JP2019140330A - Soldering method and mask for screen printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soldering method and a mask for screen printing which improve joining quality while suppressing a decrease in production efficiency and an increase in cost. SOLUTION: The soldering method is a first reflow in which a first reflow is performed after a first coating step of applying a solder paste to a land 13 on one surface S of a substrate 11 and a first coating step. A step, a second coating step of applying the solder paste 32 to the lands 14 and the through holes 12 on the other surface P of the substrate 11, and a mounting step of inserting the leads 33 into the through holes 12 after the second coating step. And a second reflow step of performing a second reflow after the mounting step. [Selection diagram] Fig. 2

Description

  The present invention relates to a soldering method and a mask for screen printing.

  There is a technique in which a solder paste is printed on a through hole of a circuit board, a lead of an electronic component is inserted into the through hole, and soldering is performed by reflow. When part of the solder paste falls from the circuit board by pushing out the solder paste in the through hole at the tip of the lead when the lead is inserted, the remaining amount of the solder paste is reduced, resulting in poor soldering. there is a possibility. Patent Document 1 proposes that the tip of the lead be tapered to suppress the extrusion of the solder paste.

JP 2017-41576 A

When all the leads of the electronic component are tapered, there is a possibility that the production efficiency is reduced and the cost is increased.
The subject of this invention is improving the quality of soldering, suppressing the fall of production efficiency and the increase in cost.

  A soldering method according to an aspect of the present invention is a soldering method for inserting and soldering electronic component leads into a through-hole of a board, and each of one side and the other side of the board is soldered. A land to be connected to the through hole is formed, and a first application process for applying solder paste to the land on one surface of the substrate, and a first reflow for performing the first reflow after the first application process After the step, the second coating step of applying solder paste so as to cover the land and the through hole formed on the other surface of the substrate, and after the second coating step, the lead of the electronic component is inserted into the through hole A mounting step and a second reflow step for performing a second reflow after the mounting step.

  A screen printing mask according to an aspect of the present invention is a screen printing mask used for inserting and soldering electronic component leads into a through hole of a substrate, and is used to expose the land. An opening formed larger than the outer diameter, and a shielding part without an opening, which is formed larger than the inner diameter of the through hole and disposed inside the opening, are provided to cover the through hole.

According to the present invention, when the first application step and the first reflow step are performed, the solder is welded to the land on one surface of the substrate. Then, when the second coating step and the mounting step are performed, the solder paste pushed out by the insertion of the lead comes into contact with the solder welded to the land. Then, when the second reflow process is performed, the solder paste is melted and the solder welded to the land is remelted so that they are integrated. Thus, by adding the solder that has been welded in the first reflow process, it is possible to prevent a situation in which the solder is reduced and soldering is poor, and the quality of soldering can be improved. In addition, a decrease in production efficiency and an increase in cost can be suppressed as compared with a case where all leads are tapered.
When performing the first coating step, the first screen printing mask is used. Since this screen printing mask includes an opening that exposes the land and a shield that covers the through hole, it is easy to apply the solder paste to the land on one surface.

It is sectional drawing which shows the soldering method (ad). It is sectional drawing which shows the soldering method (eh). It is a top view of the 1st mask for screen printing used at the 1st application process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, each drawing is schematic and these may differ from an actual thing. Further, the following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the configuration is not limited to the following. That is, the technical idea of the present invention can be variously modified within the technical scope described in the claims.

<Embodiment>
"Constitution"
1 and 2 are cross-sectional views showing a soldering method.
As shown in FIG. 1A, the substrate 11 is provided with a through hole 12. The land 13 is formed on one surface S of the substrate 11, the land 14 is formed on the other surface P of the substrate 11, and the through hole 12 is connected to the land 13 and the land 14. Here, the board | substrate 11 is arrange | positioned so that one surface S may become an upper side.
First, as shown in FIG. 1B, a first screen printing mask 21 (screen printing mask) is placed on one surface S of the substrate 11, and a solder paste 22 is applied to the lands 13. Since the mask 21 covers the through hole 12, the solder paste 22 is applied only to the land 13. This is the first coating step.

Next, as shown in FIG. 1C, the mask 21 is separated from the substrate 11.
Next, reflow is performed as shown in FIG. This is the first reflow process. As a result, the solder paste 22 is melted and then becomes the solder 23 welded to the land 13.
Next, as shown in FIG. 2 (e), the substrate 11 is arranged so that the other surface P faces upward.
Next, as shown in FIG. 2 (f), a second screen printing mask 31 (screen printing mask) is placed on the other surface P of the substrate 11, and solder paste 32 is placed on the lands 14 and the through holes 12. Apply. This is the second coating step.

Next, as shown in FIG. 2G, electronic component leads 33 are inserted into the through holes 12 from the other surface P of the substrate 11. This is the mounting process. At this time, the solder paste 32 on the through hole 12 is pushed into the through hole 12 by the lead 33, and then a part of the solder paste 32 in the through hole 12 is pushed onto one surface S of the substrate 11. The solder paste 34 protruding to the outside contacts the solder 23 welded to the land 13.
Next, reflow is performed as shown in FIG. As a result, the solder pastes 32 and 34 are melted, and the solder 23 welded to the lands 13 is remelted so that they are integrated. The solder 35 is welded to the land 14 on the other surface P of the substrate 11, and the solder 33 is welded to the land 13 on one surface S of the substrate 11, whereby the lead 33 is joined to the land 13. This is the second reflow process.
The above is the soldering method.

Next, the first screen printing mask 21 which is a screen printing mask will be described.
FIG. 3 is a plan view of a first mask for screen printing used in the first application step.
The first screen printing mask 21 includes an opening 41, a shielding part 42, and a connecting part 43.
The opening 41 is formed in a circular shape. The opening 41 is formed larger than the outer diameter r <b> 1 of the land 13 in order to expose the land 13. The size of the opening 41 is appropriately adjusted according to the required amount of solder.
The shielding part 42 is formed in a disk shape. The shielding part 42 is disposed inside the opening 41. The shielding part 42 is formed larger than the inner diameter r <b> 2 of the through hole 12 in order to cover the through hole 12.
The connecting portion 43 connects the inner peripheral side of the opening 41 and the outer peripheral side of the shielding portion 42 in order to support the shielding portion 42 provided inside the opening 41.

<Effect>
Next, the effect of embodiment is demonstrated.
When the lead 33 is inserted, if the solder paste in the through-hole is pushed out at the tip of the lead 33, the solder paste partially falls from the substrate, and the remaining amount of the solder paste may be reduced, resulting in poor soldering. There is sex. In order to suppress the extrusion of the solder paste, it is conceivable that the tip of the lead 33 is tapered. However, it is not practical to taper all the leads, resulting in a decrease in production efficiency and an increase in cost.
Therefore, first, the solder paste 22 is applied to the land 13 on the one surface S of the substrate 11 (first application step). Then, reflow is performed (first reflow process). Next, a solder paste 32 is applied so as to cover the lands 14 and the through holes 12 on the other surface P of the substrate 11 (second application step). Then, the lead 33 is inserted into the through hole 12 (mounting process). Then, reflow is performed (second reflow process).

  When the first application step and the first reflow step are performed, the solder 23 is welded to the land 13 on one surface S of the substrate 11. Then, when the second coating process and the mounting process are performed, the solder paste 34 pushed out by the insertion of the leads 33 comes into contact with the solder 23 welded to the lands 13. Then, when the second reflow process is performed, the solder paste 34 is melted and the solder 23 welded to the land 13 is remelted so that they are integrated. The solders 35 and 36 are formed with fillets that are wet and spread at the bottom. Thus, by adding the solder 23 that has been welded, it is possible to prevent a situation in which the solder is reduced and soldering is poor, and the quality of soldering can be improved. In addition, it is possible to suppress a decrease in production efficiency and an increase in cost compared to the case where all the leads 33 are tapered.

  When performing the first coating step, the first screen printing mask 21 is used. The first screen printing mask 21 includes an opening 41 that exposes the land 13 and a shielding part 42 that covers the through hole 12. The shielding part 42 is larger than the inner diameter r 2 of the through hole 12. Yes. As a result, the solder paste 22 can be applied only on the land 13, and the through hole 12 is not blocked by the solder 23 after the first reflow process. It is possible to avoid a problem in the process that the lead 33 cannot be inserted into the through hole 12 in the mounting process.

  Although the present invention has been described with reference to a limited number of embodiments, the scope of rights is not limited thereto, and modifications of the embodiments based on the above disclosure are obvious to those skilled in the art.

DESCRIPTION OF SYMBOLS 11 Board | substrate 12 Through-hole 13 Land 14 Land 21 Mask 22 Solder paste 23 Solder 31 Mask 32 Solder paste 33 Lead 34 Solder paste 35 Solder 36 Solder 41 Opening 42 Shielding part 43 Connecting part

Claims (3)

A soldering method for inserting and soldering electronic component leads into a through hole of a board,
Lands connected to the through holes are formed on each of the one surface and the other surface of the substrate,
A first application step of applying a solder paste to the land formed on one surface of the substrate;
A first reflow step for performing a first reflow after the first application step;
A second application step of applying a solder paste to the land and the through hole formed on the other surface of the substrate;
After the second coating step, a mounting step of inserting the lead of the electronic component into the through hole;
And a second reflow step for performing a second reflow after the mounting step. In the first application step,
The soldering method according to claim 1, wherein the through hole is covered with a first screen printing mask, and the solder paste is applied only to the land. A screen printing mask used for soldering by inserting the lead of an electronic component into a through hole of a board,
An opening formed larger than the outer diameter of the land to expose the land;
A screen printing mask, comprising: a shielding portion that is formed larger than an inner diameter of the through hole and disposed inside the opening to cover the through hole.

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