JPH0837366A - Soldering method for board on which electronic parts are to be mounted and solder bonder - Google Patents

Abstract

PURPOSE:To uniformly bring molten solder into contact with the entire bottom face of a board on which electronic parts are mounted and avoid bringing due to growth of solder oxides. CONSTITUTION:A board (of 0.15-0.3mm thickness) 1 on which electronic parts are to be mounted has leads 13 laid over throug-holes 12. The back face of the board 1 at the through-hole side (opposite face to the lead-laid face) is contacted with a molten solder H enough to fill the through-holes therewith. A solder bonder has a solder processor 2 having a nozzle opening 21 and back- and-side face shield plate 22 the height difference L between which is 4-5mm. The board 1 is moved in a fixed direction so as to bring the back face 1B of the board 1 on the through-hole side into contact with the molten solder H overflowing from the processor 2 whereby the solder H is charged in the through-holes 12, without overflowing the molten solder on the front face 1A of the board 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder joining method for an electronic component mounting board and a solder joining apparatus for an electronic component mounting board. More specifically, the present invention uniformly applies molten solder to the entire back surface of the electronic component mounting board. The present invention relates to a solder joining method for an electronic component mounting substrate which can be brought into contact with each other and in which a bridge due to a solder oxide is not generated, and a solder joining apparatus for performing this process.

[0002]

2. Description of the Related Art As a conventional solder joining method for electronic component mounting boards, projecting pins of electronic components are exposed at a height of about 10 to 13 mm from the back surface of the electronic component mounting board. Therefore, as shown in FIG. 6, in order to immerse the back surface of the electronic component mounting substrate in the jet molten solder, the electronic component mounting substrate is lowered, immersed, and then further raised. As another conventional solder joining method, as shown in FIG. 3, there is provided an apparatus including a solder processing portion including a nozzle opening portion and a back surface / side surface side shielding plate in a box housing a circulating molten solder. The method used is known. In this device, since the protruding pins of the electronic component are exposed by about 10 mm on the rear surface of the electronic component mounting substrate to be processed, the height difference (L) between the nozzle opening and the rear surface / side surface side shielding plate (L) About 10 to 12 mm is required.
This is because if the height is not secured, the protruding pin and the nozzle will come into contact with each other.

[0003]

However, in the former joining method, the electronic component mounting substrate is not transported in a fixed direction, and the transportation system is complicated, which is not preferable for continuous processing. In the latter joining method, the height L from the nozzle openings of the back and side shields is about 10 mm.
Since it is high as described above, in order to overflow the solder, it is necessary to increase the rotation speed of the driving propeller and increase the ejection force. Therefore, the jet level becomes wavy and unstable, and there is a portion where the molten solder does not come into contact with the electronic component mounting substrate. Further, when the thickness of the electronic component mounting substrate is large, if the substrate is deeply dipped in a solder bath, it is possible to reduce non-wetting even if the jet molten solder is wavy, When it is thin, especially when it is 0.2 to 0.8 mm thick which is often used nowadays, when it is attempted to deeply immerse the electronic component mounting board in the solder bath, the solder is also applied to the upper surface side of the electronic component mounting board. It overflows and the surface side gets wet. Therefore, it cannot be deeply dipped in the solder bath, and the non-wetting is a serious problem. Further, increasing the ejection force causes the solder oxide to be agitated and circulated, so this solder oxide is usually present on the surface portion, but this reaches the inside or the lower side of the molten solder, and this further It will rise to the surface of the jet melted solder.
Therefore, there is also a problem that solder oxide adheres between the wirings of the electronic component mounting board, which causes a bridge.

The present invention is intended to solve the above-mentioned problems, and allows molten solder to be uniformly contacted with the entire back surface of an electronic component mounting substrate, thereby eliminating the occurrence of bridges due to solder oxide. It is an object of the present invention to provide a solder joining method for a board and a solder joining apparatus for performing this process.

[0005]

According to a first aspect of the present invention, there is provided a solder joining method for an electronic component mounting substrate, wherein a through hole side rear surface of the electronic component mounting substrate (lead arrangement) A surface opposite to the side surface is brought into contact with molten solder to fill the molten solder into the through hole and to electrically connect the through hole and the lead to an electronic component mounting substrate. In the solder joining method, the electronic component mounting board is mounted on the molten solder overflowing from the solder processing section of a solder joining apparatus including a solder processing section in which a height difference between a nozzle opening and a back surface / side surface side shielding plate is 8 mm or less. The electronic component mounting substrate is conveyed in a certain direction so that the back surface of the through hole side is brought into contact, the molten solder is filled in the through hole, and the electronic component is mounted. Characterized in that the surface side of the use substrate not to flood the molten solder.

According to another aspect of the present invention, there is provided a solder joining device for a substrate for mounting electronic parts, wherein a box body for containing molten solder and a height difference between a nozzle opening portion and a back surface / side surface side shielding plate disposed in the box body. Is 8 mm or less, a heating means for melting the solder, the molten solder is circulated and is pushed up from below the solder processing part to the nozzle opening.
A stirring means for jetting the molten solder pushed up from the nozzle opening.

The electronic component mounting substrate used in the present invention is an electronic component mounting substrate having leads (usually adhered and fixed to the surface of the base material by an adhesive) arranged on the through holes. By contacting the through hole side back surface (the surface opposite to the side surface on which the lead is arranged) with molten solder, the through hole is filled with solder and the through hole and the lead are soldered together. It is a board for mounting electronic components that is bonded. In such an electronic component mounting board, there is no protruding pin or protruding portion of the lead on the back surface side (for example, the flat lead 13 shown in FIG. 5), so when the molten solder is filled in the through hole, The height difference (L) between the nozzle opening and the back / side shields can be reduced. If this is 8 mm, soldering can be sufficiently performed.

In the above invention, when the height difference L between the nozzle opening and the back / side shields exceeds 8 mm, it is necessary to increase the rotational speed of the driving propeller and increase the ejection force. The jet level undulates and becomes unstable, resulting in non-wetting. In addition, the solder oxide is carried up to the surface of the jet melted solder, and solder oxide adheres between the wiring of the electronic component mounting board. Resulting in. Further, if this is 8 mm or less, when using an electronic component mounting board provided with electronic component foot pins (shown in FIG. 3), the pins and the nozzle openings are in contact with each other, which is not preferable. As can be seen from this, setting the thickness to 8 mm or less is significant also in relation to the type of electronic component mounting board to be used.

In the above invention, the height difference L is set to 0.2.
It can be ~ 5 mm. In this case, the problems of non-wetting and the adhesion of solder oxide are more unlikely to occur, and even if the size is reduced, there is little concern about contact between the back surface of the substrate and the nozzle opening. That is, in the conventional electronic component mounting board having the pin, the pin and the nozzle are surely brought into contact with each other.

[0010]

The present invention will be described below in detail with reference to examples. (1) Solder joining device As shown in FIG. 4, the present device is a box body (150φ to 450φmm × 200φmm × 800φ) that stores molten solder H.
mm) 3, the solder processing section 2 and the preliminary solder processing section 4 arranged in the box 3, the heating means 6 for melting the molten solder H, and the stirring means 5a, 5b for circulating the molten solder H.
Consists of The solder processing section 2 is composed of a nozzle opening 21 and a back surface / side surface side shielding plate 22, and a height difference L between them is 4 to 6 mm. Since the nozzle opening 21 is low, the jet melted solder overflows to the left (front) from the nozzle opening 21 side. The preliminary solder processing section 4 is an apparatus section for removing gas generated on the back surface of the conveyed electronic component mounting substrate, and the jet melted solder overflows to both the left and right (front and back).

The heating means 6 is an electric heater and is arranged in a large number on the inner peripheral side of the box body 3. The stirring means 5
Reference numerals a and 5b denote vane-shaped drive propellers that generate an upward flow by stirring. This is driven by a motor (not shown), and by this stirring, the molten solder H located below the solder processing section 2 is pushed up to the nozzle opening 21, and as a result overflows from the nozzle opening 21 and the molten solder H circulates. It will be. The two stirring means 5a and 5b are provided between the outer frame of the box body 3 and the solder processing section 3 and the preliminary solder processing section 4, as shown in FIG.
As shown in FIG. The solder composition used was tin 90% by weight: lead 10% by weight, but tin x% by weight: lead (100-x)% by weight may be used.

(2) Solder joining method First, an electronic component mounting substrate 1 as shown in FIG. 5 is prepared. The base material 11 of the electronic component mounting substrate 1 is made of glass cloth and bismaleimide / triazine resin, and its size is 25.0 mm × 25.0 mm × 0.15 to 0.80.
(Thickness) mm (particularly 0.15 to 0.3 mm).
Instead of glass cloth / bismaleimide / triazine resin, a material composed of glass cloth / epoxy resin or heat resistant resin such as polyimide may be used. A predetermined conductor circuit (made of copper foil) is formed on the surface of the electronic component mounting substrate 1. The conductor circuit is formed by usual etching, and the surface thereof is coated with a plating layer of gold / nickel or the like. An electronic component mounting portion (not shown) for mounting an electronic component (semiconductor chip or the like) is provided at the center of the electronic component mounting substrate 1, and a plurality of 0.3 mmφ penetrating the electronic component mounting substrate 1 ( 304) through holes 12 are provided. On the inner wall of the through hole 12, a through hole conductive layer 16 is formed by performing copper plating, then nickel plating and gold plating.

The plurality of leads 13 are supported by a lead frame (not shown), and the inner lead portions of the leads 13 are made of epoxy adhesive (thickness;
It is adhered and fixed to the front surface side of the base material 11 by about 10 to 80 μm, especially about 55 to 65 μm) 14. At this time, the lead 13 is arranged above the through hole 12.

This solder joining method is as follows, as shown in FIGS. 1 and 2. The treatment conditions are that the flux used is rosin-based (water-soluble), the immersion time is 2 to 15 seconds, and the solder temperature is 220 to 280 ° C. First, the electronic component mounting board 1 is transported in a fixed direction according to the transport line shown in FIG. 2, and at this time, the electronic component mounting substrate 1 comes into contact with the solder jetted from the preliminary solder processing section 4, and then the solder processing is performed. The back surface 1B of the electronic component mounting substrate 1 conveyed onto the portion 2 is further brought into contact with the solder jetted from the solder processing portion 2.

In the solder processing section 2, the height difference (L) between the nozzle opening 21 and the back surface / side surface side shielding plate 22 is 4 to 5 mm. Then, in order to secure the height of 4 to 5 mm, the stirring propeller is driven and stirred to push up the molten solder H and circulate it. The driving conditions of the stirring propeller in this case are as follows. Jet motor; 0.2K
W, frequency; 60 Hz.

Under this condition, the surface of the molten solder on the nozzle opening was not visually or substantially wavy, and a stable jet level was obtained. Also,
Under these conditions, when only the surface of the electronic component mounting substrate 1 was brought into contact with the molten solder H and the molten solder H was filled in the through holes 12, the unwetted through holes were not visually observed, and The through holes of No. 3 became wet, so that all the through holes were reliably filled with the molten solder, and the through holes 12 and the leads 13 were joined by the solder.

Further, under these conditions, since the solder oxide is lighter than the molten solder, it remains floating on the surface of the molten solder, and this is not stirred and circulated. It was not confirmed that the solder oxide floated. Therefore, the problem that solder oxide adheres between the wirings of the electronic component mounting board does not occur.

As described above, since the height difference L is reduced to 4 to 5 mm, the rotational speed of the driving propeller can be reduced, the solder can be overflowed even when the discharge force is small, and the pin on the back surface of the through hole side. Alternatively, since there is no protruding portion of the lead, even if this height difference L is made small, the soldering process can be performed reliably without contact with the nozzle opening, and the process can be performed in a very balanced manner. In particular, the thickness of the electronic component mounting board used was as thin as 0.15 to 0.3 mm, but since only the back surface of this board was contacted, or about 0.1 mm was immersed. Since the treatment was performed, the molten solder did not overflow onto the surface. In addition, the transfer direction of the electronic component mounting board is slightly upward (angle: 0 to 8).
Therefore, the overflow of the molten solder to the surface hardly occurs.

On the other hand, when the solder processing part having the height difference L of 10 mm is used and the molten solder H is jetted from the nozzle opening 21 of the solder processing part 2 under the stirring drive condition shown below, the nozzle It was visually confirmed that the surface of the molten solder on the opening was wavy. It was also confirmed that the solder oxide was lifted up to the jet melted solder and the oxide was circulated. Jet motor: 0.2 kW, frequency: 45 Hz.

(3) Manufacture of electronic component mounting apparatus Further, after soldering the through holes and the leads as described above, an electronic component mounting apparatus was manufactured as follows.
That is, the electronic component is arranged in the electronic component mounting portion at the center of the electronic component mounting substrate, and the electronic component and the conductor circuit on the surface of the electronic component mounting substrate are wire-bonded or the like,
It is electrically connected. A heat sink is arranged below the electronic component, if necessary. Next, this is placed in a predetermined cavity of a mold, and a sealing resin (epoxy resin, trade name;
"MP-7100", manufactured by Nitto Denko Corporation, is injected to seal the electronic parts and the like with resin.

The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application. That is,
The height difference L is not limited to that in the above embodiment, and can be made smaller than this, for example. It is also possible to set it to zero (0) mm. In the case of zero, the jet will flow in both left and right directions. As the height difference becomes smaller, the solder can be jetted with a smaller discharge force, so that the surface of the jet-melted solder becomes smoother and moreover, the solder oxide is not mixed into the jet-melted solder. The risk is also reduced. If this height difference L becomes too small,
The risk of contact between the back surface of the electronic component mounting board and the nozzle increases. Also, as the electronic component mounting board used,
One that has multiple board units and is elongated as a whole,
Further, this may be a long one having two or more units in the direction perpendicular to the carrying direction (that is, a multi-unit in the lateral direction). In these cases, soldering can be done continuously,
It is very useful.

[0022]

According to the method and apparatus of the present invention, since the height difference L is made as small as 8 mm or less, the rotational speed of the driving propeller can be lowered and the solder can be overflowed even when the ejection force is small. The jet melted solder on the nozzle opening can obtain a stable jet level. Therefore, the entire back surface of the electronic component mounting substrate can be uniformly wetted, and all the through holes can be reliably filled with solder. In addition, since the solder oxide is not circulated, the solder oxide does not float in the molten solder on the nozzle opening, and therefore the problem of bridging does not occur.

[Brief description of drawings]

FIG. 1 is an enlarged explanatory view of a solder processing unit used in this embodiment.

FIG. 2 shows a state in which an electronic component mounting board having through holes to be filled with molten solder is brought into contact with the molten solder jetted from the solder processing unit and the preliminary solder processing unit used in this embodiment for soldering. FIG.

FIG. 3 is an explanatory diagram showing a state in which a molten solder jetted from the solder processing unit and the preliminary solder processing unit shown in FIG.

FIG. 4 is an explanatory cross-sectional view of a solder processing apparatus for an electronic component mounting board according to the present embodiment.

FIG. 5 is a partial explanatory view of an electronic component mounting board having through holes to be filled with molten solder used in this embodiment.

FIG. 6 is an explanatory diagram showing a state in which an electronic component mounting substrate having protruding pins on the back surface is brought into contact with the molten solder in the solder dipping device to perform soldering processing.

[Explanation of symbols]

1; electronic component mounting substrate; 12; through hole; 16;
Through-hole conductive layer, 14; Adhesive layer, 13; Lead, 1
1; base material, 1A; front surface, 1B; back surface, 2; solder processing part,
21; Nozzle opening, 22; Back / side shield plate, 3; Box, 4; Pre-soldering parts, 5a, 5b; Stirring propeller, 6;
Heater, H: molten solder, L: height difference between nozzle opening and back / side shield plate.

Claims (4)

[Claims] 1. An inside of the through hole by contacting a through hole side rear surface (a surface opposite to the side surface on which the lead is arranged) of a substrate for mounting an electronic component equipped with a lead arranged on the through hole with a molten solder. In the solder joining method of the electronic component mounting substrate for electrically connecting the through hole and the lead while filling the molten solder into the solder, the height difference between the nozzle opening and the back surface / side surface side shielding plate Is 8 mm
The electronic component mounting board is transported in a certain direction so that the molten solder overflowing from the solder processing section including the solder processing section is brought into contact with the through hole side back surface of the electronic component mounting board. A method of solder joining an electronic component mounting substrate, characterized in that the molten solder is filled in the through hole and the molten solder does not overflow onto the surface side of the electronic component mounting substrate. 2. The thickness of the electronic component mounting substrate is 0.2.
2. The method for manufacturing an electronic component mounting substrate according to claim 1, wherein the height difference between the nozzle opening and the back surface / side surface side shielding plate is 0.2 to 5 mm. 3. A box for accommodating the molten solder, a solder processing section which is arranged in the box and has a height difference between the nozzle opening and the back / side shields of 8 mm or less, and melts the solder. Heating means and a stirring means for circulating the molten solder and pushing up the molten solder from below the solder processing portion to the nozzle opening and jetting the pushed up molten solder from the nozzle opening. A solder joining device for electronic component mounting boards, characterized in that 4. The solder joining device for an electronic component mounting board according to claim 3, wherein a height difference between the nozzle opening and the back surface / side surface side shielding plate is 0.2 to 5 mm.