JPH0929478A - Foam solder and method for slightly sticking material to foam solder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct soldering having reliability by uniformly and slightly applying materials which are either inorg. matter or org. matter and are solid at ordinary temp. on the surface of foam solder having a flat surface. SOLUTION: The materials solid at ordinary temp., i.e., boric acid, calcium carbonate, lead oxide, etc., as the inorg. matter and mierstic acid, stearic acid, tartaric acid, etc., as the org. matter are previously uniformly applied on the surface of the foam solder. These materials hinder the contact of the foam solder with each other and, therefore, the metallic solid diffusion does not arise and the adhesion of the foam solder with each other does not arise. Good slipperiness is thus obtd. The materials are uniformly and slightly stuck on the foam solder if a soln. prepd. by dissolving these materials into a solvent is thinly applied on the surface of the foam solder and the solvent is allowed to evaporate. The good slipperiness is obtd. and the good solderability is attained without hindering an automatic supplying device without adhesion of plural sheets to each other even if plural sheets of the foam solder are superposed on each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam solder used for soldering electronic parts and electronic equipment.

[Prior art]

There are various types of foam solders, such as a circle, a rectangle, and a washer, depending on the shape of the soldering portion, and their manufacture is performed by punching a band-shaped solder with a press.

Since this foam solder can be soldered only by placing it on the soldering part and heating it together with the soldering part, it is economical because an expensive printing device such as solder paste is not required. Also, since the size of the form solder is constant, not only can a fixed amount of solder be supplied to all the soldering parts, but also solder with excellent reliability that the solder will always adhere to the place where the form solder is placed. It can also be done.

A relatively large form solder manufactured by a solder maker, for example, a circular form solder having a diameter of 50 mm or more used for pre-plating an IC wafer is stacked in a cylindrical container and delivered to a user. . The large foam solder delivered in this way is adsorbed one by one from the cylindrical container by the adsorption device and taken out by the user. After placing it on the IC wafer, it is treated like hydrogen or hydrogen / nitrogen mixed gas. Solder plating is performed on the wafer by heating in a different active atmosphere to melt the foam solder.

Also, a small foam solder, for example, a diameter of 10 mm used for soldering a head pin and an IC chip.
The following circular foam solders are delivered to users in polyethylene bags or plastic containers. When such a small foam solder is used by a user, it is aligned with a parts feeder and then sequentially sucked with air tweezers to be automatically supplied to a soldering part.

[0006]

By the way, when a large foam solder housed in a cylindrical container is adsorbed one by one with an adsorbing device and is to be taken out from the container, the conventional foam solder is taken out in a state in which a plurality of sheets are adhered. And
There was a case where an excessive amount of foam solder was placed on the IC wafer. If a plurality of foam solders are placed on an IC wafer and melted as it is, a large amount of solder will adhere to the IC wafer, which will not function properly when configured as an electronic component, It will cause defects that will not function at all.

[0007] Further, even a small foam solder contained in a polyethylene bag or a plastic container may have a plurality of foam solders attached thereto. When a plurality of foam solders are completely overlapped and adhered, a large amount of solder adheres to the soldered portion, which causes a defect in the electronic component. Further, if the foam solders partially overlap with each other, the shape becomes large and the foam solders cannot pass through the traveling path, which hinders automatic supply. Therefore, the form solder must never adhere to each other.

Further, the foam solder is often aligned and supplied by an automatic supply device such as a parts feeder and a hopper at the time of use. When the foam solder is supplied by the automatic supply device, the foam solder moves while sliding on the traveling path of the automatic supply device, and therefore should not be caught in the middle of the traveling path. However, the conventional foam solder is not slippery and often stops running on the road of the automatic feeder, or it runs while overlapping even if the foam solders do not completely adhere to each other, obstructing the running of other foam solders. Was sometimes.

The present invention, even if stacked in a cylindrical container or stored in a polyethylene bag or a plastic container,
The foam solder never sticks to each other, and even if it doesn't stop running in the automatic feeder or hinder the running of other foam solders, it prevents lubrication and adhesion on the surface of the foam solder. It is to provide a method of attaching a substance.

[0010]

[Means for Solving the Problems] The inventors of the present invention conducted extensive research into the causes of adhesion of foam solders and the causes of non-slippage. As a result, it was found that the cause of the adhesion of the foam solders was that the surface of the foam solders was very clean. In other words, if a large number of foam solders with clean surfaces are stacked in a cylindrical container or stored in a closed polyethylene container or plastic container, the weight of the foam solder placed on top of each other Because it will be crimped. The crimping is that the soft solders are adapted to each other and completely adhered to each other, and then lead or tin in the solder diffuses solidly and adheres more strongly when a time passes in the adhered state.

The reason why the foam solder does not slip easily is that the surface is still clean. In other words, a foam solder with a clean surface has lead and tin metal exposed on the surface that is hard to slip, and this metal is caught on the running path of the automatic feeder and other foam solders and hinders the sliding of the foam solders. Is.

It has been conventionally known that if the surface of the foam solder is not in a clean state but is in an oxidized state, the foam solder does not adhere to each other or become slippery. When the surface is oxidized, the oxide film interferes with the soldering process and hinders the solderability. Therefore, the inventors of the present invention do not cause solid diffusion between the foam solders while keeping the surface of the foam solders clean, and prevent lead or tin from directly contacting the running path of the automatic feeder or the foam solders. The present invention has been completed by focusing on the fact that the above-mentioned inconvenience does not occur.

The present invention is a foam solder having a flat surface, in which a small amount of a substance that is solid at room temperature is uniformly applied to the surface of the foam solder, and is also solid at room temperature. The substance is dissolved in a solvent to form a substance solution, the wetting material is impregnated with the substance solution, and the substance solution is applied to the surface of the foam solder with the wetting material. It is a method of depositing a trace amount of the substance on the surface of the foam solder by vaporizing the solvent so that the trace amount of the substance is uniformly deposited on the surface of the foam solder.

The substance used for the foam solder of the present invention may be any substance as long as it is solid at room temperature. Examples of inorganic substances include boric acid, calcium carbonate, calcium hydroxide, alumina white, aluminum silicate, tin oxide, lead oxide and the like.

The organic substances used in the foam solder of the present invention include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, behenic acid, oxalic acid, malic acid, succinic acid, tartaric acid, citric acid and benzoic acid. , Isophthalic acid, fumaric acid, etc. are suitable.

When the above-mentioned inorganic substance or organic substance has a solderability, that is, an active action, it can exhibit excellent solderability at the time of soldering. A very small amount will not hinder soldering. However, when an activator is added to a substance having no activator, the solderability can be improved. The activator used here is trinonylamine hydrobromide, 2-ethylhexylamine hydrobromide, phenylimidazole, benzotriazole, phenyltetrazolethiol, 2,3 dibromonopropanol, 1.1.2. 2 tetrabromoethane, 1.6 dibromoethane and the like.

In the foam solder of the present invention, the state in which the substance adheres to the surface is a fine powder state or a thin film state, but it is the fine powder state that improves the slipperiness.

In the method of depositing a substance on the foam solder of the present invention, the substance is dissolved in a solvent, but if the solvent used at this time does not have good wettability with respect to the solder alloy, the substance is evenly distributed. Cannot apply a small amount. Therefore, the solvent used has good wettability with respect to the solder alloy. However, when the solvent that dissolves the substance is difficult to wet the solder alloy, it is advisable to mix it with a solvent having better wettability.

The wetting agent used in the method of applying the substance of the present invention may be any one that can be impregnated with a liquid. A convenient wetting material for use in the present invention is sponge, brush, cloth or the like.

[0020]

[Function] When a solid substance is uniformly applied to the surface of the foam solder at room temperature, the substance interferes with the contact of the foam solder with each other, so that the metallic solid does not diffuse and the foam solder does not adhere. Not only that, the slipperiness is improved. Further, when a solution of a substance that is solid at room temperature in a solvent is thinly applied to the surface of the foam solder, and then the solvent is volatilized, a small amount of the substance uniformly adheres to the surface of the foam solder.

[0021]

[Examples and Comparative Examples]

Example 1 1 g of inorganic boric acid is dissolved in 10 g of methanol as a solvent to prepare a substance solution of 1.7 g of trimethyl borate.
Since trimethyl borate does not have very good wettability with respect to the solder alloy, it is mixed with 100 g of hexane, which is a solvent with good wettability with respect to the solder alloy. The sponge, which is a wetting material, is impregnated with the mixed solution. A circular foam solder is passed through a portion where the two sponges are combined, and the mixed solution is applied to the surface of the foam solder. The foam solder is a Pb-5Sn alloy for an IC wafer having a diameter of 50 mm and a thickness of 0.2 mm. The foam solder coated with the mixed liquid is naturally dried to volatilize the solvent and hexane. At this time, the trimethyl borate remaining on the foam solder is hydrolyzed by the moisture in the air to return to boric acid. Boric acid adhered to the surface of the dried foam solder in the form of fine powder so that it could be finally visually discerned. When 200 sheets of foam solder having boric acid adhered to the surface in this manner were placed in a cylindrical container and left for 10 days and then taken out by an adsorption device, none of them adhered and were taken out at all. Also, place this foam solder on the IC wafer to
When heated in a nitrogen-mixed gas active atmosphere furnace, soldering defects such as dewetting and unsoldered solder did not occur.

Example 2 1 g of organic stearic acid was added to 100 parts of isopropyl alcohol, which is a solvent having good wettability with respect to a solder alloy.
Dissolve in g. The substance solution is applied to the surface of the foam solder in the same manner as in Example 1. The foam solder here is a 63Sn-Pb alloy for a head pin having a diameter of 2 mm and a thickness of 0.1 mm. The foam solder coated with the substance solution is naturally dried to volatilize isopropyl alcohol. When the surface of the completely dried foam solder was observed with a microscope, adhesion of white crystals was observed. The foam solder with the stearic acid adhered to the surface in this way was put in a polyethylene bag, the internal air was evacuated and sealed, left for 10 days, and then placed in a parts feeder for automatic supply. The solder ran smoothly without stopping running on the way and overlapping with the form solder. When this foam solder was installed between the head pin and the transistor and heated in a reflow furnace in a hydrogen atmosphere, complete solder joining was achieved.

Comparative Example 1 After producing a foam solder having the same shape and alloy composition as in Example 1, the foam solder was placed in a cylindrical container without any treatment on the surface, left for 10 days, and then taken out by an adsorption device. As a result, many of them adhered to each other by the foam solder, and they were taken out in a state where a plurality of sheets were stacked on the adsorption device.

Comparative Example 2 After producing a foam solder having the same shape and the same alloy composition as in Example 2, the foam solder was put in a polyethylene bag without any treatment on the surface, air was removed from the inside, and the container was left for 10 days. After that, when automatic supply was performed with a parts feeder, it was found that a plurality of sheets overlapped with each other, or a plurality of sheets partially adhered to each other and the traveling stopped halfway.

[0025]

As described above, since the foam solder of the present invention has a trace amount of substance attached to the surface,
Form solder does not cause solid diffusion,
Even if they are stored in a container in a stacked state, not only will multiple pieces never adhere, but since the non-slip metal is not exposed on the surface of the foam solder, the slipperiness will be good and it will hinder the automatic feeder. There is no such thing. In addition, the method for applying a trace amount of a substance to the foam solder of the present invention dissolves the substance in a solvent to form a substance solution, impregnates this with a wetting material, and then coats it on the foam solder. It is possible to attach a very small amount of substance to, and even if the substance has no solderability, it does not adversely affect the soldering. Therefore, the foam solder obtained by the method of the invention can be reliably soldered.

Claims (4)

[Claims] 1. A foam solder having a flat surface, characterized in that a small amount of a substance that is solid at room temperature is uniformly applied to the surface of the foam solder. 2. The foam solder according to claim 1, wherein the substance is one of an inorganic substance and an organic substance. 3. The foam solder according to claim 1, wherein the substance contains an activator. 4. A substance which is solid at room temperature is dissolved in a solvent to form a substance solution, a wetting material is impregnated with the substance solution, and the substance solution is applied to the surface of the foam solder with the wetting material to obtain a foam. A method for adhering a trace amount of a substance to a foam solder, which comprises vaporizing a solvent of a substance solution applied to a surface of a solder to evenly attach the trace amount of the substance to the surface of the foam solder.