JPS5984962A - Electrically conductive hot-melt adhesive - Google Patents

Abstract

PURPOSE:To prepare the titled adhesive easily attachable to and removable from the work, having excellent adhesivity, and useful for electrical discharge machining, etc., at a low cost, by mixing a thermoplastic resin and wax with specific amount of silver powder, nickel powder and/or graphite powder. CONSTITUTION:The objective adhesive can be prepared by mixing (A) 100pts.wt. of a thermoplastic resin and/or a wax (preferably microcrystalline wax) with (B) 5-150pts.wt., preferably 10-60pts.wt. of silver powder, nickel powder and/or graphite powder (preferably the mixing ratio of silver powder to nickel powder is 1:0.5-1:3.5, the particle of silver powder is finer than nickel powder, and the mixing ratio of graphite powder to the other metallic powder is 1:1-1:5). EFFECT:Since the resin and wax can be dissolved easily and rapidly in an alkaline solution or organic solvent, the adhesive remaining on the surface of the work can be removed easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot melt type conductive adhesive used in electrical and chemical processing methods such as electrical discharge and electrolytic processing methods.

The above J: machining method involves adding two liquids, a machining tool (grinding wheel, electrode Y V, etc.) to the workpiece, electrical discharge,
This is done by applying electricity to a method called electrolysis.

Therefore, it is necessary to ensure that the workpiece and the support stand are in a state where electricity can be applied to the paste.

However, the paces 1~ currently in use have the following drawbacks.

B. Because it is thermosetting, it is necessary to remove the workpiece for chemical work, which reduces its longevity.

Mouth: It is troublesome to remove adhesive remaining on the surface of the removed workpiece.

C. In order to obtain good conductivity 11, it is necessary to increase the addition rate of silver powder, but as a result, the fluidity hN deteriorates and the thickness of the adhesive layer becomes uneven, making it difficult to perform high-precision processing. .

2. Because the adhesive layer cannot be made thinner, bases 1 to 1 are used, which is a waste of experience.

The present invention was devised to improve these points, and an object of the present invention is to provide a conductive adhesive that can be easily attached to and removed from a workpiece, has good adhesive performance, and can be used economically.

B. Process of development The inventor of the present invention mixed one or more powders of silver, nickel, zinc, etc. into various molten adhesives, and then cooled and mixed them with 21. (I was solidified and the conductivity ↑1 was measured with a tester.

The results showed that most of them showed no conductivity and could not be used with other conductive materials.

Next, some of the samples were heated to conductive work, 83 J
:Apply it to the base and the support base, press them together and roll them in a cold oven.

As a result, good electrical conductivity is produced between the two.

Next, the conductivity was examined by varying the blending ratio of the conductive powder.

It has been found that even with the current paste J, Rimo, which has a much lower weight ratio, sufficient electrical conductivity can be obtained in the bonded area by applying pressurizing conditions.

Furthermore, when the blending ratio of the conductive powder was low, the fluidity in the molten nourishing body was extremely good, and the thickness of the weld layer could be made much thinner and more uniform compared to the thermal effect paste 1-.

The reason for this is that when pressurized, the molten fujia protrudes outside, and the remaining base material particles come into contact with each other in the same flow direction. Kato 11
1 is determined.

Mouth! ＾Nari Kiso This invention was made through this discovery! , : The basic configuration will be explained next.

[Thermoplastic resin] All of the conventionally used resins such as (7), lac, rosin, EVA (ethylene vinyl acetate), and polyamide can be used.

[Microcrystalline wax] Various petroleum-based, animal-based, plant-based, and mineral-based waxes are used.

The important properties of adhesives, such as melting point, viscosity, and adhesive strength, can be freely adjusted by changing the resin, wax, or mixing conditions of the resin and wax.

[Conductive powder] Silver powder, nickel powder, and zinc powder can be used. Silver is preferable in terms of properties and stability, but it is expensive, so if cost 1- is a problem, inexpensive nickel powder is mixed and used.

However, since the conductivity of the adhesive changes over time due to the mixing of nickel, it is generally desirable to keep the weight ratio of nickel powder to less than twice that of silver powder. For example, silver 22) The weight ratio of the gel is
Preferably, the Nu range is 1:0.5 to 1:3°5.

Furthermore, for higher conductivity and lower aging deterioration, it is necessary that the particle size of the silver powder be smaller than that of the nickel powder. The reason for this is presumed to be that the small-diameter silver powder coats the nickel and contacts the phase U, and the contact resistance between the particles is much smaller than if the particle size relationship was reversed. This is thought to be because chemical changes on the particle surface are also significantly suppressed.

[Particle Size of Powder] In the adhesive of the present invention, the influence of the particle size of especially large particles is extremely large.

The reason for this is that the thickness of the adhesive layer, which adheres by pressing the bonded parts, is determined by the particle size of the particles on the side.

Therefore, if you want the thickness of the adhesive layer to be around 5 microns,
It is necessary to make the diameters of large particles similar, and micro A-
When desired precision in processing the goo, the diameter of the particles is desirably 5 microns or less.

On the other hand, the diameter of the silver particles is desirably from a few minutes of 1 m to several tens of meters.

Graphite powder is inexpensive and does not deteriorate over time, but it has an order of magnitude higher electrical resistance than silver powder or nickel. Therefore, when the machining current is low and the machining cost is severely restricted, it is used by mixing it with silver powder or a mixed powder of silver and nickel powder.

Mixture of graphite powder with metal powder [He, 21s1~
It is desirable that the ratio be within the range of 1:1 to 5:1 due to the balance between conductivity and conductivity.

[Mixing ratio] Inquire about whitening of the base material (J-nawara thermoplastic resin, wax, or a mixture thereof) and conductive powder (one or a mixture of two or more of silver powder, nickel, and graphite powder). .

If the former is 1001fn, but the latter is less than 5, the electrical resistance of the bonded portion will be extremely high, making it extremely difficult or impossible to obtain the continuity necessary for processing.

If the latter weighs more than 150%, the fluidity in the molten state will be low, making it difficult to obtain a thin layer with uniform thickness, and insufficient adhesive strength will be obtained.

Therefore, the blending ratio needs to be within the range of 5 to 1.50 parts of conductive powder per 100 weight of the base material, but considering conductivity, fluidity, adhesive strength, etc., it is 10 to 60 parts of conductive powder.
It is desirable that it be heavy.

This point is extremely significant compared to the current conductive silver paste, which has an appropriate silver content of 150% by weight or more.
It can be seen that it is curved.

Although the above is the basic structure of the present invention, small amounts of other substances such as plasticizers, antioxidants, etc. may be added. However, these additions are limited to the extent that they do not fundamentally affect the properties of the adhesive.

8. Effects of the present invention (a) Since the workpiece is of the Hola I/Mel type, the workpiece can be removed very easily and in a short time by simply heating it to 811 points or higher, and high workability can be expected.

(b) The basic materials resin and wax are alkaline solutions.
The adhesive remaining on the surface of the workpiece can be removed very easily since it can be easily and quickly applied with just one solvent.

(c) Since the blending ratio of conductive powder is significantly lower than that of current thermosetting green conductive pastes, it has high fluidity when melted. Therefore, variations in the thickness of the adhesive layer can be reduced, and less adhesive is used in high-ri'i processing, making it economical.

(e) Since the blending ratio of silver powder is low, it can be used for cheap (+lIi).

Next, an example will be explained.

[Example 11] C112x102x100 steel plates were bonded using the adhesive of the present invention and a conventional thermosetting conductive adhesive, and ten tensile test samples were prepared for each composition. Then, the following data was measured.

1. Electrical Resistance: The electrical resistance of the bonded portion and its average value using a Destar 2. Thickness of the layer at the bonded portion T: The thickness was measured using a micrometer, and the average value and the variation in thickness were determined.

3. Average breaking strength: Insu (by Ron type testing machine,
The tensile test was carried out at a speed of 0.01 mm per second.

The adhesion conditions for each adhesive were as follows.

1. Adhesive of the present invention: Apply to one end of a pair of steel plates heated to 150°G, overlap them as shown in Figure 2, and bond the joint (
1cm x 1cm) with a 200g weight to harden it.

2. Conventional type adhesive 2 Apply to the joint part at room temperature and overlap it to make the joint part (ICIIl x lcm) 200<
Heat at 1506C for 2 hours while pressurized with + to harden.

The results are shown in Table 1, and the following can be seen from this table.

1. The adhesive of the present invention has adhesive strength and conductivity equivalent to that of conventional thermosetting conductive adhesives.

2. The thickness of the adhesive layer and its variation are extremely small, so it can be used for precision processing. 3. High 1Ill
Since the content of silver powder is small, it is extremely economical.

Table 1 "Example 2" Measurement purpose: Relationship between pressure force and electrical resistance during adhesion, a5J,
Relationship between adhesive thickness and pressure
Place one roll and a support base on it, heat it at 150C, and apply adhesive to the joint surface of both.Ii'? Ill. Align the coated surfaces J, place the Uni Hindust alloy plate on the support stand, and hold it together with the support stand.
~Move from the plate to the copper plate 1° at the temperature of the support base or 120°
When the temperature reached C, inner columnar lead blocks (diameter 3 On + m) of various weights were placed on the Senjis 1 alloy plate, and left until the surface temperature reached 30 G, and then the weight was removed. except. Since the melting point of the sample adhesive was more than 70G, it remained completely solid when the load was removed.

In the case of d3 conventional adhesive, adhesive was heated for 1 hour in a constant temperature bath at 100 C with one lead plate placed on it.

Composition of the adhesive of the present invention: Silver powder (average particle size 0.5 microns) 1: Niracle powder (3.5 microns 1") 3: Wax (Shichibiru 220) 8: Rosin 2 Composition of conventional adhesive :Silver powder (average particle size 1 micron) 62:Resin (Ebicor 1 to 828) 38 (Effects of this example) 1.While the electrical resistance of conventional adhesives is not affected by pressure at all, this adhesive It can be seen that the inventive adhesive exhibits a significant change in electrical resistance.

2. Due to the thickness of the adhesive, it reacts more sensitively than conventional adhesives, but under certain pressure.
You can see that when it reaches 2, it stops changing.

Table 2

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of the bonded state. Patent rest k MausoleumegaiAζ Logic h, +w zu2° Fraud ＼
Ji-N JP-A-59-84962 (5)

Claims (1)

[Claims] A bottle made by mixing 1.00 parts by weight of a thermoplastic resin, a wax, or a mixture thereof with 5 to 150 parts by weight of one or more of silver powder, nickel powder, and graphite powder. 1-Melt conductive adhesive