JP3239483B2 - Electronic component soldering method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of soldering an electronic component to an electrode of a substrate.

[0002]

2. Description of the Related Art Soldering for mounting electronic components such as a capacitor chip, a resistor chip, and a chip with leads on a substrate is performed by first forming a solder portion on an electrode portion of the substrate and then mounting the electronic component on the solder portion. After the electrodes are landed and mounted, the substrate is sent to a heating furnace, the substrate is heated above the melting temperature of the solder to melt the solder, and then the molten solder is cooled and solidified.

In this case, the electronic component is temporarily fixed to the substrate by a temporary fixing bond so that the position of the electronic component is not shifted until the solder is solidified and the electronic component is securely soldered to the substrate. Is Hereinafter, FIG.
A conventional method for soldering electronic components will be described with reference to FIG.

In FIG. 3A, a cream solder 3 as a solder portion is applied on an electrode portion 2 formed of copper foil on the surface of a substrate 1. As shown in FIG. 4, the cream solder 3 is an aggregate of fine solder particles, and is generally applied onto the electrode unit 2 by a screen printing device.

Next, as shown in FIG. 3B, a temporary bonding bond 4 is applied to the upper surface of the substrate 1. This temporary fixing bond 4 is applied by a bond application device such as a dispenser. Next, as shown in FIG. 3C, the electronic component 5 is mounted by a chip mounter. The electronic component 5 of the present embodiment is a leaded electronic component, and is provided with an electrode 7 from the side of the main body 6.
The main body 6 is landed on the temporary fixing bond 4, and the electrode 7 is landed on the cream solder 3.

Next, the substrate 1 is sent to a heating furnace, and the substrate 1 is heated to a temperature higher than the melting temperature of the cream solder 3 (generally, about 183 ° C.). Then, when the cream solder 3 is melted and then the substrate 1 is cooled, the melted cream solder 3 is solidified and the electrodes 7 of the electronic component 5 are soldered to the electrode portions 2 of the substrate 1 (FIG. 3D). . The temporary bond 4 is a thermosetting synthetic resin. When the substrate 1 is heated, the temporary bond 4 is cured, and the main body 6 of the electronic component 5 is fixed to the substrate 1.

[0007]

The above-mentioned temporary fixing bond 4 is generally formed by mixing a curing agent with a synthetic resin such as an epoxy resin, and its curing temperature is about 150 ° C. It is considerably lower than the melting temperature of the solder (generally about 183 ° C. as described above). Therefore, when the substrate 1 is heated in a heating furnace, the cream solder 3 is melted after the temporary bonding bond 4 is hardened. Further, as described above, since the cream solder 3 is an aggregate of fine solder particles, the material thereof is considerably sparse and has many voids. Therefore, when heated and melted, the volume thereof is considerably reduced.

As described above, the temporary fixing bond 4 is first cured before the cream solder 3 is melted. Therefore, when the cream solder 3 is melted, the electronic component 5 weighs itself or the surface tension of the melted cream solder 3. Is hindered by the cured temporary bonding bond, and as a result, the distance h between the upper surface of the substrate 1 and the lower surface of the electronic component 5 becomes considerably large, and on the other hand, as described above, the cream solder 3 Since the volume of the solder 3 is considerably reduced upon melting, the cream solder 3 obtained by melting and solidifying the solder 3 on the left side of FIG. 3D as shown in a partially enlarged view of FIG. In the worst case, there is a problem in that the solder 7 on the right side of FIG. 3D is lifted from the melted and solidified solder 3 as shown in a partially enlarged view of FIG.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for soldering an electronic component, which can solve the above-mentioned problems of the conventional means and can firmly solder an electrode of the electronic component to an electrode portion of a substrate.

[0010]

In order to achieve this, the present invention provides a process of forming a solder precoat portion having a flat surface on an electrode portion formed on the surface of a substrate, and applying a flux to the upper surface of the solder precoat portion. A process of applying a temporary bonding bond whose curing temperature is lower than the melting temperature of the solder precoat portion on the upper surface of the substrate, landing an electrode on the flux, and attaching the main body to the temporary bonding bond. A process of landing and mounting the electronic component on the substrate, and heating the substrate to cure the temporary bonding bond, melt the solder pre-coated portion, and apply a surface tension to the central portion of the electrode portion. smell
Constitute a soldering method of the electronic component to the electronic component electrode by ascended prime from the process to be soldered to the conductive <br/> pole portion of the substrate Te.

[0011]

According to the above construction, since the material of the solder pre-coated portion is dense, even if the material is heated and melted, the volume of the solder pre-coated portion hardly decreases, and furthermore, the surface tension causes the electrode portion to be hardened.
The electrode of the electronic component can be firmly soldered to the electrode portion of the substrate because the electrode swells at the center of the substrate.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIGS. 1A to 1E show a process of soldering an electronic component to a substrate. In FIG. 1A, an electrode portion 2 is formed on the upper surface of a substrate 1, and a solder precoat portion 8 is formed on the electrode portion 2. The solder precoat portion 8 is formed by plating means or leveler means, and has a flat surface and a dense material.

Next, as shown in FIG. 1B, a flux 9 is applied on the solder pre-coat portion 8. This flux 9
Is applied by a dispenser or a screen printing device. Next, as shown in FIG. 1C, a temporary bonding bond 4 is applied on the upper surface of the substrate 1, and then the electronic component 5 is mounted as shown in FIG. 1D. In this case, the electrode 7 of the electronic component 5
Is landed on the flux 9, and the main body 6 is landed on the temporary fixing bond 4. The temporary fixing bond 4 may be applied before the flux 9 is applied, and the application timing is not limited to this embodiment.

Next, the substrate 1 is sent to a heating furnace, and the substrate 1 is heated to a temperature equal to or higher than the melting temperature of the solder precoat 8 (generally 183 ° C.). Then, the solder precoat 8 melts, and when the substrate 1 is cooled next, the melted solder precoat 8 solidifies,
The electrodes 7 of the electronic component 5 are soldered to the electrode portions 2 of the substrate 1 (see FIG. 1E).

The temporary bonding bond 4 is a thermosetting synthetic resin which is cured at about 150 ° C., and is cured before the solder precoat portion 8 is melted to fix the main body 6 to the substrate 1. Although the solder pre-coat portion 8 is melted after the temporary fixing bond 4 is hardened, the material is dense, so that even if the solder pre-coat portion 8 is melted, the volume hardly decreases, and as shown in FIG.
The electrode 7 is firmly soldered to the electrode portion 2 of the substrate 1.

As shown in FIG. 2A, even when the electrode 7 of the electronic component 5 mounted on the substrate 1 is lifted from the solder precoat portion 8 having a flat surface, as shown in FIG. When the solder precoat portion 8 is melted, it gathers at the center of the electrode portion 2 due to its surface tension and swells, so that the floating electrode 7 is also securely soldered.

[0018]

As described above, according to the method for soldering electronic components according to the present invention, since the material of the solder precoat portion is dense, the solder precoat portion is melted after the temporary fixing bond is cured. However, the volume hardly decreases,
The electrodes of the electronic component can be firmly soldered to the electrodes of the substrate. Also, even when the electrodes of the electronic component are floating from the solder pre-coat portion, the molten solder pre-coat portion gathers at the center of the electrode portion due to surface tension and swells,
Floating electrodes can be soldered firmly.

[Brief description of the drawings]

FIG. 1A is a perspective view of a substrate according to an embodiment of the present invention. FIG. 1B is a cross-sectional view of the substrate according to an embodiment of the present invention. (D) Cross-sectional view of board on which electronic component of one embodiment of the present invention is mounted (e) Cross-sectional view of board after soldering of electronic component of one embodiment of the present invention

FIG. 2A is a partial cross-sectional view of one embodiment of the present invention before solder is melted. FIG. 2B is a partial cross-sectional view of one embodiment of the present invention after melting solder.

3A is a perspective view of a conventional substrate. FIG. 3B is a cross-sectional view of a conventional substrate after a bond is applied. FIG. 3C is a cross-sectional view of a substrate on which conventional electronic components are mounted. Cross section of the board after mounting

FIG. 4 is an enlarged view of a conventional cream solder.

FIG. 5 is an enlarged view of a main part after conventional soldering.

FIG. 6 is an enlarged view of a main part after conventional soldering.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode part 4 Temporary bond 5 Electronic component 6 Main body part 7 Electrode 8 Solder precoat part 9 Flux

Claims (1)

(57) [Claims] An electrode formed on a surface of a substrate has a flat surface.
Applying a process of forming a tongue solder precoating unit, and process for applying flux to the upper surface of the solder precoat portion, the cure temperature on the upper surface of the substrate is a temporary fastening bond below the melting temperature of the solder precoat portion A process of mounting an electronic component on the substrate by landing an electrode on the flux and landing a main body on the temporary fixing bond; and curing the temporary fixing bond by heating the substrate. While melting the solder pre-coated portion ,
Due to the surface tension, it rises at the center of the electrode
Soldering method of the electronic component, which comprises a process of racemate Te soldering electrodes of the electronic component on the electrode portion of the substrate.