JPH01236693A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To enable an inner side of a printed wiring board to be retained at a low temperature by a method wherein two or more printed wiring boards, on which electronic components are mounted, are subjected to a vapor phase heat soldering treatment interposing intermediaries between them. CONSTITUTION:First, an adhesive resin layer 5 is made to adhere Mo an inside face of one of boards, for instance, a second printed wiring board 2, and the inside face of a first wiring board 1 is made also to adhere thereto through the intermediary of the adhesive resin layer 5 before surface mounting type electronic components 8 are joined to the outer faces of the first and the second printed wiring boards 1 and 2 through soldering. The boards 1 and 2 are made to adhere to each other or bond together, and then soldering pastes 9 are printed on surface conductors 3 and 4 and the surface mounting electronic components 8 are mounted thereon, which is placed in a vapor phase reflow device to be subjected to a vapor phase heat soldering process. By these processes, a soldering treatment can be performed under such a condition that a thermal effect on the previously mounted electronic components can be substantially ignored.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method of manufacturing a printed wiring board used in electronic equipment, and in particular, after forming two double-sided printed boards into a multilayer, reflow soldering is applied to both outermost surfaces. The present invention relates to a hybrid circuit board that forms a surface-mounted component using a mounting method.

Conventional Technology Conventionally, composite hybrid circuit boards have existed in which ceramic boards are bonded to ceramic boards, glass epoxy boards are bonded to polyimide, and the like. However, when reflow soldering of surface-mounted components is performed after bonding, the mutually bonded parts are heated together, and the bonding function is lost or significantly impaired.

Problems to be Solved by the Invention An object of the present invention is to first mount another electronic component on the other side of a printed wiring board with electronic components mounted on one side. An object of the present invention is to provide a means for efficiently performing soldering processing under conditions where the thermal influence on electronic components can be substantially ignored.

Means for Solving the Problems The present invention involves stacking a plurality of printed wiring boards with removable inclusions in between, and applying vapor phase heat soldering to both upper and lower surfaces of the outermost part of the printed wiring boards. It is used to process processes. At this time, the process of the present invention can be carried out suitably by using a removable adhesive resin as the inclusion.

According to the present invention, when a plurality of printed wiring boards on which electronic components are mounted are placed facing each other and subjected to a vapor phase heating soldering process with inclusions sandwiched between them, the soldering process is performed in advance by sealing the printed wiring boards with the inclusions. The temperature rise on the heated surface can be suppressed, and even when the outermost surface reaches the desired heating temperature, the temperature on the inner surface of the printed wiring board can be maintained at a considerably low temperature.

Embodiment In the present invention, the following measures are taken to improve the condition of the bonded portion, which has low solder heat resistance. That is, the holes or through-hole connection holes in the wiring boards to be bonded are closed in advance with organic resin or inorganic cement that has low thermal conductivity. Thereafter, the entire surface is bonded using an adhesive layer such as epoxy resin or polyester resin.

At this time, for the opposing through-hole plated parts that require electrical connection as mutual wiring boards,
The solder paste is printed, and reflow soldering is performed at 215° C. for 30 seconds using an infrared heat source, in combination with the resin thermosetting bonding step, using vertical heating, that is, double-sided heating from the top and bottom. The bonded portion of the integrated circuit board is thus prevented from causing convection with outside air or breathing action of air.

Next, the entire composite board is made into one sheet, and solder paste is printed on one or both sides of the composite board and surface-mounted parts are mounted.

When this composite plate is placed in a paper phase tank, condensation of Freon solvent vapor occurs on one or both sides, but not on the adhesive side. Therefore, when the outer surface is at 215°C, the adhesive surface can be kept at 150°C or lower.

Therefore, the adhesive surface is a homogeneous binder (melting point of 183° C.).

Even if a resin with a heat softening temperature of 160° C. is used, there is no risk of the composite bonding part being destroyed or the adhesive strength decreasing, so a low-cost and highly versatile adhesive material can be used.

Next, specific examples will be described with reference to the drawings.

The drawings are developed cross-sectional views of main process parts for explaining embodiments of the present invention. The first printed wiring board 1 has a wiring layer 3 made of copper foil formed on both sides thereof in a predetermined pattern.
A tin-lead based solder paste 9 is adhered to the wiring layer 3 on one side. And this solder paste 9
is for soldering the surface-mounted electronic component 8 at its end electrode portion. Further, this printed wiring board l is made of a glass cloth base resin substrate with a thickness of 1.0 mm, for example, and has a diameter of about 0.0 mm with respect to the wiring layers 3 on both sides.
A 6 mm hole, a so-called through hole, is formed, and this through hole is filled with a conductive material such as conductive paint when a double-sided wiring layer connection is required, and with resin paint when a conductive connection is not required. filler 6 each
Close as. The second printed wiring board 2 has the same structure as the first printed wiring board 1, except that the solder layer 7 is formed on the necessary parts of the inner surface, and the wiring layer 4 is also the same as the wiring layer 3. are used.

Prior to joining the surface-mounted electronic components 8 to the outer surfaces of the first printed wiring board 1 and the second printed wiring board 2 by soldering, first, one of the wiring boards, for example, the second printed wiring board An adhesive resin layer 5 is attached to the inner surface of the plate 2. Then, the inner surface of the first printed wiring board 1 is attached to the adhesive resin layer 5 as an intervening material. The adhesive resin layer 5 is made of, for example, a solvent-free epoxy resin that is completely cured or temporarily cured by a curing treatment at 150° C. or lower.

After adhesion or adhesion of both front plates, a tin-lead 60-40 solder paste 9 is printed on the surface conductor 3.4 and a surface mounting component 8 is placed. A separate adhesive is also used for the bottom surface. The thus obtained composite wiring board was placed in a 70 linate paper phase (vapor phase) reflow apparatus for 30 seconds.

The surface reaches the conditions for reflow soldering at a temperature of 215°C, but the adhesive or bonding surface remains at a temperature increase of 105°C because there is no condensation of Fluorinert vapor. Therefore, softening of the resin and melting of the solder on the adhesive surface do not occur. In addition,
If the surface is dip-soldered, the soldering of surface-mounted parts will only be attached to the outer surface, which cannot be soldered.

Effects of the Invention As described above, according to the present invention, two wiring boards can be bonded together using commercially available materials and then subjected to reflow soldering, and can be used as a pseudo electrical layer wiring board. To obtain a composite wiring board with high density and short wiring paths.

[Brief explanation of the drawing]

The drawing is a developed cross-sectional view of a printed wiring board used in an embodiment of the present invention. 1.2...Printed wiring board, 3,4...
・Wiring layer, 5... Adhesive resin, 6...
Filler, 7...Solder layer, 8...Electronic component, 9...Solder paste. Name of agent: Patent attorney Toshio Nakao and 1 other person/--Issai 1 l ('Sen version 2-f2fL's version J-Iichi Kasumi 1 4--Issuance 1 5-Shimotsuki Ucho 6-a Shield filling goods q ---1, J tJ8 to Relationship with Patent application
Appointment Address: 1006 Kadoma, Kadoma City, Osaka Prefecture
Name (582) Matsushita Electric Industrial Co., Ltd. Representative Akio Tanii 4 Agent Address 7, Matsushita Electric Industrial Co., Ltd. 1006 Oaza Kadoma, Kadoma rlr, Osaka Prefecture Contents of amendment (1) Specification page 7 Change “Drawing” in line 10 to “Figure 1”
will be corrected. @) Correct the drawing as shown in the attached sheet.

Claims (2)

[Claims] (1) A plurality of printed wiring boards are stacked with removable inclusions in between, and both upper and lower surfaces of the outermost part of the printed wiring boards are subjected to a vapor phase heating soldering process. A method for manufacturing printed wiring boards. (2) The method for manufacturing a printed wiring board according to claim 1, wherein the inclusion is composed of an adhesive resin layer.