JPH02172294A - Solder bonding method for electronic parts - Google Patents

Abstract

PURPOSE:To prevent short-circuitting caused by leaking-out of cream solder between adjacent lands by a method wherein cream solder is dispersed and printed so as to correspond with junction surfaces on a land, and the dispersed cream solder printing surfaces are arranged so as to be mutually connected by reflow soldering. CONSTITUTION:Cream solder 4 is dispersed and printed so as to correspond with junction surfaces on a land 3, and the dispersed cream solder printing surfaces are arranged so as to be mutually connected by reflow soldering. In this manner, the cream solder 4 is dispersed and mounted on the junction surfaces of terminal leads 6 of the land 3; by reflow soldering, the cream solder 4 is made to flow out; by the effect of surface tension, the solder stretches uniformly between the terminal Ieads 6 and the land 3, and connected, thereby performing solder bonding. Hence short-circuitting between adjacent lands 3 caused by leaking-out of cream solder can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a soldering joining method in which a plurality of terminal leads led out from the main body of an electronic component are soldered to lands formed on a printed wiring board by surface mounting. This is related to.

[Conventional technology]

Conventionally, a plurality of tangents v derived at equal intervals from the end face of the main body
When a flat package type electronic component 1 such as an integrated circuit is surface mounted on a printed wiring board 2 and joined by reflow soldering, the width of the terminal lead 6 and the pitch between each terminal lead are adjusted. A method is used in which lands 3 are formed on a printed wiring board, cream solder 4 is printed on the lands 3 using a printing mask 7 having openings 8 corresponding to the lands 3, and the lands 3 are joined by reflow soldering.

In this case, the width of the land 3 is made sufficiently larger than the width of the terminal lead 6, and the cream solder 4 is usually printed using a solder printing mask 7 having an opening 8 slightly smaller than the width of the land 3. The cream solder 4 melted during soldering 1 is transmitted between the land 3 and the terminal lead 6 due to surface tension and is soldered uniformly. affordability was guaranteed.

In recent years, as integrated circuits have become more highly integrated, the number of terminals has increased,
The pitch in the terminal lead and the pitch between the leads are pinched, and the number of terminals in a Claude type electronic component is 100 pins, and the pitch in the terminal is 0.
．． 5n+m, the pitch between terminal leads was 0, and it was put into practical use until later, when it was 65mo+.

In this case, the width of the land 3 is set to be approximately the same as the width of the terminal lead 6, and as shown in FIGS. 4 and 5, the space between adjacent terminal leads is pinched and the molten cream solder 4 is pushed out Therefore, there are many cases where short circuits occur due to contact with adjacent terminal leads 6 or lands 3, and the inspection and correction work becomes an obstacle to production.

[Problem to be solved by the invention]

The present invention has been made in view of the problems of the prior art described above, and it is an object of the present invention to provide a soldering method capable of eliminating short circuits caused by leakage of cream solder between adjacent lands 3.

[Means for solving the problem] In order to achieve the above object, in the present invention, cream solder is distributed and printed corresponding to the bonding surface on the land 3, and the distributed cream solder printed surface is reflow soldered. They are arranged so that they are interconnected.

[Effect]

According to the above configuration, the cream solder 4 is dispersed and placed on the joint surface of the terminal lead 6 of the land 3, and by performing reflow soldering, the cream solder 4 flows out and the terminal lead 6 and the land 3 are bonded to each other due to surface tension. The solder joints are made by spreading uniformly between them and connecting them.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a situation in which a Claude type flat package electronic component 1 is mounted on a printed wiring board 2. As shown in FIG.

In the electronic component 1, a plurality of terminal leads 6 are led out from the main body, and the terminal leads 6 are bent into a gull wing shape so that the bonding surfaces of the terminal leads 6 are flush with each other.

A plurality of lands 3 are formed on the printed wiring board 2 in accordance with the bonding surface lO of the plurality of terminal leads 6.
A solder resist 9 is printed on the outer periphery except for the solder joints, and at the same time guide marks or guide bin holes (not shown) for positioning the printing mask 7 of the cream solder 4 are provided.

The printing mask 7 has a circular or elliptical opening 8 formed in the joint surface 10 to match the joint surface 10 of the terminal lead 6, and the opening 8 is connected to the land 3 by a guide mark or a guide bottle hole of the printed wiring board 2. Aligned on and near the top.

Cream solder 4 is placed on land 3 from above printing mask 7 through opening 8 using a squeegee.

The printing mask 7 is removed, the flat package type electronic component 1 is aligned and mounted on the printed cream solder 4, and solder joint is performed by reflow soldering.

At this time, the dispersed cream solder printed surfaces are interconnected by the melted cream solder 4 and uniformly spread over the joint surface 10 to form a stable solder joint.

FIG. 2 is a partially omitted plan view showing details of the present invention, showing the arrangement pattern of openings 8 formed in the printing mask 6 and the printing pattern of the cream solder 4 printed on the lands 3.

Figure 2 (a) shows cream solder 4 on printed wiring board 2.
In the printed state, the cream solder 4 is distributed and printed in two places, and the outer periphery of the land 3 except for the solder joint part is covered with a solder resist 9.

FIG. 2(b) shows a state where the terminal lead 6 is soldered and the cream solder 4 melts and flows due to surface tension.
The margin portion 5 is filled and the terminal lead 6 and the land 3 are uniformly bonded.

FIG. 3 shows another embodiment of the present invention, in which an opening 8 having an inner diameter through which a certain amount of cream solder 4 passes is formed in a predetermined position of a printing mask 6 corresponding to a land 3, so that an appropriate amount of cream solder 4 can be applied. A plurality of cream solders 4 are uniformly formed on the solder joints of the lands 3.

According to the present invention, when the land 3 has a wide width, the openings 8 are appropriately selected and arranged in the cream solder printed surface in the terminal lead 5 and in accordance with the width of the land 3. It is also possible to load a uniform amount of ream solder.

〔Effect of the invention〕

Since the present invention is configured as described above, during reflow soldering, the molten cream solder 4 spreads from the cream solder printed surface onto the lands 3 to form a uniform solder layer, and is localized unlike the conventional example. It was possible to prevent an accident in which the melted cream solder 4 leaked out and caused a short circuit with the adjacent land 3 or terminal lead 6.

Furthermore, by forming circular or oval openings 8 in the printing mask 7 when printing cream solder, it becomes easier for the cream solder to pass through and prevent it from adhering to the printing mask 7. It was possible to prevent the printing from fading and shifting, and it was also possible to perform operations such as cleaning the printing mask 7 easily, thereby improving workability.

[Brief explanation of the drawing]

FIG. 1 shows the mounting of a flat package type electronic component on a printed wiring board, and FIG. Partial plan view showing the printed pattern, 3rd
The figure is a partially omitted perspective view showing another embodiment of the present invention, and FIGS. 4 and 5 are a partial plan view and a sectional view taken along the line A-A of the conventional example. In the figure, l is an electronic component, 2 is a printed wiring board, 3 is a land, 4 is cream solder, 5 is the same margin, 6 is a terminal lead, 7 is a printing mask, 8 is an opening, 9 is a solder resist,
10 is a joint surface. Patent applicant: Fujitsu General Ltd. Figure 2 Figure 4, Figure 5

Claims (1)

[Claims] In a soldering method in which cream solder is printed on a plurality of lands formed on a printed wiring board corresponding to a plurality of terminal leads leading out from the main body of an electronic component, and the solder is bonded by reflow soldering, A method for soldering and joining electronic components, in which cream solder is distributed and printed in correspondence with the joining surfaces, and the distributed cream solder printed surfaces are arranged so as to be interconnected by reflow soldering.