method for manufacturing a multilayer printed wiring board, characterized by laminating and molding a printed circuit board on the outer peripheral part with a heat-resistant elastic sheet interposed therebetween.