JPS588160B2 - Method for manufacturing multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer printed wiring board laminated with prepregs interposed therebetween.

The structure of a conventional general multilayer printed wiring board is shown in FIG.

Single-sided copper-clad laminate (printed wiring board) 3 forming a surface layer, respectively
, 3, double-sided copper-clad laminates (printed wiring boards) 5 and prepregs 6 forming an intermediate layer 5 are alternately stacked.

Although only one intermediate layer 5 is shown in the figure, generally a large number of intermediate layers 5 are laminated alternately with prepregs 6.

Since the prepregs 6 also serve as spacers, two prepregs 6 are generally arranged between each intermediate layer and between the surface layer and the intermediate layer.

The relative positioning of the surface layer, intermediate layer and prepreg is done by reference pins 1, 1 of the upper and lower molds 2, 2.

That is, the lower surface layer 3, the prepreg 6, the intermediate layer 5, the prepreg 6, . . . the upper surface layer 3 may be fitted into the reference pin 1 in this order.

Incidentally, reference numerals 7 and 7 are release films that prevent the molds 2 and 2 from being contaminated with resin.

Both surface layers 3 and intermediate layer 5 are integrally fixed by prepreg 6 interposed between them by heating and pressing both molds 2, 2 with a lamination press (not shown), and thus multilayer printing is performed. Configure the wiring board.

The prepreg 6 for adhering the surface layer and the intermediate layer or the intermediate layers to each other is generally constructed by impregnating and coating a glass cloth with an uncured resin such as an epoxy resin.

When a single prepreg is heated, the uncured resin shrinks and hardens to bond the printed wiring boards on both sides, but this shrinkage and hardening deteriorates the dimensional stability of the prepreg and multilayer printed wiring board.

That is, when the prepreg shrinks and hardens, it pulls together the printed wiring board that is adhered to it, resulting in dimensional deviations in the printed wiring board as well.

As a result, for example, the land portion of the conductor pattern patterned on the printed wiring board may be misaligned between the two layers, and a through hole that should normally be drilled at the center of the land may be deviated from the center of the land portion in the second layer, for example. As a result, a part of the land portion may end up being located in a place where no land portion is formed.

This means that electrical continuity is broken in the through-hole that is outside the land area, so if a conductor pattern happens to be wired at that position, the result will be the same as a disconnection and should be overlooked. This is a disadvantage that cannot be gained.

In this way, the misalignment of the printed wiring board is caused not by its own shrinkage, but by the shrinkage of the prepreg.

Furthermore, when we measured the positional deviation of this printed wiring board, we found that it occurred not only at the central land but also at the reference pin hole near the edge, and when the reference pin hole was returned to its original position, the maximum The amount of displacement is expressed as the sum of these.

In addition, as a result of various experiments, the prepreg was freed from the reference pin,
That is, it was confirmed that if the prepreg was not inserted into the reference pin, the position amount would be much smaller.

This is because by freeing the prepreg from the restraints of the reference pins, it will shrink freely and have less influence on the printed wiring board, and will not appear as distortion or local displacement. This is thought to be because the traction force exerted on the wiring board becomes smaller.

The present invention is based on the above-mentioned characteristics by removing a part of the prepreg so that it does not touch the reference pin, thereby improving the dimensional accuracy of the printed wiring board.

According to the present invention, the reference pin 1 is not inserted into the prepreg 16 as shown in FIG.

For this purpose, the prepreg 16 may be cut off at four sides including the conventional reference pin hole 18 as shown in broken lines 17 as shown in FIG.
Only the portion 17' of 8' is removed so that it does not touch the reference pin 1.

Since the prepreg 16 is released from the reference pin 1, a positioning pin 9 may be provided for positioning it, but in that case, the pin hole 20 should be located as close to the center of the prepreg as possible to influence the free contraction of the prepreg as much as possible. Make sure not to.

The positioning pin 9 may not be provided.

It should be noted here that the dimensional reference position of the printed wiring board is always measured using the position of the reference pin 1 as the origin, and therefore the positioning pin 9 does not contribute in any way to the measurement of the reference dimension. This means that it is a dimensional deviation in the vicinity of pin 1.

Since a part of the prepreg is removed as shown in FIG. 3 or 4, the printed wiring board is not pulled by the prepreg at least in the vicinity of the reference pin 1 when the prepreg hardens and contracts. Dimensional deviations are also reduced, and the problems mentioned at the beginning are solved.

For the purpose of the present invention, it is preferable that the removed portion of the prepreg be as large as possible, but considering the function of the prepreg as an adhesive layer, it is not possible to reduce the area of the prepreg needlessly, so the cutout portion of the prepreg should be made as large as possible, taking these points into consideration. It will be decided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a typical conventional method for manufacturing a multilayer printed wiring board, FIG. 2 is a diagram similar to FIG. 1 showing a manufacturing method according to the present invention, and FIG. 3 is a diagram showing a prepreg used in the present invention. FIG. 4 is a perspective view showing a modification of FIG. 3. 1... Reference pin, 3, 5... Printed wiring board, 6, 16... Prepreg.

Claims (1)

[Claims] 1. When manufacturing a multilayer printed wiring board by alternately stacking a plurality of printed wiring boards and prepregs while aligning them using reference position reference pins, at least the portion of the prepreg that corresponds to the reference pins is cut out. A method for manufacturing a multilayer printed wiring board, characterized in that the reference pin is inserted only into the printed wiring board.