JP2000165029A - Method of mounting electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mixedly mount insert mount components and surface mount components on a board at a high reliability by mounting lead insert type electronic components subjected to a solder bond pre-treatment step and reflowing solder to solder them to the board. SOLUTION: Surface mount component solder lands are printed with solder paste on a surface B 22 of a board 18, the board 18 is reversed, a thermosetting adhesive is coated near openings of through-holes 44 for inserting straight insert components on a surface A 20, thereby forming an adhesive layer, straight insert components 28 and other insert components than the components 28 are inserted in the through-holes 44 of the board 18 from the surface 20, the tips are clinched, the board 18 is reversed with the surface B 22 up, surface mount components, i.e., chip components and package components are mounted, the board 18 is sent to a reflow apparatus with the surface B 22 up, and solder is molten and cooled to form solder zones, thus securing all the components to the board 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting an electronic component, and more particularly, to a method for mounting an electronic component for forming a highly reliable solder joint.

[0002]

2. Description of the Related Art In the field of mounting electronic components such as IC packages and connectors as well as the miniaturization of electronic / electric devices, methods for reducing the size of mounting boards and mounting electronic components at high density have been actively studied and developed. ing. An electronic component to be mounted (hereinafter, referred to as a mounting component) is an insertion type mounting component (hereinafter, referred to as an insertion mounting component) in which a lead or a pin of the mounting component is inserted into a through hole provided in a mounting board and soldered.
And a surface-mounted electronic component (hereinafter, referred to as a surface-mounted component) that joins a solder land provided on the surface of a mounting board to an electrode or a lead of the electronic component.

[0003] The insertion mounting component includes a straight insertion type insertion mounting component (hereinafter simply referred to as a straight insertion component).
And a lead clinch type insertion part (hereinafter simply referred to as a clinch insertion part). As shown in FIG. 4, the straight insertion component 26 inserts a lead (or pin) 42 into a through hole 44 of the
This is a method of forming and joining the solder joint 30 between the tip of the lead and the copper land 52, and is a method of inserting the lead (or pin) 42 without clinching. On the other hand, as shown in FIG. 5, the clinch insertion parts 24 and 25 insert the leads (or pins) 54 into the through holes 44 of the substrate 18 and then clinch the tips of the leads (or pins) 54,
This is an insertion component of a method of forming and joining the solder joint 30 between the tip of the lead 54 and the copper land 52.

Conventionally, when mounting components are mounted on a board by soldering, a flow soldering method or a solder jet method has been adopted as a solder film forming method. The flow soldering method or the solder jet method is a method in which a solder jet is made to collide with a solder jet at a portion to be soldered to apply solder, thereby forming a solder film. Here, referring to FIGS. 6 and 7,
A conventional method of mounting and mounting an insertion mounting component and a surface mounting component on a substrate will be described below. 6 (a) and (b) and FIG.
(C) to (e) are cross-sectional views of a substrate explaining steps of a conventional mounting method of a mounted component. As shown in FIG. 6 (a), the clinch insertion parts 12, 14, 16 except for the straight insertion parts are connected to one surface of the substrate 18, the A surface 20.
And the lead 19 is clinched and fixed. Then
As shown in FIG. 6B, the other surface of the substrate 18, B
A thermosetting adhesive is applied to a predetermined area of the surface 22 to form an adhesive layer 24.

Subsequently, as shown in FIG.
A surface mount component such as a chip component 25 such as a capacitor or a package component 26 such as a QFP or SOP is disposed on the adhesive layer 24, and the substrate 1 is cured by a thermosetting adhesive of the adhesive layer 24.
Temporarily fix to 8. Next, as shown in FIG.
As shown in FIG. 7 (e), a straight insertion part 28 is inserted from the surface 20, and then the B side 22 is collectively soldered by flow soldering using a flow soldering device to form a solder joint 30. Are formed and joined.

[0006]

In this conventional method,
There were the following problems of poor solder joints. That is,
Since the formation of the solder film is performed by the flow soldering method, soldering defects such as bridges, icicles, and unsoldered are likely to occur at the solder joints. In addition, in order to perform highly reliable soldering, it is necessary to set the shape of the solder jet in the flow solder bath and the jet speed of the solder jet to be optimal for solder joining. There is also a problem that it is difficult to optimally set the shape of the solder jet and the jet speed. On the other hand, in stationary AV equipment and the like, an insertion mounting component and a surface mounting component are often mixedly mounted on a board, and it is desired to develop a mounting method with high reliability.

Therefore, an object of the present invention is to provide a highly reliable
Mixed mounting of insert mounting components and surface mounting components on a board,
It is to provide a mounting method of a mounted component.

[0008]

In order to achieve the above object, a method of mounting an electronic component according to the present invention is directed to a method for mounting a lead-insertable electronic component in a liquid flux for terminal processing housed in a first flux tank. Immersing the lead with the liquid flux for terminal treatment, and immersing the lead coated with the liquid flux for terminal treatment in the solder contained in the stationary solder bath, and coating the lead with solder,
Immersing the lead coated with the solder in the low-residual liquid flux contained in the second flux tank, and coating the lead with the low-residual liquid flux; It is characterized in that a lead insertion type electronic component that has undergone a solder joint pre-processing step is mounted on a substrate and soldered to the substrate by reflow processing.

[0009] In the solder coating step, the amount of solder to be coated is such that a good solder joint can be formed. In the present invention, the low-residual liquid flux coated on the leads improves the solder wettability of the solder lands on the substrate. Preferably, following the step of coating the low residue liquid flux,
And a heating step for volatilizing the solvent component of the low-residue liquid flux. Further, after the step of coating the lead with the solder, the method further includes a step of drawing the lead through a hole such as a die. This facilitates lead insertion into the through hole of the substrate.

When a lead insertion type electronic component is mounted on a board and soldered to the board by reflow processing,
For straight lead type lead insertion type electronic parts, insert the lead into the through hole of the board, and for clinch lead type lead insertion type electronic parts, insert the lead into the through hole of the board, clinch the tip of the lead, and then Then, the substrate and the electronic component are sent together into a reflow furnace.

Also, the method of the present invention can be applied to a surface mount type electronic component having leads. That is, in the method for mounting an electronic component according to the present invention, the lead of the surface-mounted electronic component is immersed in the liquid flux for terminal treatment accommodated in the first flux tank, and the lead is coated with the liquid flux for terminal treatment. And dipping the lead coated with the liquid flux for terminal treatment in the solder contained in the stationary solder bath, and coating the lead with the solder. In the low residue liquid flux contained in the second flux bath, Immersing a lead coated with solder into a lead, and coating the lead with a low-residual liquid flux. It is characterized in that it is mounted on a substrate and soldered to the substrate by reflow processing.

When mounting a surface mount type electronic component on a board and soldering the board to the board by reflow processing,
The surface-mounted electronic component is arranged and temporarily fixed on an adhesive layer formed on the substrate, and then the substrate and the electronic component are sent together to a reflow furnace and soldered to the substrate by reflow processing.

When a surface-mounted electronic component and a lead insertion type electronic component are mixedly mounted on a substrate, the lead insertion type mounting component and the surface mounting type electronic component are mounted by the above-described electronic component mounting method.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of an embodiment in which a mounting component mounting method according to the present invention is applied to mounting of an insertion mounting component.
FIG. 1 is a cross-sectional view of a substrate for explaining pre-processing of leads of a mounted component, and FIGS. 2 (a) to 2 (c), 3 (d) and 3 (e).
FIGS. 4A and 4B are cross-sectional views of a substrate for describing steps of a method of mounting an electronic component according to the embodiment. The method for mounting an electronic component according to the present embodiment includes a pre-processing step for a lead of an inserted mounting component and a board mounting step.

Pretreatment step (1) A first flux tank (not shown) filled with a liquid flux for terminal treatment, for example, a liquid flux of trade name T-1 manufactured by Senju Metal Industry Co., Ltd. A second flux tank (not shown) filled with a colorless and transparent liquid flux, for example, a liquid flux of trade name ZR-91 manufactured by Senju Metal Industry Co., Ltd .; and a stationary solder tank filled with molten solder (not shown). Zu) are prepared. (2) In order to ensure the solder wettability of the lead portion of the insertion mounting component, the lead portion of the insertion mounting component is immersed in the first flux bath to coat the lead with the flux. At this time, after the lead is inserted into the through hole of the board, the lead is inserted into the through hole of the board up to, for example, about 8 mm above the tip of the lead, and then the lead is cut. For the mounted component, the lead is coated with the flux by immersing it in the flux up to about 8 mm above the cutting position.

(3) Next, the lead portion coated with the T-1 flux is immersed in a stationary solder bath, and the lead is coated with solder. At this time, after the lead is inserted into the substrate, about 20 mg of the inserted mounting component that does not cut the lead is attached to the lead portion, for example, about 8 mm above the tip of the lead.
Coat the solder. After the lead is inserted into the board, for an insertion-mounted component that cuts the lead, about 20 mg of solder is coated on the lead portion about 8 mm above the cutting position. (4) Next, the lead portion coated with the solder is formed with a jig such as a die, and the unevenness on the surface is removed so that the lead can be easily inserted into the through hole of the substrate. (5) The solder-coated portion of the lead of the insertion mounting component is immersed again in the second flux bath, and coated with a low residue flux of ZR-91. The flux applied here is for the purpose of improving the solder wettability of the substrate land by the lead coming into contact with the substrate land during mounting. (6) The entire insertion mounted component is heated to a temperature of about 70 to 80 ° C. to evaporate the solvent component of the low-residue flux. As a result, the lead surface is not sticky, handling is extremely simple and easy, and the colorless and transparent flux improves the appearance of the lead.

The leads of the inserted mounting components inserted into the through holes of the board by the above pretreatment are as shown in FIG. In FIG. 1, the lead 42 of the straight insertion component 26 is inserted into a through hole 44 of the substrate 18, and a solder layer 48 and a flux layer 50 outside the solder layer 48 are formed at the tip 46 of the lead 42. B of substrate 18
The copper land 5 is provided at the opening edge of the through hole 44 on the surface 22 side.
2 are provided.

Substrate Mounting Step The diameter of the through hole for inserting the lead of the substrate 18 used in the present embodiment is determined by the lead 42 of the pre-processed inserted mounting component.
, For example, about 2.
A through hole having a diameter slightly larger than the diameter of a through hole of a normal substrate is provided. (7) First, as shown in FIG. 2A, the solder paste 54 is printed on the solder lands for surface mounting components on the B surface 22 of the substrate 18 by a screen printer (not shown). In the present embodiment, the solder paste of the surface mount component must be printed because the pretreatment of the method of the present invention is not performed on the lead of the surface mount component when soldering the surface mount component. (8) Next, as shown in FIG. 2B, the substrate 18 is turned over, and a through hole (not shown) for inserting a straight insertion part is heated by a dispenser (not shown) in the vicinity of the opening on the A surface 20 side. An adhesive layer 24 is formed by applying a curable adhesive. (9) Subsequently, as shown in FIG. 2C, from the side of the A side 20, a straight insertion part 2 such as a DIP, a transistor, etc.
8, and clinch insertion parts other than straight insertion parts,
For example, leads such as the resistor 12, the capacitor 14, and the diode 16 are inserted into through holes (not shown) of the substrate 18, and the tips are clinched. In addition, straight insertion part 2
8 is sent to the reflow device as it is on the substrate 18, so that it is not necessary to temporarily fix it.

(10) Next, the substrate 18 is turned over and the
2 upward, and using a mounter (not shown), chip components 25 and Q such as surface mount components QFP, SOP, etc.
The package components 26 such as FP and SOP are mounted. (11) Subsequently, with the B-side 22 facing upward, the substrate 18
Is fed into a reflow device (not shown), the solder is melted, and then cooled and solidified to form a solder joint 30 as shown in FIG. I do.

By the mounting process described above, in the straight insertion part 26, as shown in FIG. 4, the solder joint 30 is formed between the lead 42 and the copper land 52, and is electrically and mechanically strongly connected to each other. Connecting. As a result, the straight insertion component 60 is mechanically firmly mounted on the board 18. FIG. 4 is a cross-sectional view of a board explaining a solder joint of a straight insertion component. Further, in the clinch insertion parts 25 and 26, as shown in FIG.
Are formed between the clinched leads 54 and the copper lands 52, and are firmly electrically and mechanically interconnected. Thereby, the clinch insertion parts 25 and 26 are mechanically and firmly mounted on the board 18. FIG. 5 is a cross-sectional view of a board explaining a solder joint of the clinch insertion component.
In addition, as described in the second embodiment, the surface mount component
By applying the method of the present invention, a good solder joint is formed.

Second Embodiment Also, by performing the pre-processing performed in the first embodiment on the leads of the surface mount components such as QFP and SOP, the solder paste is not printed as in the first embodiment. Solder joining can be performed using a reflow device.
Heretofore, surface mount components such as QFPs and SOPs have only been subjected to solder coating, but flux printing is required. However, the method of the present invention has an effect that it is not necessary to apply a flux.

When the method for mounting an electronic component according to the present invention is applied to a surface mount component such as a QFP or an SOP, the surface mount type electronic component is contained in a liquid flux for terminal treatment accommodated in a first flux tank. The lead is immersed, and the lead is coated with a liquid flux for terminal treatment. Next, the lead coated with the liquid flux for terminal treatment is immersed in the solder contained in the stationary solder bath, and the lead is coated with the solder.
Subsequently, the lead coated with solder is immersed in the low-residual liquid flux accommodated in the second flux tank, the lead is coated with the low-residual liquid flux, and further heated to remove the solvent of the low-residual liquid flux. Evaporate the components. Less than,
A surface-mounted electronic component that has undergone a solder joint pre-processing step is mounted on a board, and solder-joined to the board by reflow processing. As described above, in the present embodiment, it is not necessary to print the solder paste on the substrate land.

[0023]

According to the method of the present invention, soldering can be performed by reflow processing by applying solder to the leads in the pretreatment step. This eliminates the occurrence of solder joint failures such as bridges, icicles, and solder unjoint, which have occurred in the conventional flow soldering process, and realizes highly reliable solder mounting of electronic components. In flow soldering, setting the shape of the solder jet and the speed of the solder jet was difficult and time-consuming work.However, in the method of the present invention, the lead was immersed in the solder in the stationary solder bath, so the It is not necessary to make complicated settings such as the shape of the
The workability of the soldering work is improved. Further, once the temperature profile in the reflow device is set by the reflow process using the reflow device, highly reliable soldering can be easily realized with high reproducibility.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a substrate for describing pre-processing of leads of a mounted component.

FIGS. 2A to 2C are cross-sectional views of a board explaining steps of a method of mounting a mounted component according to an embodiment of the present invention.

3 (d) and 3 (e) respectively show FIG. 2 (c)
3 is a cross-sectional view of a substrate for explaining steps of a mounting method of the mounted component according to the embodiment.

FIG. 4 is a cross-sectional view of a board explaining a solder joint of a straight insertion component.

FIG. 5 is a cross-sectional view of a board explaining a solder joint of a clinch insertion component.

FIGS. 6A and 6B are cross-sectional views of a board explaining steps of a conventional mounting method of a mounted component.

FIGS. 7 (c) to 7 (e) correspond to FIGS.
FIG. 4B is a cross-sectional view of the substrate, explaining a step of the conventional mounting method of the mounted component, following FIG.

[Explanation of symbols]

12, 14, 16 ... clinch insertion part, 18 ... board, 20 ... A side, 22 ... B side, 24 ... adhesive layer,
25 ... chip parts, 26 ... package parts, 28 ...
... Straight insertion part, 30 ... Solder joint, 42 ...
... Lead, 44 ... Through hole, 46 ... Lead tip, 48 ... Solder layer, 50 ... Flux layer, 52 ...
... copper land, 54 ... clinch lead.

Claims (7)

[Claims] A step of immersing a lead of the lead insertion type electronic component in a liquid flux for terminal treatment accommodated in a first flux tank and coating the lead with the liquid flux for terminal treatment; and accommodating the lead in a stationary solder tank. Dipping the lead coated with the liquid flux for terminal treatment into the solder that has been processed, and coating the lead with the solder; and dipping the lead coated with the solder into the low-residue liquid flux contained in the second flux tank. And a step of coating the lead with a low-residual liquid flux.The step of pre-solder-joining the lead comprises: mounting the lead-insertion-type electronic component that has undergone the solder-joining pre-processing step on a substrate; An electronic component mounting method characterized by soldering. 2. The method according to claim 1, further comprising, after the step of coating the lead with solder, a step of polishing and surface finishing the lead. 3. When the lead insertion type electronic component is mounted on a substrate and soldered to the substrate by a reflow process,
For straight lead type lead insertion type electronic parts, insert the lead into the through hole of the board, and for clinch lead type lead insertion type electronic parts, insert the lead into the through hole of the board and clinch the tip of the lead. 2. The method according to claim 1, wherein the substrate and the electronic component are sent together into a reflow furnace. 4. A step of immersing a lead of a surface-mounted electronic component in a liquid flux for terminal treatment accommodated in a first flux tank, and coating the lead with the liquid flux for terminal treatment, A step of immersing the lead coated with the liquid flux for terminal treatment in the contained solder, and coating the lead with the solder; and a step of immersing the lead coated with the solder in the low residue liquid flux contained in the second flux tank. And a step of coating the lead with a low-residual liquid flux. A method for mounting an electronic component, which is performed by soldering to a substrate. 5. When mounting a surface-mount type electronic component on a board and soldering the board to the board by reflow processing,
Place the surface-mounted electronic components on the adhesive layer formed on the board and temporarily fix them, then send the board and the electronic components together into a reflow furnace and solder them to the board by reflow processing The method for mounting an electronic component according to claim 4, wherein: 6. The method according to claim 1, further comprising a heating step of volatilizing a solvent component of the low-residual liquid flux after the step of coating the low-residual liquid flux.
The mounting method of the electronic component according to any one of the above. 7. The method according to claim 1, wherein when the electronic component of the surface mount type and the electronic component of the lead insertion type are mixedly mounted on the substrate.
A method for mounting a lead insertion type mounting component by the method for mounting an electronic component according to any one of the above, and mounting a surface mounting type electronic component by a method for mounting an electronic component according to claim 4 or 5. Characteristic electronic component mounting method.