JPS581560B2 - Heat-resistant composite printed board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printed board structure in which the front and/or back surfaces of a resin multilayer printed board are coated with ceramic.

Recently, multilayer printed boards have been widely used in electronic devices and the like to simplify complicated wiring work and prevent wiring errors.

By the way, a conventional multilayer printed board has a structure as shown in FIG. 1, and is manufactured by the following steps.

A printed board made of copper-clad epoxy resin or the like is printed on both sides (or one side) with a negative film and etched to form an intermediate layer in a predetermined pattern.

Next, several layers of this intermediate layer are stacked and an epoxy adhesive (for example, glass cloth impregnated with epoxy resin) is interposed between them, and then they are bonded under heat using a hot press to form a multilayer printed board 4. Next, holes are made through the printed circuit board at predetermined positions, and a conductive layer, such as copper plating, is applied to the inner wall surface of the hole 6 and the periphery of the opening, and the inner layer wiring patterns 1, 2, and 3 are electrically connected.

The structure described above is a conventional resin multilayer printed board, which has a small dielectric constant and is superior in transmission characteristics compared to ceramics, but is inferior in heat resistance and surface smoothness.

Furthermore, as future electronic computers and the like become larger, integrated circuit components such as LSIs will need to be mounted at a higher density, and such conventional resin multilayer printed boards cannot be expected to have higher mounting density than the current situation. Therefore, it is desired to develop a printed board with excellent heat resistance that can withstand the heat generated by circuit components.

An object of the present invention is to provide a multilayer composite printed board that has heat resistance and surface smoothness similar to ceramics without sacrificing the transmission characteristics and manufacturability of resin multilayer printed boards.

A feature of the present invention is that after coating one or both sides of a resin multilayer printed board with ceramic, a metal adhesion layer is formed on the surface of the ceramic, and the metal adhesion layer is provided so as to protrude onto the resin multilayer printed board through the metal adhesion layer. Electrical connection is made by drawing out the wiring pattern from the conductive part.

By adopting such a structure, the surface of the multilayer printed board can have the heat resistance and smoothness of ceramic, and the inner layer wiring pattern portion can have the combined properties of the resin multilayer printed board with good transmission characteristics.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 2 shows an embodiment according to the present invention.

In FIG. 2, inner layer wiring patterns 1, 2, and 3 are electrically connected by a mesh through-hole conductor 15.

Ceramic 5 is coated on both sides of the resin multilayer printed board 40, and a metal film 7 is deposited on the top surface of the ceramic by sputtering a base metal such as tungsten or titanium to improve adhesion to the ceramic. A metal adhesion layer 8 (Au or the like) of several micrometers is deposited on the surface by electroplating or the like.

A necessary surface pattern can be created by applying an etching mask to the above-described composite printed board of the present invention and etching it.

The structure of the composite multilayer printed board according to the present invention has been described above. Next, the outline of manufacturing of the multilayer printed board will be explained.

FIG. 3 shows a schematic manufacturing flow of the printed circuit board.

In FIG. 3, a negative film is printed on a copper-clad epoxy printed board (both sides) 9 and then etched to create an intermediate layer having a wiring pattern 10.

In FIG. 3, several layers of the above-mentioned intermediate layers are stacked up, and an epoxy adhesive 11 (for example, glass cloth impregnated with epoxy resin) is placed between them and hot pressed to form a multilayer printed circuit board 4 ( Figure 3 2).

3. In FIG. 3, a hole 6 penetrating the multilayer printed circuit board 4 is drilled at a predetermined position.

4. In FIG. 4, a multilayer printed circuit board 4 having a through hole 6 is coated with a conductive layer, for example, copper plating 13, and the plating is thickened to form a blank through hole.

As a result, the inside of the hole and the outer surface of the multilayer printed circuit board are plated.

Further, in the through-hole of the Au plating resist, the inner wall of the hole 6 is thinly plated with gold as shown in FIG. 3, and a gold-plated pin 15' can also be press-fitted therein (FIG. 3, 5'').

At that time, the Meclastle Hole is no longer needed and the state shown in Fig. 3 6 will occur.

In FIG. 3, the surface layer is etched using a mask 14 in the necessary parts, and the copper plating 13 is removed by etching other parts to form a metal hole 15 (third
Figure 5 “).

In FIG. 3, a ceramic is plasma-sprayed, and the thickness of the ceramic is about 50 to 200 microns, and the ceramic coating 16 is covered over the metal hole 15.

FIG. 3 and 7 show surface polishing, in which the convex portions of the ceramic 16 are removed by polishing by rotating the grindstone of the polishing machine, and at this time, the surface is polished until the Cu surface of the Meclasp hole 15 is completely exposed.

This is to ensure a complete electrical connection with the metal that will be deposited next.

In FIG. 3, a metal film of tungsten, molybdenum, or the like as a base metal is formed on the upper surface of the ceramic 16 by sputtering to improve adhesion to the ceramic.

3. Next, a metal layer 8 (for example, A
etc.) is deposited to a thickness of several microns by electroplating or the like.

FIG. 3 10 A necessary surface pattern 1 is formed by coating the necessary portions with an etching mask 17 and then etching the surface layer.
8 (Fig. 3, 10').

The composite printed board of the present invention is produced through the above steps, but the steps 1 to 4 in FIG. 3 are exactly the same as the conventional method for manufacturing a resin multilayer printed board.

Therefore, the manufacturing method is stable.

Furthermore, considering the difference in thermal expansion coefficient between the resin laminate and ceramic, it is desirable to uniformly coat both sides of the circuit board with ceramic to balance external forces such as warping.

In addition, considering the heat resistance and adhesion of ceramic to the resin substrate,
Consideration must be given to adhesion, such as using a glass system with a low melting point and exposing the glass fibers on the attachment surface.

The present invention has been described above with reference to examples, but according to the present invention, after coating one or both sides of a resin multilayer printed board with ceramic, a metal adhesion layer is formed on the surface of the ceramic, and a conductive part connected to the metal is formed. By creating a structure in which the inner layer wiring patterns are drawn out, the heat resistance of the surface is improved, and the surface is smoother, allowing thin lines to be drawn, making it possible to increase pattern density.

Furthermore, by providing a ceramic layer on the surface, the surface became hard and TC bonding became possible, making it possible to package semiconductors at the chip level.

Furthermore, since both surfaces (or one side) of the resin multilayer board are coated with ceramic, it is possible to obtain a heat-resistant composite printed board that has the characteristics of a multilayer board with the inner layer made of resin, although the surface is a ceramic board.

As a result, thanks to the excellent heat resistance, hardness, and smoothness of ceramic printed boards, which have the good transmission characteristics and ease of manufacture of resin multilayer printed boards, it is possible to improve mounting density, which was not possible with conventional resin multilayer printed boards. The heat resistance has been improved, making it possible to perform die bonding of chips such as LSI, beam lead bonding, and TC bonding of wires.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional multilayer printed board. FIG. 2 is a cross-sectional view of the heat-resistant composite printed board of the present invention (before the surface pattern is created). FIG. 3 is an explanatory diagram showing a schematic manufacturing flow of the printed circuit board of the present invention. 1, 2, and 3 are inner layer wiring patterns, 4 is a resin multilayer printed board, 5 is a ceramic, 6 is a hole, 7 is a base metal, 8 is a metal layer, 9 is an epoxy printed board, 10 is a wiring pattern,
11 is an epoxy adhesive, 13 is copper plating, 14 is a mask, 15 is a mesh hole, 16 is a ceramic coating layer, 17 is an etching mask, 18 is a surface pattern, and 15' is a pin.

Claims (1)

[Claims] 1. After a ceramic is adhered to one or both sides of a resin multilayer printed board having a conductive part that leads an internal wiring pattern to the outside, a metal adhesion layer is formed on the surface of the ceramic, and the metal adhesion layer and the resin multilayer printed board are bonded. A heat-resistant composite printed board characterized in that a wiring pattern is drawn out through a conductive part provided protruding from the board.