JPS60211997A - Method of soldering both-side 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 method for soldering a double-sided circuit board, and particularly to a soldering method suitable for soldering surface-mounted components on both sides of a board simultaneously on both sides by one method. Regarding the method.

[Background of the invention]

Among the methods of soldering so-called surface-mounted components on both sides of a circuit board, conventional methods have been to use circles printed with solder and paste on both sides of the circuit board to minimize the soldering heat stress applied to the surface-mounted components. There is a method for reflow soldering by mounting surface-mounted parts and feeding the board almost horizontally onto the mesh belt of an infrared ray irradiation conveyor furnace. The problem is that surface-mounted components mounted on the bottom surface of a circuit board that is attached to the circuit board fall off due to the weight load exceeding the adhesive strength of the solder paste. To provide a method for soldering a double-sided circuit board without parts falling off and with little soldering heat stress applied to the parts.

[Summary of the invention]

In order to minimize soldering heat stress, we adopted a single flow soldering method for both sides simultaneously using solder paste and an infrared irradiation conveyor furnace.

In order to avoid components falling off, a thermosetting adhesive is interposed between the components and the circuit board, and the adhesiveness of the thermosetting liquid adhesive is utilized to prevent components from falling off.

[Embodiments of the invention]

The F1 invention will now be explained with reference to the drawings.

FIG. 1 is a process flowchart of the present invention, and FIG. 2 is a sectional view of essential parts of a double-sided circuit board corresponding to FIG. 1.

In the present invention, a solderable conductor 2 is formed on both sides of an insulating ceramic substrate 1 by printing and baking means, vapor deposition, plating, etc., and if necessary, a resistor (not shown) is formed.
After forming the insulating solder resist 3 by printing and baking means or vapor deposition, solder powder, rosin, etc. are simultaneously or separately applied to both surfaces A and B of the double-sided circuit board formed by printing and baking the insulating solder resist 3. Solder paste 4f made by kneading flux and solvent. : After applying to the desired pattern shape to a film thickness of 200 to 400 μm, place the solder paste on the A side at the part where the surface-mounted component 6 will be mounted, with the A side facing up and holding the solder paste on the B side so as not to damage it. , and where there is no pattern of solder paste 4, apply 20I
A thermosetting material that has the property of curing under flow conditions with a temperature peak of fC to 30D'C, has viscosity in the temperature and time range from 10°C to curing, and has insulation properties. Adhesive 5 (for example, Bostic Japan (
(Liquid-based epoxy adhesive BosTiK≠3590)
'i After applying with a dispenser or the like, the surface-mounted part 6 is mounted. Next, flip the circuit board over, with the B side facing up so as not to touch the parts mounted and attached to the A side.
After holding the circuit board and mounting the surface-mounted part 6', the size of this form is supplied onto a mesh belt of an infrared ray irradiation type conveyor furnace and subjected to reflow conditions having a temperature peak of 200°C to 600°C. A double-sided circuit board is formed by solder reflow.

According to this embodiment, the surface-mounted component 6 attached to the lower surface A during solder reflow is held on the board surface by the adhesiveness of the thermosetting adhesive 5, so there is no fear that it will come off and fall. This has the effect of making it possible to solder double-sided circuit boards with high yield.

〔Effect of the invention〕

According to the present invention, double-sided circuit boards can be soldered at a high yield without causing expensive surface-mounted components to fall off or be damaged, so it is possible to economically produce double-sided circuit boards with high packaging density.

Further, as long as the ceramic substrate in the above embodiment is an insulating substrate, this effect will not be hindered, and it goes without saying that a resin substrate such as an epoxy substrate containing glass fiber may also be used.

[Brief explanation of the drawing]

Fig. 1 is a process flow chart of the soldering method of the present invention, and Fig. 2 is a process flow chart of the soldering method of the present invention.
FIG. 2 is a cross-sectional view of essential parts of an embodiment of the double-sided circuit board according to the present invention, corresponding to FIG. 1; DESCRIPTION OF SYMBOLS 1... Ceramic board, 2... Conductor, 5... Solder resist, 4... Solder paste, 5... Thermosetting adhesive , 6.6′... Surface mounted parts. E 1 Illustration Z diagram

Claims (1)

[Claims] Apply solder paste to the desired areas on both sides of the circuit board that has soldering electrodes on both sides, and apply thermosetting and adhesive to the parts of both sides or one side where solder paste is not applied and where the components will be mounted. After applying the adhesive and mounting the components on both sides of the circuit board, the solder paste is applied by heating means, and at the same time, the adhesive is cured to solder and connect the components to both sides of the circuit board. A soldering method for double-sided circuit boards that features: