JPH0818219A - Method for mounting electronic component - Google Patents

Abstract

PURPOSE:To eliminate connection defects due to a fine lead pitch and improve the accuracy of solder connection at a high temperature. CONSTITUTION:The land 3 on a substrate 1 is coated with flux 2b and an electronic component is mounted by permitting the lead 5 of the electronic component 4 to be on the land 3. Then, a molten solder supply jig 6a, which is provided with a molten solder discharging port 7 which corresponds to the lead 5 of the electronic component 4, is brought down, molten solder 8b is dripped on each lead 5 of the electronic component 4 and the lead 5 and the land 3 are connected by solder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting method for electronic parts, and more particularly to a mounting method for surface mounting electronic parts.

[0002]

2. Description of the Related Art In the conventional mounting method of electronic parts, various jigs are devised when the pitch of leads is made fine or when a high temperature reflow furnace is used.

FIGS. 3 (a) to 3 (c) are cross-sectional views of an electronic component and a solder connection jig shown in the order of steps for explaining an example of the related art. First, as shown in FIG.
A metal mask 12 is placed on the printed board 1, and the cream solder 10a is printed as a solder 10b on each land 3 using a squeegee 11. Then, FIG.
As shown in (b), the semiconductor package 4 is mounted so that the leads 5 are placed on the printed solder 10b. After that, as shown in FIG. 3C, the cream solder 10b is heated and melted using a reflow furnace. Thereby, the leads 5 of the semiconductor package 4 and the lands 3 of the substrate 1 are connected like solder 9.

[0004]

In the conventional method of mounting electronic components described above, it becomes difficult to print lead solder with a predetermined accuracy as the pitch of the leads becomes finer, and adjacent leads are connected and short-circuited. Bad or
There is a drawback that a connection failure due to insufficient solder between the land and the lead is likely to occur. In particular, when the lead pitch is less than 0.3 mm, it is difficult to print cream solder.

In the conventional mounting method of electronic parts, the board is heated too much by passing through a reflow furnace and is greatly warped. There is a disadvantage that solder connection failure between the leads is likely to occur.

An object of the present invention is to provide a mounting method of an electronic component which eliminates such a short between leads and a poor connection between a land and a lead.

[0007]

According to a method of mounting an electronic component of the present invention, the electronic component is mounted on the substrate so that the lead of the electronic component is mounted on a land formed on the substrate, and then each of the leads is mounted. A molten solder supply jig having a plurality of corresponding ejection ports is moved onto the electronic component, and the ejection ports and the leads are aligned so as to correspond to each other, and then the land or the leads are placed. It is configured to discharge molten solder from the molten solder supply jig to connect the land and the lead by soldering.

Further, in the method of mounting electronic components of the present invention, heating the land of the substrate and the leads of the electronic components by blowing a heating gas before or during the ejection of the molten solder is effective for stable solder connection. It is effective, and after applying flux onto the land of the board using a flux supply jig that has multiple discharge ports corresponding to each land, mounting the electronic parts on the board ensures more reliable solder connection. It will be possible.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. 1A to 1E are cross-sectional views of an electronic component and a flux or solder supply jig, which are shown in the order of steps for explaining an embodiment of the present invention. First, FIG.
As shown in (a), in this embodiment, the flux 2b is applied onto the lands 3 of the printed circuit board 1 by using the flux supply jig 13 having the discharge ports corresponding to these lands 3 and filled with the flux 2a. To do. Next, as shown in FIG. 1B, the semiconductor package 4 is mounted on the printed board 1 so that the leads 5 of the semiconductor package 4 as an electronic component are mounted on the lands 3 of the printed board 1.

Next, as shown in FIG. 1C, after the printed board 1 is preheated through an infrared heating furnace, a plurality of ejection openings 7 corresponding to the leads 5 of the semiconductor package 4 are provided and molten solder is used. The molten solder supply jig 6a filled with 8a is moved onto the semiconductor package 4, and the ejection port 7 and the lead 5 are positioned so as to correspond to each other. Further, as shown in FIG. 1 (d), the molten solder 8b is supplied from the molten solder supply jig 6a onto the land 3 or the lead 5,
In particular, the liquid is discharged onto the tip of each lead 5 of the semiconductor package 4. Thereafter, as shown in FIG.
The land 3 and the lead 5 are connected by the solder 9 by removing the molten solder supply jig 6 a and gradually cooling it.

Here, the preheating is performed by preliminarily warming the lead 5 and the land 3 of the solder connection portion,
This is necessary to prevent the b from rapidly cooling and solidifying when b is discharged, and to obtain good solder wetting. On the other hand, the discharged molten solder 8a is heated and melted in advance in the molten solder supply jig 6a. That is, by controlling the gas pressure in the molten solder supply jig 6a and applying a predetermined pressure to the solder liquid surface for a certain period of time, an appropriate amount of molten solder 8b
Enables the supply of. Further, in the case where the position where the molten solder 8a is discharged is the upper part of the lead 5, the solder is lumped and easily adheres to the upper part of the lead, which causes a short circuit between the leads and a connection failure between the land and the lead. On the land near the tip of the lead 5 or near the tip of the lead 5.

Further, in order to obtain a stable amount of solder to be discharged, the soldering is preferably performed in an inert gas atmosphere such as nitrogen. In this case, it is possible to suppress variations in the discharge amount due to the surface of the molten solder being oxidized and the viscosity being increased.

According to this embodiment, it is possible to individually supply a very small amount of solder to each lead.
It is possible to perform solder connection of electronic components having a fine lead pitch. Moreover, the heated parts are only the electronic parts and the land parts to be connected, the influence of the warp of the printed circuit board is small, and the electronic parts already mounted are not thermally damaged.

FIG. 2 is a sectional view of an electronic component and a molten solder supply jig for explaining another embodiment of the present invention. Figure 2
In this embodiment, the flux applying step is omitted and only the molten solder is ejected. In mounting such electronic components, the printed circuit board 1
The flux 2b is applied on the land 3 of the
After the molten solder supply jig 6b satisfying the condition (a) is aligned on the lead 5 of the semiconductor package 4, the molten solder 8b
The heated nitrogen gas is blown from above the semiconductor package 4 before and during the ejection. This nitrogen gas is introduced from a nitrogen gas introduction pipe 14 provided in the molten solder supply jig 6b, and is blown from a nitrogen gas ejection port 15. In this case, since the lands 3 and the leads 5 of the semiconductor package 4 are sufficiently heated, the wettability of the discharged molten solder 8b to the lands 3 and the leads 5 is further improved. Further, since the molten solder 8b, the lands 3, and the leads 5 are in a nitrogen atmosphere, there is little oxidation due to heating. Therefore, in this embodiment, the discharge amount of the solder 8b is more stable and the wetting and spreading of the solder on the lands 3 and the leads 5 is better than that of the above-described embodiment, so that good soldering can be performed and the soldering time can be improved. Can also be short.

The above two embodiments have been described. As to the method of supplying the flux, in addition to the method of the above-described embodiment, a single-coating method using a dispenser having a single discharge port, a method of spraying, and the like. It may be applied to the entire surface of the substrate by a method or the like. Also, the land of the printed circuit board is depressed with respect to the surface of the board, so that the mounted electronic components are less likely to be displaced. When the land is not concave, the material of the flux is desirably high in adhesiveness so that the mounted electronic components do not shift during transportation or the like.

[0016]

As described above, the method for mounting electronic components of the present invention discharges molten solder corresponding to each lead, which is advantageous for making fine pitches and less likely to cause a connection between solders. Moreover, since a stable amount of solder can be obtained, it is possible to reduce the connection failure between the substrate and the electronic component. Further, according to the present invention, since the heated portion is only the connected electronic component and the land, there is an effect that the connection failure due to the warp of the substrate and the thermal damage to the component already mounted are not caused.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electronic component, a flux, and a solder supply jig, which are shown in the order of steps for explaining an embodiment of the present invention.

FIG. 2 is a sectional view of an electronic component and a solder supply jig for explaining another embodiment of the present invention.

FIG. 3 is a cross-sectional view of an electronic component and a solder connecting jig shown in the order of steps for explaining a conventional example.

[Explanation of symbols]

 1 Substrate 2a, 2b Flux 3 Land 4 Semiconductor Package 5 Leads 6a, 6b Molten Solder Supply Jig 7 Molten Solder Discharge Port 8a, 8b Molten Solder 9 Solder 13 Flux Supply Jig 14 Nitrogen Gas Inlet Pipe 15 Nitrogen Gas Jet

Claims (5)

[Claims] 1. A molten solder supply jig having the electronic component mounted on the substrate such that the lead of the electronic component is mounted on a land formed on the substrate, and then having a plurality of ejection openings corresponding to each of the leads. While aligning the discharge port and the lead so as to correspond to each other by moving the above-mentioned electronic component, and then discharging the molten solder from the molten solder supply jig onto the land or the lead, and A method for mounting an electronic component, characterized in that a land and the lead are connected by soldering. 2. The electronic component mounting method according to claim 1, wherein a heating gas is ejected before or during the ejection of the molten solder. 3. The electronic component according to claim 1, wherein the molten solder supply jig is provided with a nitrogen gas ejection port near the ejection port, and ejects high-temperature nitrogen gas before or during the ejection of the molten solder. How to implement. 4. A step of applying a flux from a flux supplying jig onto a land formed on a substrate, a step of mounting the electronic component so that a lead of the electronic component is placed on the land, and each of the leads. A step of moving a molten solder supply jig having a plurality of corresponding solder ejection openings onto the electronic component and aligning the ejection openings and the leads so as to correspond to each other; A step of discharging molten solder from the molten solder supply jig to solder-connect the land and the lead. 5. The electronic component according to claim 4, wherein the molten solder supply jig has a nitrogen gas ejection port in the vicinity of the ejection port, and ejects high-temperature nitrogen gas before or during the ejection of the molten solder. How to implement.