JPH02172293A - Solder bonding method for electronic parts - Google Patents

Abstract

PURPOSE:To prevent short-circuitting caused by leaking-out of cream solder between adjacent conductor pattern surfaces by a method wherein a blank space part where the cream solder is not printed is formed in a part of a section formed by dividing a land into a plurality of sections, the amount of cream solder is adjusted by the ratio of the area of a cream solder printing surface to the area of the blank space part, and solder bonding is performed. CONSTITUTION:A land 3 is divided into a plurality of sections; a blank space part 5 where cream solder is not printed is formed in a part of the section; by the ratio of the area of a cream solder printing surface 3a to the area of the blank space part 5, the amount of cream solder 4 is adjusted, and solder bondig is performed. In this manner, a part of the land 3 is divided: the blank space part 5 for the cream solder 4 is formed on the bonding surface of a terminal lead 6; the cream solder 4 is printed by being divided into a plurality of surfaces; by reflow soldering, the cream solder 4 is uniformly dispersed over the bonding surface between the land 3 and the terminal lead 6 containing the blank space part 5. Thereby, the leaking-out of the cream solder 4 and the short-circuitting between adjacent conductor patterns 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. It is related to.

[Conventional technology]

Conventionally, a flat package type electronic component 1 such as an integrated circuit, which has a plurality of connection terminals led out from an end surface of a main body at equal intervals, is surface mounted on a printed wiring board 2 and joined by reflow soldering. , a land 3 is formed on the printed wiring board according to the width of the terminal lead 6 and the pitch between each terminal lead, and an opening 8 corresponding to the land 3 is formed.
A method is used in which the cream solder 4 is printed on the land 3 using a printing mask 7 having a 100% density, and the solder is bonded 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 is transmitted between the land 3 and the terminal lead 6 due to surface tension, and is soldered uniformly, and the excess ream solder 4 spreads over the land 3 and forms a fillet, resulting in reliable soldering. sex was guaranteed.

In recent years, as integrated circuits have become more highly integrated, the number of terminals has increased,
The terminal lead width and the pitch between the leads are pinched, and the number of terminals is 100 in a Claude type electronic component, and the terminal inside is 0.
．． 5 mm, and those with a pitch between terminal leads of 0.65 mm have been put into practical use.

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. 5 and 6,
There are many cases where the gap between adjacent terminal leads gets pinched, and the molten cream solder 4 is pushed out and comes into contact with the adjacent terminal lead 6 or land 3, causing a short circuit. It has become an obstacle.

[Problems to be Solved by the Invention] The present invention has been made in view of the problems of the conventional technology described above, and provides a solder joint that can eliminate short circuits caused by leakage of cream solder between adjacent conductor pattern surfaces 3. The purpose is to provide a method.

[Means to solve the problem]

In order to achieve the above object, in the present invention, the land 3 is divided into a plurality of sections, and a margin portion in which cream solder is not printed is formed in a part of the division, and the area of the cream solder printing surface 3a is equal to the area of the margin section. The amount of cream solder was changed depending on the ratio and the solder joints were made.

[Effect]

According to the above configuration, a part of the land 3 is divided to form a margin 5 of the cream solder 4 on the joint surface of the terminal lead, the cream solder 4 is divided into a plurality of surfaces and printed, and by reflow soldering, The cream solder 4 is evenly distributed on the bonding surface between the land 3 and the terminal lead including the margin 5, thereby preventing leakage of the cream solder 4 and preventing short circuits between adjacent terminal leads 6 or lands 3. can.

〔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 printed wiring lines vi and 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 joint surfaces of the open terminal leads and 6 are flush with each other.

A plurality of lands 3 are formed on the printed wiring board 2 in accordance with the bonding surfaces of the plurality of terminal leads 6, and at the same time guide marks or guide bin holes (not shown) are formed for positioning the printing mask 7 of the cream solder 4. ) are installed.

The printing mask 7 has a plurality of partitioned openings 8 formed in alignment with the bonding surface of the terminal wire 6 and the printed wiring Fi.
The opening 8 is aligned on the conductor pattern surface 3 using guide marks or guide bins.

From above the printing mask 7, the cream solder 4 is printed with a squeegee through a plurality of divided openings 8 onto the land 3 in a state divided by the cream solder printing surface 3a and the margin part 5.

The viscosity of the cream solder 4 depends on the room temperature at the time of use, and sagging or sagging occurs during printing. Therefore, the cream solder 4 should be printed in a temperature-controlled room and thoroughly stirred.

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

2, 3 and 4 are a partial plan view (a) and a partial side sectional view (b) showing details of the invention.

As shown in FIG. 2(a), a solder resist 9 is printed on the outer periphery of the lands 3 except for the solder joints and between the lands 3.

FIG. 2 shows a state in which the printing mask 7 of the cream solder 4 is positioned in accordance with the guide marks on the printed wiring board 2, and the two openings 8 formed in the printing mask 7.
A gap of 8 is formed.

FIG. 3 shows a state in which cream solder 4 is printed on land 3 using printing mask 7, and a margin 5 is formed in the center of cream solder printing surface 3a.

FIG. 4 shows a state in which the terminal leads 6 are soldered together, and the cream solder 4 melts and flows due to surface tension, filling the margin 5 and uniformly joining the terminal leads 6 and the lands 3.

By changing the ratio of the area of the cream solder printed surface 3a of the land 3 to the area of the margin part 5, the cream solder 4
By changing the amount of reflow soldering, it is possible to select an appropriate amount of ream solder 4 and printing conditions so that cream solder 4 does not leak toward adjacent terminal leads 6 or conductor pattern surfaces 3.

Although FIG. 2 shows an example in which the margin 5 is provided in the center, by providing a plurality of margins and forming the cream solder printed surface 3a on both sides or one side, the cream solder 4 can be averaged. The cream solder 4 flows out by reflow soldering, fills the margin 5, and uniformly joins the terminal lead 6 and the land 3.

〔Effect of the invention〕

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

Furthermore, when mounting electronic components, by using the exposed margin 5 of the cream solder 4 as a guide to correct the misalignment between the land 3 and the terminal lead 6, the positioning can be easily performed either manually or automatically. .

[Brief explanation of the drawing]

Figure 1 is a partially omitted perspective view illustrating the mounting of a flat package type electronic component on a printed wiring board. Figure 2 is a partially omitted partially sectional view and plan view showing the printing mask aligned with the land. Figure 3 is a partially omitted partial sectional view and plan view of the printed state of cream solder, and Fig. 4 is a partially omitted partial sectional view and plan view of the solder bonded state.
5 and 6 are partial plan views showing the conventional example and A
-A sectional view. In the figure, 1 is an electronic component, 2 is a printed wiring board, 3 is a land, 4 is cream solder, 5 is a margin, 6 is a terminal lead,
7 is a printing mask, 8 is an opening, and 9 is a solder resist. Patent applicant: Fujitsu General Ltd. Figures 5 and 6

Claims (2)

[Claims] (1) 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 led out from the main body of an electronic component, and the solder is bonded by reflow soldering, the above-mentioned Divide the land into multiple sections, form a margin where cream solder is not printed in a part of the section, and solder and join by changing the amount of cream solder depending on the ratio of the area of the cream solder printed surface to the area of the margin. A method of soldering and joining electronic components. (2) Claim (1) characterized in that cream solder printed surfaces are formed opposite both sides of the margin, and the margin is formed such that the cream solder penetrates into the margin by reflow soldering. Method of soldering the electronic components described.