JPS6390194A - Parts mounting method - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a component mounting method commonly used when performing so-called reflow soldering.

[Summary of the invention]

The present invention relates to a component mounting method, in which the top surface of solder supplied by immersion in or contact with molten solder is polished and mounted, thereby making it possible to perform good mounting with ordinary solder.

[Conventional technology]

When performing so-called reflow soldering, solder material is placed on the land that connects to the component on the board, the component is mounted on top of it, and then inserted into a reflow device to melt the solder and perform soldering. . In this case, so-called cream solder has conventionally been often used as the above-mentioned solder material.

That is, in FIG. 3A, the land (
Apply cream solder (32a) to 31a), (31b), and (31c) by screen printing, etc.
) (32b) (32c) are provided, and the component (33) is further mounted thereon. In this state, it is inserted into a reflow device and soldered.

However, in that case, when heating is started in the reflow apparatus, the cream solder (32a) to (32c) described above first melts, and since the viscosity of the melted cream solder (32) is low, it is shown in FIG. This melted cream solder (32) flows out of the lands (31a) to (31c). When further heated in this state, the solder (34) in the cream solder (32) melts (C) L,
At this time, the surface tension of the solder (34) is high and the substrate (30
) is coated with solder resist, so solder (34
) are on the lands (31a) to (31c) or on the parts (3
I try to return to the connection part 3), but I can't return everything. For this reason, as shown in the same figure, the so-called solder ball (35)
Or, as shown on the right side of the figure, land (31b) (3
1c) are close to each other, a bridge (
36) may occur.

Therefore, in the past, steps such as cleaning the substrate (30) and cutting the bridge were required after the above-mentioned steps.

Furthermore, when using the cream solder described above, the cream solder itself is expensive, easily deteriorates in the air, and its viscosity easily changes depending on temperature, etc., making it difficult to stably supply the solder to the land. There are problems such as the need to mount parts and process the flow within a short period of time after supply.

Furthermore, there are two methods for supplying cream solder: the so-called printing method and the one-dispenser method. However, in the so-called printing method that uses a screen, the screen must be changed every time the board is changed, and in the one-dispenser method, there is control that corresponds to the board. In addition to having to create data, there were also problems such as extremely low household capacity.

On the other hand, there is a method of supplying solder by immersing or contacting a substrate with a solder resist in molten solder other than the land, but in this case, since the surface tension of the solder is high,
As shown in FIG. 4, the solder (34) on the land (31) has a hemispherical shape, making it difficult to place the component when mounting the component. In addition, if you try to temporarily fix parts with adhesives, etc., the temporary fixing ratio is low for parts with a large number of electrodes, such as flat package ICs, but the ratio increases for parts with a small number of electrodes. This is not a realistic method as it would double the number of steps.

[Problem that the invention seeks to solve]

As mentioned above, with conventional technology, when cream solder is used, there is a high risk of solder balls and bridges occurring, and with normal solder, parts cannot be mounted well. .

[Means for solving problems]

The present invention provides lands (1a) (
1b), the solder (3a) (3b) is supplied by dipping or contacting the board with the molten solder, the upper surface of the supplied solder is polished, and the component (5) is placed on the polished solder. This is a component mounting method that performs mounting.

[Effect]

According to this, components can be mounted using ordinary solder, and good flow soldering can be performed stably and inexpensively.

〔Example〕

FIG. 1 shows a process diagram. In this figure, land (la)
The substrate (2) provided with (lb) is immersed in or brought into contact with molten solder, and each land (la
) Solder (3a) (3b) is supplied on (lb). The solder (3a) (3b) supplied here has a hemispherical shape.

This solder (3a) (3b) is polished,
The thickness of solder (3a) (3b) is 50 to 200μra
be reduced to a certain degree. By this, solder (3a) (3b)
The upper surface of the holder is flattened as shown in FIG.

Furthermore, flux (4) is applied to the entire surface of this substrate (2) as shown in FIG. Here, the flux (4) is preferably adhesive.

Then, the component (5) is mounted on the substrate (2) coated with the flux (4) as shown in the figure.

Therefore, in this mount, lands (1a) (1b)
Since the top surfaces of the upper solder (3a) and (3b) are flat, it is difficult for the component (5) to shift when mounted, and the adhesiveness of the flux (4) makes the component (5) ) is temporarily fixed.

Further, this substrate (2) is inserted into a reflow apparatus.

Therefore, in this case, the solder (3a) (3b) remains fixed until the melting point of the solder is reached and the land (la) (l
b) It does not flow out from above, and when it reaches the melting point, the surface tension of the solder causes it to form a land (la) as shown in the same figure.
(lb) and the connection point of part (5),
It will not flow out from the land (la) (lb).

In this way, parts are mounted and flow soldered, but the method described above uses ordinary solder, which is inexpensive, makes the supply of solder easy and stable, and prevents solder balls and pre-fuses from occurring. There's no fear. Furthermore, even if the state shown in the above-mentioned process diagrams A to C is left for some time, there is little risk of deterioration over time.

This allows the entire manufacturing process to be configured very well.

Furthermore, FIG. 2 shows an example of a beam flow device. In the figure, the substrate transport chain (11) is circulated, and this chain (
11) is a heated inert steam (1
2) is passed through the filled heating zone. A tank (14) containing an inert liquid (13) is provided at the bottom of this heating zone, and the above-mentioned inert vapor (12) is generated by heating with a heater (15) in this tank (14). Ru. Further, before and after the heating zone, there are provided cooling zones in which cooling coils (16) are arranged, whereby the liquefied inert liquid is returned to the above-mentioned tank (14).

As a result, the above-mentioned substrate (2) is heated by the inert steam (12) in the heating zone to the melting point of the solder (3a) (3b), and reflow soldering is performed.

By the way, in the above board (2), the large component (5)
Adhesives are sometimes used for stable fixation. In this case, since it takes a long time for the adhesive to harden naturally, rapid hardening is performed by heating with a heater or the like. However, in conventional so-called heaters, the substrate (
It is difficult to adjust the temperature to account for variations in heat capacity of the substrate (2) and the component (5), and there is a great risk of damage to the substrate (2) and the component (5).

Therefore, by curing the adhesive in the above-mentioned glue flow apparatus, the adhesive can be heated to a desired degree regardless of its heat capacity, and extremely good hard flowers can be produced.

Furthermore, in the above figure, by providing a tJV lamp (17) with less heat radiation on the entrance side of the heating zone, it is possible to further improve the curing of the adhesive by means of ultraviolet rays.

〔Effect of the invention〕

According to this invention, parts can be mounted using ordinary solder, and good flow soldering can be performed stably and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a detailed explanatory diagram of the present invention, FIG. 2 is a configuration diagram of an example of a beam flow device, and FIGS. 3 and 4 are diagrams for explaining conventional techniques. (Ia) (lb) is land, (2) is board, (3a
) (3b) is solder, (4) is flux, and (5) is parts. Breakthrough II /) Figure 1

Claims (1)

[Claims] Supplying solder to lands provided on the substrate by dipping or contacting the substrate with molten solder, polishing the upper surface of the supplied solder, and polishing the top surface of the supplied solder. A component mounting method that performs component mounting.