JPH01312802A - Solder-coating method for chip part - Google Patents

Abstract

PURPOSE:To enable solder coating to be made to an external electrode of chip parts uniformly and easily by allowing solder to be adhered to the external electrode of the chip parts and by heating solder adhered to the external electrode of the chip parts in floating status of the chip parts within air and liquid for fusing. CONSTITUTION:A solder 23 is adhered to external electrodes 2 and 3 of chip parts. Then, when the solder 23 adhered to the external electrodes 2 and 3 of the chip parts is heated in floating status of the chip parts and fuses, it coats the entire external electrodes 2 and 3 of the chip parts entirely by surface tension and pressure applied externally in liquid and the external surface is formed in a smooth shape and is corrected. Thus, solder film can be formed uniformly and easily on the surface of the external electrodes 2 and 3 of a chip capacitor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for solder coating chip components such as a chip resistor or a chip capacitor, in which external electrodes of the chip components are coated with a solder film.

[Prior Art] Generally, chip components such as chip resistors and chip capacitors are soldered directly to a pattern on a printed circuit board using an external electrode formed on a part of their outer surface.

For example, in a chip capacitor I having a shape as shown in FIG. 6, its external electrodes 2 and 3 usually protect it and facilitate soldering to a pattern on a printed circuit board (not shown). Therefore, it is coated with a solder film (not shown).

Conventionally, as a solder coating method for coating the external electrodes 2 and 3 of the chip capacitor I with a solder film, as shown in FIG. 7, for example, as shown in FIG. A well-known method is to hold the external electrodes 2 (and 3) by immersing them in molten solder 4 and pulling them up as shown by arrows AI, thereby adhering the solder to the external electrodes 2 and 3.

[Problems to be Solved by the Invention] By the way, in the above conventional solder coating method for chip components, when the dimensions of the chip capacitor l become smaller,
It is difficult to hold the chip capacitor l with a bottle set, etc., immerse the external electrodes 2 and 3 in the molten solder 4, pull it up, and apply solder coating to the external electrodes 2 and 3, and it is also difficult to automate the solder coating. It was also difficult to control the amount of solder attached to the external electrodes 2 and 3.

It is an object of the first and second inventions of the present application to provide a method for solder coating a chip component, which can uniformly and easily apply solder coating to the external electrodes of the chip component.

[Means for Solving the Problem] Therefore, the first invention of the present application is a solder coating method for a chip component, which coats the external electrode of the chip component with a solder film, the method comprising: attaching solder to the external electrode of the chip component. The method is characterized in that the solder adhered to the external electrodes of the chip component is heated and melted while the chip component is floating in a gas or liquid, and then the chip component is cooled.

Further, a second invention of the present application is a solder coating method for a chip component in which external electrodes of the chip component are coated with a solder film, in which a substrate to which molten solder is difficult to adhere is prepared, and the surface of the substrate is coated with the above-mentioned chip. Print solder paste corresponding to the external electrodes of the component, align the external electrodes of the chip component with the printed solder paste, place the chip component, and heat the board to melt the solder paste and solder the chip component. Solder is attached to the external electrode, and then the solder attached to the external electrode of the chip component is heated and melted while the chip component is floating in a gas or liquid, and then the chip component is cooled. It is characteristic.

[Function] In the first invention of the present application, when the solder attached to the external electrode of the chip component is heated and melted while the chip component is floating, the surface tension of the solder and the pressure applied from the outside in the liquid cause the solder to melt on the outside of the chip component. The shape is corrected by covering the entire electrode and molding the outer surface into a smooth shape.

In the second invention of the present application, when the board is placed in a reflow oven or the like and heated, the solder paste printed on the board melts and becomes molten solder. This molten solder does not adhere to the substrate, but completely adheres to the external electrodes of the chip component due to its wetting action. In this state, the shape of the solder attached to the external electrodes of the chip component becomes distorted on the surface of the substrate and at positions distant from the surface due to the weight of the chip component. This process heats the chip component in a floating state and remelts the solder attached to the surface of its external electrode, causing the solder to form a smooth shape on the external surface due to its surface tension and external pressure in the liquid. Shaped and modified.

[Effects of the Invention] According to the first invention of the present application, there is no need to hold the chip component with a jig during solder coating of the external electrode of the chip component. Solder coating can also be automated.

Further, according to the second invention of the present application, the entire amount of solder paste printed on the board adheres to the external electrodes of the chip component, so if the appearance of the solder paste is adjusted at the time of printing, the amount of solder as desired can be achieved. The external electrodes of the chip components can be coated, and variations in the external dimensions of the chip components after solder coating can also be reduced.

[Example] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First, as shown in FIG. 1, a substrate 11 made of a material to which molten solder is difficult to adhere, such as stainless steel, is prepared. Then, on the surface of this substrate 11, solder paste 14.15 is printed in a matrix shape using a stencil or the like, corresponding to the external electrodes 2.3 of the chip capacitor l explained in FIG. 6, for example.

Next, as shown in FIG. 2, the external electrodes 2 and 3 of the chip component 1 are aligned with the printed solder paste +4.15, respectively, and the chip capacitor l is placed on the substrate 11. In this state, the chip capacitor 1 is connected to the solder paste 1
Due to the viscosity of 4.15, the substrate l! will be affixed to. Board 11
is placed in a reflow oven (not shown) and heated to melt the solder pastes 14 and 15 printed on the substrate II. As a result, the solder pastes 14 and 15 become molten solder, and as shown in FIG. 3, the solder pastes 14 and 15 completely adhere to the external electrodes 2 and 3 of the chip component 1 due to their wetting action, respectively. This is because the substrate 11 is made of stainless steel to which molten solder does not adhere.

Thereafter, the chip capacitor l with solder attached to the external electrode 2.3 is placed in a tall and deep oil container 17 containing oil 16 inside, as shown by arrow A in FIG. Pour through the opening 18.

A heater 19 is disposed on the upper outer periphery of the oil container 17 near the opening 18 thereof. This heater 19 heats the oil I6 in the upper part of the oil container 17 to a temperature of 240° C. to 260° C. at which the solder melts. As a result, the upper part of the oil container 17 becomes a high temperature part 21, and the lower part thereof is continuous with a low temperature part 22 having a temperature of about 90°C.

Due to the above temperature distribution of the oil 16 in the oil container 17,
The chip capacitor l placed in the oil container 17 is
In the process of falling through the high temperature section 21, the solder adhering to the external electrodes 2 and 3 melts again. Then, as shown by arrow A3 in FIG.
6, the solder film is formed into a uniform solder film by applying pressure from the surroundings.

Thereafter, when the chip capacitor l reaches the low temperature part 22 of the oil container 17 shown in FIG. 4, the molded solder 2
3 cools down, solidifies, and falls into a saucer 25 arranged at the bottom 24 of the oil container 17. When a certain amount of chip capacitor I is collected in this saucer 25, chip capacitor 1
The saucer 25 containing the oil is taken out from the oil container 17.

In this way, the external electrodes 2.3 of the chip capacitor 1
A solder film can be uniformly and easily formed on the surface.

In the above embodiment, a chip capacitor l is placed in hot oil.
The solder adhered to the external electrodes 2.3 of the chip capacitor I was immersed and the solder adhered to the external electrodes 2.3 of the chip capacitor I was remelted and formed into a constant film thickness. It is also possible to remelt the solder adhering to the external electrodes 2.3 and mold them as described above.

Furthermore, cooling of the chip capacitor 1 after forming the solder film can also be performed using a low-temperature atmosphere.

The present invention can be applied not only to chip capacitors 1 but also to solder coating of external electrodes of chip components such as chip resistors and chip inductors.

[Brief explanation of the drawing]

1, 2, 3, 4, and 5 are process explanatory diagrams of an embodiment of the solder coating method for chip components according to the present invention. The perspective view and FIG. 7 are explanatory diagrams of a conventional solder coating method for chip components. l...Chip capacitor, 2, 3 - External electrode, II
...Substrate, 14.15...Solder paste, 1
6... Oil, 17. Oil container, 18... Opening, 1... Heater, 21... High temperature part,
22...Low temperature part, 23...Solder, 24.
··bottom. Patent Applicant: Murata Manufacturing Co., Ltd. Agent: Patent Attorney: 1 person (including the above) Figure 1 Figure 2 Figure 4 Figure 5-1 Figures 6 and 7

Claims (2)

[Claims] (1) A solder coating method for chip components in which the external electrodes of the chip components are coated with a solder film, in which solder is attached to the external electrodes of the chip components, and then the chip components are suspended in a gas or liquid. A method of solder coating a chip component, comprising heating and melting solder attached to an external electrode of the chip component, and then cooling the chip component. (2) A solder coating method for chip components in which the external electrodes of the chip components are coated with a solder film, in which a substrate to which molten solder is difficult to adhere is prepared, and the surface of this substrate is coated with the external electrodes of the chip components. Print a solder paste, align the external electrodes of the chip components with the printed solder paste, place the chip components, and heat the board to melt the solder paste and adhere the solder to the external electrodes of the chip components. Then, the solder attached to the external electrode of the chip component is heated and melted while the chip component is floating in a gas or liquid, and then the chip component is cooled. Coating method.