JPS61294896A - Manufacture of 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 [Field of Application of the Invention] The present invention relates to a printed circuit board, and particularly to a method for manufacturing a multilayer printed circuit board suitable for electronic equipment requiring high density.

[Background of the invention]

Conventional methods for manufacturing multilayer printed circuit boards include, for example, printed circuit board technology and its quality assurance J, pp. 278-280, edited by Toshiba Corporation's Circuit Board Department (published by Applied Technology Publishing). Two or more inner layer materials with a circuit pattern formed on a stretched laminate are laminated with a semi-cured adhesive material made of resin-impregnated glass cloth sandwiched between them, and then integrated by pressure and heating, followed by multilayer printing. Holes were drilled through the entire circuit board, and these holes were plated with copper to connect the outer layer patterns to the inner layer patterns, or to connect the inner layer patterns to each other.

On the other hand, with the recent increase in the density and speed of semiconductor devices, there is a need for even higher density multilayer printed circuit boards.
For this reason, the plate thickness tends to be large and the hole diameter tends to be small.

As a result, when conventional methods are applied, drilling and copper plating are required for narrow and deep holes, the drill breaks during the drilling process, and the plating solution penetrates into the hole during the copper plating process, causing problems with reliability. It has become to.

[Purpose of the invention]

An object of the present invention is to provide a method for manufacturing a multilayer printed circuit board that does not require through-hole drilling and through-hole plating, which are problems in conventional methods.

[Summary of the invention]

Instead of drilling through holes and plating through holes in a multilayer printed circuit board, the present invention
Holes are made in a laminate with copper foil on both sides, a circuit pattern is formed except for at least one outermost layer, and then multiple laminates are bonded under heat and pressure with an adhesive between them to form a board. After that, the stacked holes are irradiated with a laser to penetrate these holes as through holes in the substrate, and then a conductive liquid adhesive is supplied from the outermost layer to the through holes to establish continuity between each layer.A multilayer printed circuit is created. It is characterized by the method of manufacturing the board.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the process of manufacturing a multilayer printed circuit board from a laminate 1. As shown in FIG. A hole 2 is made in a laminate plate 1 with copper coated on both sides, and copper plating 3 is applied so as to connect the upper and lower surfaces of the laminate plate 1. Then (di, ,tel,
A circuit pattern is formed by a well-known method, as shown in Fig. However, no circuit pattern is formed on the outermost layer 6 and the lower outermost layer 6. Note that a pad 4 is provided for each hole 2 where it is desired to make a three-dimensional circuit connection between the outermost layers 6. Next, these laminate plates 1 are laminated with adhesive 7 in between so that the outermost layer 6.6 becomes the outer surface, and the substrate shown in FIG. 1 (F) is completed by pressurizing and heating to integrate. .

At this time, the hole 2 is filled with the adhesive 7, so the carbon dioxide laser 8 scans the substrate, and the adhesive 7 in the hole 2 is evaporated and removed, thereby forming the through hole 9. Note that when the laminate plate 1 is heated under pressure to integrate the laminate,
The respective laminated plates 1 may be misaligned with each other, and the positions of the holes 2 may be slightly misaligned. However, the carbon dioxide laser 8 irradiated into the hole 2 is reflected on the steel plating 3, thereby heating the copper plating 3 and the copper foil, thereby heating and vaporizing the adhesive 7 around the copper plating 3. Carbon dioxide laser 8 to hole 2
Although most of the adhesive 7 in the hole 2 evaporates and scatters due to the irradiation, some molten resin residue remains in the hole 2. This can be removed.

Next, as shown in FIG. 1(i), when the conductive adhesive 10 is swept over the outermost layer 6 with a squeegee 11 using a paste printing method, the inside of the first through hole 9 is filled with the conductive adhesive 10. Then, the conductive adhesive 10 is cured in this state.

At this time, if the coefficient of thermal expansion of the conductive adhesive 10 is made equal to the coefficient of thermal expansion in the vertical direction of the board, even if the board expands and contracts due to temperature cycles, the conductive adhesive 10 and the copper plating around the through hole 9 will remain intact. Since no strain occurs between the conductive adhesive 1o and the copper plating 3, poor adhesion between the conductive adhesive 1o and the copper plating 3 or cracks do not occur inside the conductive adhesive 1o. The vertical thermal expansion coefficient of the substrate is considered to be the weighted average of the thermal expansion coefficient of the copper plating 6 or copper foil and the thermal expansion coefficient of the post-adhesive 7 or the resin constituting the base material. Conductive adhesive 1 made by mixing resin with metal powder such as copper
By configuring 0, the thermal expansion coefficient of the conductive adhesive 10 can be approximately matched to the vertical thermal expansion coefficient of the substrate.

Next, after removing the conductive adhesive 10 attached to the substrate surface, the outermost layer 6 and the outer layer pattern of 6 are formed.
As shown in Figure (J), a multilayer printed circuit board is completed in which the circuit patterns of each layer are connected by the conductive adhesive 10.

In the above embodiment, a carbon dioxide laser is used to melt and evaporate the adhesive 7 in the hole 2, but other lasers such as an argon laser may be used as long as the laser melts and evaporates the resin in a bath.

Furthermore, although the circuit pattern is formed on the outermost layer 6 together with the outermost layer 1-6 later, the circuit pattern may be formed on the outermost layer 6 in advance.

〔Effect of the invention〕

According to the present invention, it is possible to omit through-hole drilling and copper plating steps when manufacturing a multilayer printed circuit board. Therefore, there is no need to consider the reliability of drill breakage and copper plating, which were problems in the past. Furthermore, since processes that require a long time can be omitted, costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a laminate and a substrate showing the steps of an embodiment of the present invention. 1... Laminated board 2... Hole 6... Copper plating 4... Pad 6. 6... Outermost layer
7... Adhesive 8... Carbon dioxide laser 9... Through hole 10... Conductive adhesive 11... Squeegee.

Claims (1)

[Claims] Drill holes in a laminate with copper foil on both sides, and make at least 1 hole.
After forming a circuit pattern except for the outermost layer, a plurality of laminates are heat-pressed with an adhesive between them to form a substrate, and then the stacked holes are irradiated with a laser to form the holes. A method for manufacturing a multilayer printed circuit board, comprising: passing through the substrate as a through hole, and then supplying a conductive adhesive from the outermost layer to the through hole in order to establish electrical conduction between each layer.