JP2003332509A - Method for manufacturing electric device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture efficiently an electric device of high reliability. <P>SOLUTION: Solder is stuck to leads 21 of all molded elements 10 in a state of products 15 being in process before the molded elements 10 are isolated. Superfluous solder (solder liquid) 25 is left between the leads 21 due to surface tension or the like. By jetting gas against the solder 25 in this state, the solder 25 between the leads 21 is removed. The solder 25 stuck to the lead 21 surface is not removed, so that a solder coating film 28 is formed on the surface of the lead 21 by curing the solder 25. Soldering is enabled at the same time to all the leads 21 of the plurality of molded elements 10, so that production efficiency is superior. The superfluous solder is not left between the leads 21, so that the electric device of high reliability can be obtained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder coating technique, and more particularly to a technique for solder coating the leads of an electric device.

[0002]

2. Description of the Related Art Conventionally, electric devices in which electric parts such as IC chips are sealed in a mold have been widely used. In such an electric device, a solder coating is usually formed on the surface of the lead. As a method of forming the solder coating, there are an immersion method and a plating method.

Of these, the dipping method is used for the work-in-progress of which leads of a plurality of mold elements are integrated by tie bars.
After cutting the tie bar to separate the mold elements, the mold elements are immersed in molten solder one by one and then pulled up.
This is a method of solidifying the molten solder attached to the lead surface by cooling.

Although the dipping method is easy, solder is likely to accumulate in the space surrounded by the leads and the tie bars, so that one mold element is processed at a time. Therefore, the production efficiency is low, and when the lead interval is narrow, solder may remain between the leads due to surface tension, and the leads may be short-circuited.

The plating method is a method in which the tie bar is not cut and a solder plating film is formed on the lead surfaces of all the mold elements of the work-in-process by electrolytic plating, and then the tie bar is cut to separate the mold elements. Production efficiency is high because multiple mold elements can be plated at the same time.

However, the plating method is not only higher in manufacturing cost than the dipping method, but so-called whiskers sometimes occur at the tips of the leads during the growth process of the plating. Moreover, it may cause a failure of the circuit board. Further, in recent years, it has been required to use a so-called lead-free solder that does not contain lead in consideration of environmental problems. However, when a lead-free solder coating film is formed by a plating method, manufacturing cost becomes particularly high.

[0007]

SUMMARY OF THE INVENTION The present invention was created in order to solve the above-mentioned disadvantages of the prior art, and an object thereof is to provide a technique for efficiently producing an electric device having no short circuit between leads. It is a thing.

[0008]

According to a first aspect of the present invention, which is made on the basis of the above problems, a solder coating is formed on the surface of the lead of a work-in-progress product in which leads of a plurality of mold elements are connected by tie bars. After that, cut the tie bar,
A method of manufacturing an electric device for obtaining a product of the molded element, comprising: attaching solder to the leads of all the mold elements of the work-in-progress, and then removing the solder existing between the leads. Is the way. The invention according to claim 2 is the method for manufacturing the electric device according to claim 1,
After immersing the leads of all the mold elements in the molten solder, pulling up the leads from the molten solder to attach the solder to the leads, and before the solder solidifies, hot air is applied to the solder. Is sprayed to remove the solder existing between the leads. The invention according to claim 3 is the method of manufacturing an electric device according to claim 2, wherein when the lead is pulled up from the solder, the lead is made vertical, and when hot air is blown to the solder, It is a method of manufacturing an electric device in which a portion to which hot air is blown is moved from above to below.
The invention according to claim 4 is the method for manufacturing an electric device according to claim 1, wherein a paste-like substance containing solder particles and a resin is used as the solder, and the paste-like substance is applied to the leads of the mold element. A method of manufacturing an electric device, which comprises applying the solder to the leads and then blowing gas onto the paste-like substance to remove the solder existing between the leads. A fifth aspect of the present invention is the method for manufacturing the electric device according to any one of the first to fourth aspects, wherein the lead surface has a film thickness after removing the solder existing between the leads. It is a method of manufacturing an electric device for forming a solder coating of 0.1 μm or more. The invention according to claim 6 is the method for manufacturing an electric device according to any one of claims 1 to 5, wherein the lead-free solder is used as the solder. The invention according to claim 7 is the method for manufacturing an electric device according to any one of claims 1 to 6, wherein the lead has a thickness of 100 μm or more. .

The present invention is configured as described above, and in the present invention, the tie bar of the in-process product is not cut,
Solder is attached to each lead of all mold elements. At this time, excess solder remains between the leads, but if gas is blown to the solder before the solder hardens, the solder remaining between the leads is blown away, but the solder adhering to the lead surface remains. After the solder attached to the surface of the leads is hardened and the tie bar is cut, the mold elements are separated and an electric device is obtained.

As described above, according to the present invention, since a plurality of mold elements can be soldered at one time and the leads are not short-circuited by the residual solder, the highly reliable electric device can be efficiently produced. You can Further, according to the present invention, since the solder is applied not by the plating method but by coating or dipping, the solder coating can be formed at a low cost using lead-free solder that does not contain lead.

When the leads are connected by tie bars, the solder is likely to accumulate in the space surrounded by the leads and the tie bar. In particular, after the work-in-progress is dipped in a solder solution composed of molten solder or the like, the solder solution is When it is pulled up from above, the solder liquid is likely to collect in the portion above the tie bar. Further, when the reinforcing member parallel to the lead is provided, the solder remains not only between the leads but also between the reinforcing member and the lead. Since excess solder is removed later, a short circuit between leads does not occur.

When the solder between the leads is removed, if the gas is blown to the leads of all the mold elements at the same time, the solder remaining between the leads can be blown off at once.
Further, if the nozzle that blows the gas onto the solder and the work-in-progress are moved relatively, the portion that blows the gas onto the solder moves, and the solder remaining between the leads can be gradually blown off. In this case, the nozzle may be moved while the work-in-process product is stationary, or the work-in-process product may be moved while the nozzle is stationary. Further, both the nozzle and the work-in-progress may be moved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a process for manufacturing an electric device according to the present invention will be described in detail below. Reference numeral 1 in FIGS. 2 and 3 indicates an example of a coating apparatus used in the present invention. This coating apparatus 1 has a solder bath 2 and a removing means 5. A solder liquid 25 made of molten lead-free solder (here, tin / bismuth alloy) is placed in the solder bath 2, and the solder is melted by a heating means (not shown) installed in the solder bath 2. Has been maintained.

The removing means 5 comprises the first and second nozzles 3 and 4.
And a blower 6. The first and second nozzles 3,
4 is an elongated shape such as a cylindrical shape or a prism shape.
They are horizontally arranged in parallel with each other at a predetermined interval. A heater is provided inside the first and second nozzles 3 and 4. The first and second nozzles 3 and 4 are connected to the blower 6 by a pipe 7, and when the blower 6 is started and an inert gas is sent to the first and second nozzles 3 and 4, the gas becomes first. , Are heated by the heaters inside the second nozzles 3, 4.

A plurality of holes are provided in a row at positions of the first and second nozzles 3 and 4 facing each other, and the air heated by the heater is at an intermediate position between the first and second nozzles 3 and 4. It is designed to be ejected from each hole toward. Reference numeral 15 in FIG. 1 indicates that the leads 21 of the plurality of mold elements 10 are tie bars 22,
It is an in-process product in a state of being connected by 23. here,
The tip ends of the leads 21 and the roots of the leads 21 are connected by tie bars 22 and 23, respectively.
A reinforcing member 24 connects the two and 23 to each other.

Each mold element 10 is provided with three leads 21 in a row, and the lead 21 at the center thereof is provided.
Are connected to a stage arranged inside the mold portion 16 of the mold element 10. A semiconductor chip is mounted on the stage, and the other two leads 21 are connected to the semiconductor chip by wire bonding. Here, the lead 21, the tie bars 22 and 23, the reinforcing member 24, and the stage described above are made of copper.

A method of manufacturing the electric device of the present invention using this work-in-progress 15 will be described. Since no solder coating is formed on the surface of the lead 21 of the work-in-progress 15,
The copper forming the lead 21 is exposed. In order to form a solder coating on the surface of the lead 21, first, the work-in-process product 15 is moved from another position onto the solder bath 2 of the coating apparatus 1 described above, and the lead 21 is directed vertically downward. It is made to stand still on the solder bath 2. FIG. 4A shows that state.

The work-in-process product 15 is lowered with the leads 21 facing vertically downward, and the leads 21 are dipped in the solder solution 25 as shown in FIG. 4B. At this time, the tie bars 22, 23 and the reinforcing member 24 are also immersed in the solder solution 25 together with the lead 21. Next, the work-in-process product 15 is pulled up from the solder solution 25 with the leads 21 facing vertically downward.

As described above, since the tips of the leads 21 are connected to each other by the tie bars 22, the solder solution 25 dripping from the top is collected in the tie bars 22, and the leads 21 are, as shown in FIG. 5 (c). The space and the space between the lead 21 and the reinforcing member 24 are filled with the solder liquid 25 accumulated in the tie bar 22. Reference numeral 39 in FIG. 5C indicates a work in progress 15
The voids formed in the solder liquid 25 attached to the are shown.

Here, the first and second nozzles 3 and 4 are fixed on the solder bath 2. Hot air is jetted from the first and second nozzles 3 and 4 in advance, and the work-in-process product 15 is further moved upward with the tips of the leads 21 facing vertically downward to fix the first and second fixed parts. When the nozzles 3 and 4 are passed from below to above, hot air is sequentially blown from the root of the lead 21 toward the tip thereof, and the solder liquid 25 between the leads 21 and between the lead 21 and the reinforcing member 24 becomes the upper end. Solder liquid 2 that was blown off from the bottom to the bottom,
5 drops into the solder bath 2. Reference numeral 38 in FIG. 5D indicates a droplet of the solder liquid that drops into the solder bath 2.

At this time, the solder liquid 25 is maintained in a molten state by being heated by the hot air, and the lead 21
The solder liquid 25 between the lead 21 and the reinforcing member 24 does not solidify. In a state after the work-in-process product 15 has passed between the first and second nozzles 3 and 4, the solder liquid is removed from between the leads 21 and between the leads 21 and the reinforcing member 24. The solder liquid 25 adhering to the surface remains. When the in-process product 15 in that state is naturally cooled, the solder liquid 25 adhering to the surface of the lead 21 is solidified, and a solder coating film having a film thickness of 0.1 μm or more is formed on the surface of the lead 21.

Reference numeral 30 in FIG. 5 (d) indicates a work-in-progress product in which the solder coating 28 is formed. In this work-in-progress product 30, between the leads 21 and between the leads 21 and the reinforcing member 24.
Since the solder between and is removed, a solder bridge is not formed. In addition, FIG. 6A shows a work-in-progress 1
5 before being immersed in the solder liquid 25, and
6B is a sectional view taken along line A, and FIG. 6B shows the work-in-process product 15 immediately after being immersed in the solder liquid 25.
4 is a cross-sectional view taken along the line AA of FIG. 5 (c) before passing between the four nozzles, and FIG. 6 (c) shows a work-in-process product 15 after passing between the first and second nozzles 3 and 4. It is the sectional view on the AA line of FIG.5 (d).

When the tie bars 22 and 23 are separated from the leads 21 of the work-in-process product 15 in which the solder coating 28 is formed, the tie bars 22 and 23 and the reinforcing member 24 are removed,
The mold element 10 is separated. Reference numeral 35 in FIG. 7 indicates a product (electrical device) of the molded element separated from the work-in-process product 15.

The case where the work-in-process product 15 is passed from the lower side to the upper side of the first and second nozzles 3 and 4 has been described above, but the present invention is not limited to this. For example, the work-in-progress product 15 is used as the first and second nozzles 3,
4 from the upper side to the lower side, or when the work-in-progress 15 and the first and second nozzles 3 and 4 are relatively moved in the horizontal direction, the first and second nozzles 3 are moved. It is also possible to pass between 4 horizontally.

In the above, the case where the in-process product 15 is gradually removed while passing through the first and second nozzles 3 and 4 has been described, but the present invention is not limited to this. For example, if the blower 6 is stopped and the work-in-process product 15 immediately after being pulled up from the solder liquid 25 is placed between the first and second nozzles 3 and 4, and the blower 6 is started, the lead 21 and The solder liquid between the lead 21 and the reinforcing member 24 can be removed all at once.

Further, although the case where the removing device 5 has two nozzles 3 and 4 has been described above, the number of nozzles is not particularly limited, and the removing device 5 has three or more nozzles. The present invention also includes a case where only one nozzle is provided and air is blown toward one surface of the in-process product.

The case where the work-in-process product 15 is dipped in the solder liquid 25 and the solder liquid is attached to the leads 21 has been described above, but the present invention is not limited to this.
The present invention also includes a method of attaching a solder liquid by a screen printing method. A process of manufacturing an electric device using the screen printing method will be described. First, solder particles and resin are kneaded to prepare a solder paste. Next, the solder paste is applied to all the leads 21 of the work-in-process product 15 shown in FIG. 1 by screen printing.

FIG. 8 shows the work-in-process 15 immediately after the solder paste 57 is applied by screen printing.
In this state, the surface tension of the solder paste 57 completely fills the spaces between the leads 21 and between the leads 21 and the reinforcing member 24 with the solder paste 57. The work-in-progress product 15 in that state is removed from the first and second nozzles 3 and 4 of the removing device 5 described above.
The solder paste 57 between the leads 21 and between the leads 21 and the reinforcing member 24 can be removed by passing the gap.

When using the above-mentioned solder paste,
If the resin in the solder paste is cured after the excess solder has been blown off, the solder paste is cured and a solder coating made of the cured solder paste is formed. When a thermosetting resin is used as the resin in the solder paste, the solder paste can be cured by heating. Further, when an ultraviolet curable resin is used as the resin in the solder paste, the solder paste can be cured by irradiation with ultraviolet rays.

Although the case of removing excess solder by blowing gas has been described above, the present invention is not limited to this. A metal cloth for removing solder, for example,
When a metal cloth made of copper fibers is applied with flux, and the metal cloth is pressed against the lead to which solder is attached while heating, the flux is activated by heating and the metal cloth gets wet. Since the solder becomes attached to the leads, the solder that remains on the leads remains, but the solder that remains due to the surface tension between the leads is adsorbed and removed by the metal cloth.

In short, the present invention includes all cases in which excess solder existing between the leads 21 and between the leads 21 and the reinforcing member 24 of the work-in-process product 15 in which the solder is attached to all the leads 21 is removed. Lead 21 and tie bar 2
Although the thicknesses of 2 and 23 are not particularly limited, if the thickness is 100 μm or more, the lead is not deformed in the step of attaching the solder liquid.

The metal forming the leads 21 and the tie bars 22 and 23 is not limited to copper, but various metals such as aluminum can be used. Moreover, the number of leads 21 of the molded element 10 is not particularly limited. The gas ejected from the nozzle is not limited to air, and various gases such as N ₂ gas can be used.

The type of solder is not particularly limited, but lead-free solder is preferable from the viewpoint of environmental problems. The lead-free solder used in the present invention is not limited to the tin / bismuth alloy, and various types such as tin / copper alloy and tin / silver alloy can be used.

[0034]

According to the present invention, the soldering is performed immediately after the mold sealing and before the semiconductor element is separated.
Soldering can be performed while the lead surface is not deteriorated and solder wettability is high. Even if the pitch between the leads is narrow, the excess solder is removed after soldering, so that the mold element does not short circuit. Since the present invention does not use the plating method but solders by coating or dipping, not only whiskers do not occur, but also a solder coating can be formed at low cost using lead-free solder.

[Brief description of drawings]

[Figure 1] Plan view of work in progress

FIG. 2 is a sectional view of a coating device.

FIG. 3 is a plan view of a coating device.

4A and 4B are views for explaining the first half of the step of forming a solder coating.

5C and 5D are views for explaining the latter half of the step of forming a solder coating.

6A to 6C: AA in the process of forming a solder coating
Line cross section

FIG. 7 is a plan view of an electric device.

FIG. 8 is a diagram illustrating another example of the step of forming a solder coating.

[Explanation of symbols]

10: Mold element 15 ... Work in progress 21 ... Lead 22, 23 …… Tie bar 25 ... Solder liquid (solder) 28 ... Solder film 35 ... Electric device 57 ... Solder paste (paste-like substance)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Furusato             10-13 Minamimachi, Hanno City, Saitama Prefecture Shindengen Industrial Co., Ltd.             Inside the company F-term (reference) 5F067 DC12 DD06

Claims (7)

[Claims] 1. A method for manufacturing an electric device for a work-in-progress product, in which leads of a plurality of mold elements are connected by tie bars, after forming a solder coating on the surface of the leads and then cutting the tie bars to obtain a product of the mold elements. A method of manufacturing an electric device, comprising: attaching solder to the leads of all the mold elements of the work-in-progress product, and then removing the solder existing between the leads. 2. After immersing the leads of all the mold elements in the melted solder, the leads are pulled out from the melted solder, the solder is attached to the leads, and before the solder is solidified. , Blowing hot air on the solder,
The method for manufacturing an electric device according to claim 1, wherein the solder existing between the leads is removed. 3. The lead is made vertical when the lead is pulled up from the solder, and when hot air is blown to the solder, the hot air blown portion is moved downward from above. Of manufacturing electric device of. 4. A paste-like substance containing solder particles and a resin is used as the solder, the paste-like substance is applied to the leads of the mold element to adhere the solder to the leads, and then the paste-like substance is applied. The method of manufacturing an electric device according to claim 1, wherein a gas is blown to the substance to remove the solder existing between the leads. 5. The electric device according to claim 1, wherein a solder coating having a film thickness of 0.1 μm or more after removing the solder existing between the leads is formed on the lead surface. Manufacturing method. 6. The method of manufacturing an electric device according to claim 1, wherein lead-free solder is used as the solder. 7. The method of manufacturing an electric device according to claim 1, wherein the lead having a thickness of 100 μm or more is used.