JPH02217193A - Indium series powdery solder - Google Patents

Abstract

PURPOSE:To enable use with rolling reduction at room temp. without any heating by blending the specific ratios of indium, tin and lead to make powdery solder. CONSTITUTION:Powder mixed material composed >=95wt.% of total contents of indium, tin and/or lead, and mixing ratio of these three components is 15-85wt.% indium, 15-85wt.% tin and/or lead is used to the powdery solder and a circuit pattern is formed on a circuit substrate. This is unnecessary to heating, and by pressurizing with roll, etc., diffusion among the powder particles is developed and the powder particles are mutually joined. In the case of containing below 15% indium, this can not be diffused under room temp. rolling reduction and exceeding 85% indium, this can not be pulverized. Blending ratio of thin is desirable to be >=35% and that of lead is desirable to be <=50%. This is unnecessary to heating and melting, and can be used with the rolling reduction at the room temp. and as this is powdery state, the treatment is easy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an indium-based powder solder used for forming circuits on printed circuit boards.

[Conventional technology]

Solder has long been used as a soldering material for metal materials, electronic components, etc. Solder includes solid solder in the form of a rod or thread, as well as powdered solder. Solid solder includes, for example, indium (In
), which is used in micro-soldering to make minute connections between semiconductor elements and conductors. Solid solder is used either by melting it and placing it on the object to be soldered, or by melting it and then dipping the object to be soldered into it. On the other hand, powdered solder is used in the form of a paste by kneading it with a highly viscous vehicle containing flux or the like. Typical usage examples of paste solder are:
Chip mount method This is a method of soldering chip components on a mounted board. This method involves applying solder paste to the necessary parts of the circuit pattern of an IC board, etc. using a screen printing method, mounting the chip components, and then reflowing the chip components. This is a method of welding the circuit pattern with solder.

In this way, conventionally, whether powdered solder or solid solder is used, the desired welding strength and conductivity have been secured by melting the solder once.

Conventional indium-based solder is generally made of indium (
Taking advantage of the property that In ) has a low melting point (156°C), S
By adding In to a normal solder alloy composition containing one or more of n, Pb, Ag, etc., the melting point of the solder is lowered, and at the same time, an oxide film is not formed on the metal surface by heating. It is something to do. Note that there are some usage examples in which the wettability of indium to glass and the like is improved by taking advantage of the good wettability of indium.

[Problem to be solved by the invention]

As mentioned above, when using conventional solder, 200
There is the trouble of having to heat it once to ~400°C and melt it. From the perspective of mounting electronic components,
This brings about the problem that the mounted components are unavoidably affected by heat. Even though the addition of indium has made it possible to melt at low temperatures, the high temperatures described above still form an oxide film on the surface of the base material that reduces solder wettability, resulting in poor solder yield. Leaving you with concerns.

Therefore, in view of the above-mentioned problems, it is an object of the present invention to provide an indium-based powdered solder that can be used in powder form without being heated and melted, and can be diffused at room temperature and pressure.

[Means to solve the problem]

In order to solve the above-mentioned problems, the indium-based powder solder according to the present invention consists of indium, tin, and/or lead at 95-t% or more of the total composition, and the mixing ratio of these three components is set to 15% of the total composition. By setting the content to 85-t% and 15 to 85 inch% of tin and/or lead, the powder is in powder form and can be diffused under pressure at room temperature.

In the indium-based powder solder according to the present invention, 95 wt% or more (including 100 wt%) of the total composition is the above-mentioned 3.
It must consist of indium, tin and/or lead in the mutual proportions. This is because if the amount of components other than the above three components exceeds 5 wt%, diffusion under normal temperature and pressure will not occur. Therefore, the indium-based powder solder according to the present invention has a power of 0.5 to 5w.
It can contain silver within a range of t%. Addition of silver facilitates powdering. Furthermore, it also contributes to increasing electrical conductivity. In addition, bismuth and antimony are added at 05~5w.
It may also include t%.

As seen above, in the indium-based powder solder according to the present invention, it is necessary that indium accounts for 15 to 85 wt % in the blending ratio of the three components. When indium is less than 15wt%, it cannot be diffused under normal temperature and pressure, and when indium exceeds 85iyt%,
This is because it cannot be powdered.

In the mixing ratio of the above three components, the mixing ratio of tin is 3
It is preferable that it is 5 wt% or more, and the blending ratio of lead is 5 wt% or more.
It is preferable that it is 0ivt% or more.

Indium-based powdered solder obtained by a non-oxidizing atmosphere powdering method (vacuum powdering method), which will be exemplified later, has an unoxidized surface and is therefore highly active and is preferably used. This is because when the blending ratio of is increased, diffusion occurs even without reduction, making it easier for the powder to coagulate.

It is sufficient that at least one of tin and lead is blended within the range of the above-mentioned blending ratio, but even when both are blended together, it is necessary that the above-mentioned blending ratio is satisfied. When both are used together, 5n-P is used as the raw material.
(b) It may be blended in the form of a eutectic alloy. The weight ratio of both in the eutectic alloy is 63 parts tin:37 parts lead.

Powderization can be performed in the same manner as conventional powdered solder. Therefore, various known powdering methods such as atomization can be used. Further, when obtaining powder with a large particle size, it is also possible to form the molten metal into powder by dropping it from a high place and passing it through a mesh provided in several stages. However, with these methods, a thin oxide film is formed on the surface of the powder particles, which may reduce surface activity. Therefore, if high surface activity is desired, use a non-oxidizing atmosphere that does not easily form a surface oxide film. Powdering method (vacuum powdering method)
It is better to adopt The vacuum powderization method is, for example, a method as shown in Figure 3. That is, a solder alloy is melted in a melting furnace 1, and the molten solder alloy is dropped through a nozzle 2 onto a high-speed rotating disk 4 in a vacuum tank 3. The '/'g molten solder alloy is scattered toward the inner wall surface of the vacuum tank 3 by the centrifugal force of the high-speed rotary plate 4, solidifies, and becomes powder. The obtained powdered solder 5 is taken out from the bottom of the cone-shaped tank 3. In the figure, 6 is valve 7
The outlet is equipped with a To create a vacuum inside tank 3,
This is to prevent oxidation of the solder alloy. In this case, if necessary, after creating a vacuum, the inside of the tank may be replaced with Ar gas or the like. The particle size of the solder alloy is appropriately set depending on the application, but the average particle size is generally 500 μm or less, and depending on the application, it may be on the order of several 1.

As will be described later, in order to diffusion bond individual powder particles under pressure at room temperature, it is necessary to use a material that is highly malleable and diffuses without being affected by the oxide film, allowing the powder particles to bond to each other. Requires metal. Diffusion phenomenon occurs due to the factors of heat, pressure, and time, and can be seen in most metals, but metals such as gold and indium that can undergo diffusion by applying a slight pressure at room temperature There are only a few. In this invention, in order to further reduce costs, relatively inexpensive indium is used.

[For production]

15-85wt of indium is added to the normal solder alloy composition.
%, it is easy to powderize the solder, and the obtained powdered solder causes diffusion when pressurized at room temperature.
The powder particles bond together and become electrically conductive.

Although the indium-based powder solder according to the present invention is in powder form, it can be used for forming circuit patterns on printed circuit boards in the same way as conventional paste solder without being made into a paste. In this case, heating is not required. By applying pressure with a roll or the like instead of using a roll, it is possible to cause the powder particles to diffuse, bond them to each other, and provide conductivity. Specifically, this indium-based powdered solder is placed on a board as a powder to draw an electric circuit, and then the powdered solder is pressed at room temperature with a pressure that does not destroy the board, and the powdered solder is individually separated. By crushing and stretching the powder particles, the powder particles are brought into close contact with each other and integrated by promoting diffusion. It goes without saying that in addition to the circuit formation described above, it can also be used for ordinary soldering purposes.

The uses of the indium-based powder solder according to this invention are as follows:
Not limited to the above. For example, it can be used for surface heating elements, indoor antennas, electromagnetic shields, antistatic materials, etc. The operating temperature is not limited to room temperature either.

〔Example〕

In the following, the indium-based powder solder according to the present invention will be explained in detail with reference to Reference Examples, Examples, and Comparative Examples.

Below, we first looked at the effect of indium content on powdering.

Reference Examples 1 to 8 In the In-3n system, the indium solders of Reference Examples 1 to 8 were packaged while changing the amount of indium to see whether powdering could be achieved. On each side, the metals other than the metal are 2 wt% silver and the balance tin. Powderization was performed using the apparatus shown in FIG. The particle size of each of the obtained solders was under 95 μm.

The results of powdering are shown in Table 1-1.

Reference Examples 9 to 15 In the In-Pb system, indium-based solders of Reference Examples 9 to 15 were manufactured while changing the blending amount of indium,
I looked to see if it could be made into powder. In each case, the metal other than indium was 2 wt% silver, and the balance was lead. Powderization was performed using the apparatus shown in FIG. The particle size of each of the obtained solders was under 90 μm.

The results of powdering are shown in Table 1-2.

From the results in Table 1, in the case of indium-based alloys whose powder particle surfaces are not oxidized, it is impossible to powderize the In-3n-based alloy when the blending ratio of indium is 70 wt% or more, and the In-Pb-based alloy It can be seen that it is impossible to powder an alloy when the blending ratio of indium is 55 wt% or more.

Examples 1 to 9, Comparative Examples 1 to 8 Next, Example 1 looked at the amount of indium and diffusivity.
-9 and Comparative Examples 1-8 will be explained.

Aluminum thin plate (thickness 0゜07mm) on epoxy resin substrate
), cut out a rectangular groove measuring 35 x 2 + u, and fill it with epoxy resin adhesive (Cemedine Hi-Quick C, a two-component room temperature curing type manufactured by Cemedine ■). Example 1 with solder alloy composition
~9. Sprinkle each powdered solder of Comparative Examples 1 to 8, and after the adhesive has hardened, peel off the aluminum thin plate and place it vertically on the board.
A rectangular solder powder band with two horizontal cranes was formed. In this case, the solder of Example 1.5 was pulverized by the atomization method, and the other solders were pulverized using the apparatus 4 shown in FIG.

Since conductivity was not observed for any of the powders as they were, as shown in FIG. 2, a slight pressure (
At both ends of the roll axis (I: 1 weight 10 kg, total 20 kg)
was added, and the sample (substrate) 11 was pressed down. In the figure, 13 indicates solder before being rolled down, and 14 indicates solder that has been rolled down.

The conductivity after this pressurization was measured using a simple tester.

Table 2 shows the measurement results for pressure and electrical conductivity.

From the results in Table 2, the indium-based powdered solder of the present invention, which contains indium in the range of 15 to 85 wL%,
Although good conductivity was shown, Comparative Example 1.2 contains indium outside the above range, Comparative Example 3 contains indium with a component outside the tin/lead layer (zinc), and Comparative Example does not contain indium at all. Nos. 4 to 8 had poor or no conductivity, indicating that no diffusion occurred under normal temperature and pressure.

For reference, we looked at how the indium-based powder solder according to the present invention changed over time during actual use.

Examples 10 to 13 The indium-based powdered solder of Examples 10 to 13 containing 35 to 50 wt% of indium and having a particle size of less than 95 μm was pasted onto a substrate using a room temperature curing adhesive manufactured by Mitsui Toatsu Chemical@. Thereafter, it was pressed with a roll to obtain a substrate with a circuit as shown in FIG. Then, the resistance between A-8 was measured using a simple tester immediately after manufacture, 18 days later, and 25 days later. The measurement results are shown in Table 3 along with the solder alloy composition, circuit thickness, etc.

(2) As shown in Table 3, all of the indium-based powder solders of the Examples have small resistance changes over time and can be suitably used as circuits.

〔Effect of the invention〕

Since the indium-based powder solder according to the present invention is configured as described above, it can be used at room temperature without being heated and melted, and there is no problem with conductivity even when used in this way.

In particular, the indium-based powder solder according to the present invention is
Since it is in powder form, it has the following effects. In other words, the shape when used can be freely developed, such as thick and thin, straight curved, etc. It can be placed even on uneven parts or holes. It is easy to transport by air transport, etc. Since the surface area increases, surface activity increases, wettability with other objects is good, and powder particles tend to aggregate (adhere). It is difficult to create a bridge in a supply hopper. Can be melted at low temperatures when used by reflow. When the particle shape is spherical, the powder particles have the same shape no matter how they are placed, so the placement position is stable, and they are easily crushed uniformly by external force, improving the diffusion effect.

[Brief explanation of the drawing]

FIG. 1 is a simplified cross-sectional view showing an apparatus for manufacturing powdered solder;
FIG. 2 is a side view showing an example of the use of the indium-based powder solder according to the present invention, and FIG. 3 is a plan view showing a circuit package formed using the solder according to the embodiment of the present invention. 11... Board 12... Roll 13... Solder before rolling 14... Solder agent after rolling Patent attorney Takehiko Matsumoto

Claims (1)

[Claims] 1. 95 wt% or more of the entire composition consists of indium, tin and/or lead, and the mixing ratio of these three components is 15 to 85 wt% indium and 15 to 85 wt% tin and/or lead. Indium-based powdered solder is powdered and can be diffused under pressure at room temperature. 2. The indium-based powder solder according to claim 1, wherein the blending ratio of tin is 35 wt% or more. 3. The indium-based powder solder according to claim 1 or 2, wherein the blending ratio of lead is 50 wt% or more. 4. The indium-based powder solder according to any one of claims 1 to 3, containing 0.5 to 5 wt% of silver.