JPS5857785A - Method of mounting electronic part - 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] The present invention is an electronic component mounting method in which several electronic components are attached to a small board to form blocks, and then these blocks and the small boards are attached to a large board to assemble various electrical devices. The purpose of this invention is to provide an excellent mounting method that can be easily and reliably implemented with a simple configuration.

BACKGROUND ART Recently, miniaturization of electronic devices has become active, and chip-shaped electronic components without leads are increasingly being used as various electronic components. Also, devices have been developed in which several of these electronic components are attached to a small board to form a block, thereby improving the ease of assembly as a whole.

However, with the devices developed so far, when a small board is soldered to a large board, various electronic components may fall off from the small board, which is extremely inconvenient.The present invention solves the above drawbacks of the conventional ones. /J-The melting point of the solder when mounting electronic components on a board is different from the melting point of the solder when attaching a small board to a large board, and when attaching a small board to a large board. It is designed to prevent any of the various electronic components from falling off the small board.

Hereinafter, the electronic component mounting method of the present invention will be explained with reference to drawings of one embodiment. The figure is a cross-sectional side view of a t″L mounting device assembled based on the electronic component mounting method of the present invention. In the figure, 1 is a large board made of an ordinary printed wiring board, etc.; The formed conductor layer 3 is a small substrate attached to the large substrate 1, 4 is a conductor layer formed on the small substrate 3 and made of silver, palladium alloy, etc., and 5 is a conductor layer that is mounted on the small substrate 3 and has no lead wire. Chip-shaped electronic component, 6 is electronic component 60
The electrodes 7 formed on both ends are made of copper 3 having a low melting point, for example, for soldering the conductor layer 4 of the small board 3 to the conductor layer 2 of the large board 1.
7%, tin 63% solder, 8 is a high melting point copper 9, for example, for soldering the electrode 6 of the electronic component 5 to the conductor layer 4 of the small board 3.
5% or more, solder with tin 5 or less], 9 and 10 are electronic components 5. Small board 3.Small board 3. Adhesive for temporarily fixing large board IK.

Note that it is desirable to use solder 8 having a high melting point that contains a small amount of silver, for example, about 1.6%.

By the way, in the above embodiment, each electronic component 5 is mounted on the large board 1 in the following order. First, adhesive 9 is applied to the small board 3 at position V, and the electronic component 6 is placed there and temporarily fixed. Then, after that, the melting point is changed to 36, for example.
01: Front and rear U-shaped copper 96.6%, tin 3.0%, silver 1.
The electrodes of the electronic component 6 are attached to the conductor layer 4 of the small substrate 3 for half a time using 6% potted In 8. In this case, it is also possible to use the immersion soldering method, but if the small board 3 has a very low VC, cream solder is used as the solder 8,
It is more desirable to attach a half-HJ using the reflow one-way type C'.

When attaching the small board 3 that has been made into blocks in this way to the large board 1Vr, first apply a temporary fixing suffix 10 to the required position of the large board 1, and then apply the adhesive 10 to the large board 1Vr. (Temporarily fix the small board 3 to the required position on the large board 1 using i7. Then, solder 7 of 37% copper and 63% tin, which has a low melting point, for example around 2500.
The conductor layer 4 formed on the small substrate 3 is attached to the conductor layer 2 formed on the large substrate 1 by a half-width using a. In this case, the large board 1 is composed of a normal printed wiring board, and therefore,
Soldering by dip soldering is advantageous in terms of workability and other aspects.

By the way, when soldering is carried out by the immersion soldering method, the solder 8 is also immersed in the molten solder T, but since the melting point of the solder 8 is higher than that of the solder 7, the solder 8 itself cannot be melted. Therefore, it is possible to completely prevent the electronic component 5 from falling off the small board 3. However, if silver-containing solder is used as the solder 8, even if the silver in the conductor layer 4 formed on the small substrate 3 and made of silver, palladium, etc. is scattered during soldering, it can be removed from the solder 8. It has the advantage that it can be fully replenished with silver. That is, if a silver-palladium alloy or the like is used as the conductor layer 4 formed on the small substrate 3, the heat will scatter the silver during half-EB bonding, and the conductivity will deteriorate significantly. When used, it can be replenished by the silver in the solder, which has the advantage of being extremely advantageous in practice.

As is clear from the examples above, the electronic component mounting method of the present invention involves attaching electronic components to a small board using solder with a high melting point, and then immersion soldering the small board using solder with a low melting point. According to the law, it can be mounted on a large board, so it is easy to install, and electronic components do not fall off from the small board even when a small board is mounted on a large board, making it extremely advantageous in practice. be.

[Brief explanation of drawings]

The figure is a cross-sectional side view of an embodiment of a mounting device assembled based on the electronic component mounting method of the present invention. 1. Large board, 3. Small board, 5.
, , , , ,Electronic components, 7 , 8 , , , , ,Solder.

Claims (3)

[Claims] (1) The electronic component is soldered to a small board using solder with a high melting point, and then the small board is soldered to a large board using a flat solder with a low melting point by immersion soldering. Electronic component mounting method. (2) The electronic component mounting method according to claim 1, characterized in that silver-containing solder is used as the solder having a high melting point. (3) The electronic component mounting method according to claim 1, wherein the difference in melting point between the high melting point solder and the low melting point solder is about 100° C. or more.