JPH10309669A - Abrasive for blast working - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a grain size while holding blasting force by setting specific gravity of a glass bead, an average grain size of a composite particle and average specific gravity in a specific range. SOLUTION: Glass cullet is manufactured after melting barium-titanate glass. It is heated in a forming furnace, a coupling agent of amino silane is added to glass beads, stirred in a mixer, dried and uniformly attached on surfaces of the glass beads. Polyester resin pellets are heated and softened, mixed with the glass beads treated by the coupling agent, extruded and molded in a rod type by an extruder. Resin pellets containing the glass beads are made by cutting it by a cutter, put in a container with liquid nitrogen in it, frozen at high speed and smashed by a hammer mill. An average particle diameter of an obtained composite abrasive for blast working is 0.01-0.2 mm, average specific gravity is 1.5-3.5, and specific gravity of the glass beads is 3.5-5.0. Consequently, it is possible to favourably carry out cleaning of a precision work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite abrasive used for ultra-precision blasting.

[0002]

2. Description of the Related Art Conventionally, blasting, which is known as one of the methods for cleaning or roughening the surface of an object, involves blowing abrasive particles at a high speed onto the surface of a workpiece, and applying an impact force to the abrasive particles. In this way, the surface of the object is ground or foreign matter adhering to the surface is removed. In this blasting, the material and shape of the abrasive particles used are appropriately selected according to the material and shape of the workpiece or the purpose of the blast.

[0003] When the material of the workpiece is a metal, particularly a cast of an iron-based metal having a relatively high hardness, etc.,
Steel shots, steel grids, natural quartz sand, alumina, various artificial abrasives, or glass beads are commonly used. On the other hand, when the workpiece is made of a material having relatively low hardness such as a light metal such as copper, zinc, and aluminum, or a synthetic resin, a high-hardness abrasive such as the above steel shot requires the surface of the workpiece. Because it is deformed, ground or scratched,
Can not be used. In the case of a workpiece made of such a material having a low hardness, it is common to use a natural soft grid (corn core, walnut shell, plant seed, etc.) or a synthetic resin as an abrasive. .

[0004] As one type of blasting, there is known a method called wet blasting in which abrasive particles are dispersed in water and sprayed at a high speed. This is the case when not only the material hardness of the workpiece is low but also the shape of the processed part is fine, or when it is desired to remove only unnecessary deposits without damaging the surface of the workpiece. To
This is a particularly suitable method.

For example, in the production of semiconductor components, an IC
There is a case where a chip is fixed on a lead frame and packaged with a synthetic resin to form an IC mold, which is cleaned by blast processing. In such a case, a burr of the synthetic resin is generated at a portion where the package and the lead frame are in contact with each other, and residues of the synthetic resin adhere to the leads. Conventionally, in order to remove burrs and resin residues from these semiconductor components, wet blasting has been performed using relatively hard alumina particles or glass beads as a grinding material.

The above method has a feature that an unnecessary portion such as a resin residue and a burr at a contact portion can be removed satisfactorily without causing charging or the like, but at the same time, other normal portions are partially ground and a package is removed. Since the surface of the portion is also matted, there is a disadvantage that the product value is reduced. Even if an attempt is made to replace the abrasive with a material having a low hardness in order to eliminate such defects, in the case of wet machining, various natural soft grids cannot be used because they swell in water. In addition, since many of the synthetic resin powder particles have a specific gravity of about 1.3, they do not easily settle in still water, and if there is a water flow, they tend to rise to the upper layer of the running water. Is difficult to disperse. Therefore, it was difficult to use this as an abrasive for wet blasting.

[0007] To solve the above-mentioned difficulties of the conventional abrasive for blasting, Japanese Patent Publication No. Sho 61-5715 discloses a method.
In Japanese Patent Application Publication No. 5 (1993) -216, there has been proposed a composite abrasive in which a synthetic resin for mechanical structure such as polyacetal or polycarbonate is irregularly and firmly adhered to the outer periphery of glass beads, and has been put to practical use.

[0008] This composite abrasive combines the characteristic of the softness inherent in the synthetic resin with the characteristic of the specific gravity of the glass beads incorporated therein by combining the synthetic resin and the glass beads. Thus, the average specific gravity of the abrasive is increased to 1.5 or more. This composite abrasive can be easily dispersed uniformly in liquid without floating on the liquid surface in running water, and can selectively remove burrs without impairing the original function of precision workpieces such as lead frames. It has the feature that resin residue can be removed. In addition,
As glass beads to be embedded in synthetic resin,
A glass having a mean particle size of about 0.1 mm, which is produced from a general-purpose soda-lime glass having a specific gravity of about 2.5, which is widely used as a building sheet glass, is used favorably.

[0009]

By the way, in recent years, with further miniaturization and higher functionality of semiconductor parts, it has become necessary to reduce the pitch of related precision processed products, for example, lead frames (fine pitch). The refinement and refinement of workpieces have been further advanced. Along with this, conventional blasting composite abrasives cannot remove minute burrs or resin residues. And in order to cope with such refinement and refinement of the workpiece,
As blasting abrasives, those having a smaller particle size have been required. Therefore, in order to reduce the diameter of the composite abrasive, it is conceivable to first reduce the diameter of the glass beads used.

[0010] However, it is difficult to use the composite abrasive as a blast abrasive as it is simply by reducing the particle diameter of the composite abrasive and the particle diameter of the current glass beads contained therein. Because, in general, the kinetic energy of the abrasive particles, which becomes the impact force (blast force) during blasting,
If the flow rate of the abrasive particles is constant, it is proportional to its mass.If the composite abrasive is homogeneous, it is proportional to its volume.If the particle size of the composite abrasive is reduced by half, the impact force Is sharply reduced to 1/8.
Therefore, merely reducing the particle size of the composite abrasive and the particle size of the glass beads to be incorporated therein will cause a new difficulty of remarkably lowering the grinding ability on the workpiece. When the grinding ability is reduced, not only the processing time is prolonged and the processing efficiency is reduced, but also it is impossible to remove the target burrs and residues even if the time is extended.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned difficulties of the conventional composite abrasive, and has a blast force capable of satisfactorily cleaning a precision workpiece without impairing its original function at all. It is an object of the present invention to provide an abrasive for blasting in which the grain size is reduced as it is.

[0012]

According to the present invention, there is provided an abrasive material for blasting comprising a composite particle in which a synthetic resin is irregularly and firmly adhered to the outer periphery of a glass bead, wherein the specific gravity of the glass bead is 3.5. To 5.0, the average particle size of the composite particles is 0.01 to 0.2 mm, and the average specific gravity is 1.5.
３3.5.

In the present invention, the glass beads used preferably have a specific gravity in the range of 3.5 to 5.0.
More preferably, it is in the range of 4.0 to 4.3. If the specific gravity is smaller than 3.5, the grinding ability is reduced, and
Glass beads exceeding 0 are not preferred because they are difficult to manufacture and increase the cost.

It should be noted that there is an additive nature between the specific gravity of the glass and the chemical composition, and the specific gravity can be obtained by a general calculation from the weight fraction of the oxide component constituting the glass. By including a large amount of an oxide of an element having a large atomic weight, such as barium, in a glass component, glass beads having the above specific gravity range can be easily produced.

Examples of currently commercially available glass having a high specific gravity include lead glass, fluoride glass, barium glass and the like. However, the present invention is not limited to any glass composition as long as it can be set within the above specific gravity range. May be used.
It is preferable to determine the composition in consideration of the cost and the effect on the environment.

The glass beads according to the present invention preferably have a particle size of 0.1 mm or less, more preferably 0.01 to 0.05 mm. Particle size 0.1m
If it exceeds m, the amount of synthetic resin adhering to the outer periphery is reduced, and the buffering force on the workpiece is weakened. As a result, the workpiece may be damaged, which is not preferable. In addition,
In the present invention, there is no particular lower limit on the particle size of the glass beads that can be used, and ultrafine glass beads having a particle size smaller than 0.01 mm can be used. The ultra-fine glass beads can be satisfactorily prepared by combining a plurality of them or combining them with glass beads larger than 0.01 mm, and setting the average particle diameter and the average specific gravity of the composite particles within the range of the present invention. Can be used.

The glass beads having such a particle diameter may be obtained by using a glass material having a smaller particle diameter obtained by pulverizing the glass, or by producing a conventional glass bead having an average particle diameter of about 0.1 mm, followed by sieving. It can be easily obtained by selecting beads having an appropriate particle size according to the air classification or air classification.

In the present invention, any synthetic resin that can be used to coat the glass beads, as long as it has no water absorption and can set the average specific gravity in the range of the present invention in combination with the above glass beads, can be used. Any material such as a thermoplastic or thermosetting resin may be used. For example, a general-purpose synthetic resin such as a urea resin (specific gravity of about 1.5), a melamine resin (specific gravity of about 1.5), an acrylic resin (specific gravity of about 1.2), or a polyester resin (specific gravity of about 1.2) is used. Synthetic resin has a relatively low specific gravity and hardness and can be more mildly contacted with a workpiece during blasting, so that it can be used particularly preferably.

Resins generally called synthetic resins for mechanical structures, such as polycarbonate resins (specific gravity 1.3), polyacetal resins (specific gravity 1.4), and epoxy resins (specific gravity 1.2), are also commonly used. Although it has a slightly higher hardness than resin, it can be used similarly.

In producing the composite abrasive of the present invention, the specific gravity and particle size of the glass beads used, the specific gravity of the synthetic resin, and the weight ratio and volume ratio of the glass beads and the synthetic resin are determined by the obtained composite abrasive particles. Has an average specific gravity of 1.5
It is preferable that the particle size is appropriately selected so that the average particle size becomes 0.01 to 0.2 mm. If the average specific gravity of the composite abrasive particles is less than 1.5, the particles will float in running water, making it difficult to uniformly disperse them, and therefore are not preferable for wet blasting. If it exceeds 3.5, the impact force is so strong that the surface of the workpiece is unnecessarily ground, deformed or damaged, which is not preferable.

The composite abrasive for blasting of the present invention can be manufactured basically in the same manner as the manufacturing method described in JP-B-61-57155. That is, first, a coupling agent is attached to the periphery of the glass beads, and then the glass beads are mixed well with the synthetic resin, and then cured and pelletized by a method suitable for the properties of the synthetic resin. After rapid freezing, the mixture is crushed until the particle size becomes a predetermined size, thereby obtaining composite particles in which the synthetic resin is irregularly and firmly adhered to the outer periphery of each glass bead.

The composite abrasive for blasting according to the present invention is prepared by adhering a coupling agent to the outer periphery of glass beads during the production thereof, as in the case of the composite abrasive described in JP-B-61-57155. The glass beads and the synthetic resin can be firmly bonded during the mixing step. Therefore, in the composite abrasive of the present invention, the glass beads and the synthetic resin portion do not peel off during the blasting, and therefore, there is no possibility that the original function of the workpiece is impaired.

In the present invention, since the average specific gravity of the composite particles is increased to 1.5 to 3.5 by incorporating glass beads having a large specific gravity in the synthetic resin portion, the average particle size of the composite particles is 0.1 to 3.5. Despite being as small as 2 mm or less, more precise blasting can be performed without reducing the impact force on the workpiece. In addition, when dispersed in running water, the abrasive can be uniformly mixed without floating on the liquid surface, and thus is particularly suitable as an abrasive for wet blasting. Since soft synthetic resin with small hardness contacts the workpiece more mildly during blasting,
Burrs and resin residues can be effectively removed without impairing the original function of the workpiece. As described above, the abrasive for blasting of the present invention can be used for removing, for example, a finer synthetic resin burr between the leads and between the leads and between the leads, which is more precise, and for cleaning, etc. It is suitable for the blasting of precision workpieces.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to embodiments.

Example 1 After melting barium-titanate glass (specific gravity 4.2),
Place in a water tank, granulate and dry, then ball mill for about 10
The glass cullet having an average particle diameter of 0.05 mm was produced by further pulverizing and classifying for an hour. This was heated in a molding furnace to obtain glass beads having an average particle size of 0.05 mm. Thereafter, 0.1 wt% of an aminosilane coupling agent was added to the glass beads, and the mixture was stirred for about 30 minutes in a mixer, dried, and uniformly adhered to the surface of the glass beads.

Next, 0.6 kg of commercially available polyester resin pellets (specific gravity: about 1.2) is heated and softened, mixed well with 0.4 kg of the above glass beads treated with a coupling agent, and extruded into a rod shape using an extruder. Molded. This was cut with a cutter to form a resin pellet containing glass beads. The pellet was placed in a container containing liquid nitrogen, rapidly frozen at a temperature of -50 to -195 ° C, taken out, and ground with a hammer mill. Thus, the composite particles were obtained as a pulverized product. The obtained composite abrasive for blasting of the present invention has an average particle size of 0.1 mm and an average specific gravity of 2.4.
Met.

Deburring of the lead frame was performed by wet blasting using this abrasive, but fine burrs between the leads could be completely removed without damaging the main body at all.

Example 2 A composite abrasive was produced in the same manner as in Example 1 except that a urea resin (specific gravity 1.5) was used as a synthetic resin. The average particle size of the obtained composite abrasive of the present invention was 0.1 mm, and the average specific gravity was 2.6.

The lead frame was deburred in the same manner as in Example 1 by wet blasting using this abrasive. Fine burrs between the leads could be completely removed.

Comparative Example Soda-lime glass (specific gravity 2.5) as glass beads
Except that the average particle size was 0.1
mm composite abrasive was produced. The average specific gravity of the obtained composite abrasive was 1.7.

The lead frame was deburred in the same manner as in Example 1 by wet blasting using this abrasive. Although the frame body was not damaged, it took twice as long to completely remove the fine burrs between the leads as compared with the composite abrasive of Example 1.

[0032]

As described above, according to the composite abrasive for blasting of the present invention, it is possible to precisely clean a workpiece such as an electronic component corresponding to fine pitch.
It can be carried out satisfactorily without reducing the efficiency and without impairing the original function of the workpiece at all.

[0033]

Claims (3)

[Claims] 1. A blasting abrasive comprising composite particles in which a synthetic resin is irregularly and firmly adhered to the outer periphery of a glass bead, wherein the specific gravity of the glass bead is 3.5 to 5.0, An abrasive for blasting, wherein the composite particles have an average particle size of 0.01 to 0.2 mm and an average specific gravity of 1.5 to 3.5. 2. The abrasive according to claim 1, wherein said glass beads contain barium. 3. The composite particle according to claim 1, wherein the composite particle is for wet blasting.
Abrasive material for blasting as described.