JPH0360631B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an abrasive material made of synthetic resin, and particularly to an abrasive material that has the ability to generate sharp edges (hereinafter referred to as self-sharpening ability) during blast processing.

[Technical background of the invention]

In order to perform surface treatment on soft metals and remove burrs from electronic device parts, a method is used in which the abrasive material is accelerated with compressed air and is jetted by colliding with the soft metal or electronic device parts being processed. . Conventionally, walnut shell powder and apricot shell powder have been used as such abrasives.

[Problems with background technology]

However, vegetable-based walnut shell powder and apricot shell powder have high elasticity and stickiness when dry, so when these are used as abrasives to blast the workpiece, the edges of the abrasives The drawback was that the polishing force was reduced in a short period of time due to rounded edges. Therefore, when such an abrasive is applied to, for example, removing resin burrs from a semiconductor molded product, the resin burrs present on the lead frame of the molded product and between narrowly spaced leads cannot be sufficiently removed.

[Purpose of the invention]

The present invention aims to provide an abrasive material that can exhibit good abrasive power over a long period of time when blasting a workpiece and is suitable for machining fine parts.

[Summary of the invention]

The abrasive material according to the present invention is characterized in that it is composed of a mixture of flat synthetic resin granules, acicular synthetic resin granules, and granular synthetic resin granules each having a large number of edges.

Each of the particles has a large number of edges, and
Since the granules are to be cracked and new edges are formed due to collision with the workpiece during the jetting process using compressed air, each of the granules may be formed from a synthetic resin with moderately limited hardness and ductility. desirable. Examples of such synthetic resins include thermosetting resins such as epoxy resins, urea resins, and polyester resins, as well as relatively hard thermoplastic resins such as acrylic resins.

The mixture is formed by mixing appropriate amounts of each of the synthetic resin particles.

The size of the synthetic resin granules can be freely selected depending on the use of the abrasive, but for example, when used for removing resin burrs from molded products, the average diameter (the sum of the maximum diameter and minimum diameter of one granule) 1/2) with a peak within the range of 0.05 to 2.0 mm.

In order to produce the abrasive material of the present invention described above, for example, a lump of synthetic resin material is processed in various types of crushers, such as a masticator, a rotary crusher, a roll crusher, a disk crusher,
Corn crusher, hammer mill, edge runner,
A method of pulverizing with a centrifugal mill, ball mill, tube mill, etc. can be adopted.

Since the abrasive material of the present invention is composed of a mixture of flat synthetic resin granules, acicular synthetic resin granules, and granular synthetic resin granules each having a large number of edges, the abrasive material is accelerated with compressed air and When spray processing is performed by colliding with an object, the workpiece can be effectively ground or deburred by local collisions caused by the many edges of each synthetic resin granule constituting the mixture. Furthermore, the flat synthetic resin granules and acicular synthetic resin granules that make up the mixture have a high so-called self-sharpening effect that breaks during the collision and forms new edges, so they provide excellent protection even during long-term use. Grinding or deburring performance of the workpiece can be maintained.

Furthermore, if an abrasive material is formed by retaining a surfactant in the synthetic resin granules, it is possible to prevent the generation of electrical charge on the workpiece, especially when the workpiece is subjected to dry blasting using this abrasive material. It is possible to easily clean the workpiece after the blast treatment.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The abrasive material of this embodiment is an abrasive material made of flat synthetic resin particles such as unsaturated polyester resin, epoxy resin, urea resin, acrylic resin, etc., having a large number of edges 1 as shown in FIG. 2 and a granular abrasive material 2' made of a synthetic resin of the same quality as the abrasive material 2 having a large number of edges 1 as shown in FIG. It is a mixture of acicular abrasive material 2''.
The average diameter of each of the abrasive materials 2, 2', 2'' is within the range of 0.05 to 0.2 mm with a peak of around 0.3 mm. The percentages range from 0.1% to less than 100%, respectively.

In order to obtain the abrasive materials 2, 2', 2'', the synthetic resin material in the form of a block is coarsely pulverized using a crusher, hammer, etc., and then a variety of pulverizers such as a masticator, a rotary pulverizer, a disc pulverizer, a cone pulverizer are used. The abrasives 2, 2', 2 obtained in this manner are obtained by pulverizing them using a machine, hammer mill, Edge Runner centrifugal mill, tube mill, ball mill, roll mill, impact pulverizer, etc. '', but if the mixing ratio is different from the desired value, add the respective abrasives 2, 2',
2'' is made individually and mixed to a desired value. That is, the flat abrasive material 2 can be obtained by crushing a plate-shaped synthetic resin material with a thickness of 1.0 mm or less, for example. Further, the granular abrasive material 2' can be obtained, for example, by crushing a plate-like or rod-like synthetic resin material with a thickness of several tens of millimeters or less, and then passing it through an air sieve.Furthermore, the acicular abrasive material 2''
is obtained by pinching and pressing a thread-like synthetic resin material with a diameter of around 0.1 mm between a pair of rollers and then passing it through a wind sieve.

Next, the removal of resin burrs from the semiconductor molded product shown in FIG. 4 using the abrasive material will be explained using the wet-type plast apparatus shown in FIG. 5.

After the lead flail on which the semiconductor element is mounted is housed in a molding mold in advance, epoxy resin is injected into the mold to form a semiconductor element (not shown) on the lead frame 3 as shown in FIG. A semiconductor molded product 5 sealed with a resin layer 4 was molded.
In this molded product 5, resin burrs 6 were generated on the lead frame 3 near the resin layer 4 and between the leads of the lead frame 3 during molding.

Next, the abrasive materials 2..., 2'..., 2''... and water 9 are placed in a hopper 8 installed in the pressurizing chamber 7 shown in FIG.
were housed in a ratio of 1:3. Next, the first pump 10 is operated to suck in the abrasive materials 2... together with the water 9, and the abrasive materials 2..., 2'..., 2'' are forcibly fed to the bottom of the hopper 8 and stirred. A slurry was prepared by uniformly dispersing...

Next, the second pump 11 is operated to suck up the slurry and introduce it into the gun 12, and the slurry is dispersed and accelerated by compressed air from the air introduction pipe 13 to become water,
A three-phase high-speed jet stream 14 of abrasive material and air was injected toward the aforementioned semiconductor molded product (not shown) transported into the processing chamber 7. When the jet stream is injected onto the molded product in this way, as shown in FIG. collides with the resin burr 6. The resin burr 6 is made of thermosetting epoxy resin and is brittle and easily broken.
A crack 15 is generated in the resin burr 6 due to the concentrated (local) impact force by the edge 1 of 2'' and the vibration accompanying the impact force.Moreover, water penetrates into the crack 15 generated in the resin burr 6. The resin burr 6 enters the interface between the lead frame 3 and the resin burr 6 and acts to lift the resin burr 6 relative to the lead frame 3.
Further, abrasive materials 2, 2', having a large number of edges 1...
2'' collides with the crack 15 of the resin burr 6 many times, and together with the floating action of the resin burr 6 by the infiltrated water, the resin burr 6 is completely removed.

Further, the abrasive materials 2, 2', 2'' have a large number of edges 1...
Due to the collision with the semiconductor molded product 5 , the rounded edges of the abrasives 2, 2', 2'' themselves break and fall off, for example, along the dashed line in FIG. New edges 1' are formed as shown in b.As a result, the ability to remove resin burrs 6 from the semiconductor molded product 5 can be maintained even during long-term use.Furthermore, the polishing material 2 of the present invention,
2' and 2'', for example, when a semiconductor molded product 5 is jet-processed, the flat abrasive material 2 and the needle-like abrasive material 2" are used to fill the gap between the leads of the lead frame 3 of the semiconductor molded product 5 and The probability of colliding with the resin burrs 6 that are generated in narrow, minute areas near the boundary between the resin layer 4 and the lead frame 3 is higher than that of the granular abrasive 2', and as a result, the resin that is generated in these areas The burrs 6 are mainly removed by the abrasives 2 and 2''. Furthermore, the granular abrasives 2' mainly contribute to the removal of resin burrs generated on the lead frame 3. Therefore, the molding The resin burrs 6 on the molded product 5 can be evenly and effectively removed, and the resin burrs 6 attached to minute parts of the molded product 5 (for example, between the leads of the lead frame 3) can also be removed by the edges 1 of the abrasive 2. Can be completely removed without leaving any residue.

By the way, the ratio of flat abrasive material 2 is 30 to 10
%, the proportion of granular abrasive material 2' is 50 to 80%, the proportion of acicular abrasive material 2'' is 10 to 20%, and the average particle diameter which is the arithmetic average of the maximum diameter and minimum diameter of each is 0.2 ~
1.6mm (However, if the object to be deburred is a semiconductor device, determine the average particle size so that it is less than the gap between the leads.) The tip angle of the edge part is 180mm.
FIG. 7 shows the deburring properties of the resin portion of a semiconductor device using an abrasive with a radius of 0.2 mm or less and an edge tip radius of 0.2 mm or less.
The test conditions at this time were to deburr a semiconductor device using a wet blasting machine for 24 hours continuously, then deburr 10,000 devices, and arbitrarily sample 1,000 of these 10,000 workpieces. The percentage of completely deburred workpieces among the processed workpieces is expressed as 100% deburring property. As can be seen from this figure, the abrasive material of this example has almost no deburring properties.
100%, whereas the average particle size of the spherical or cylindrical abrasives shown as a comparative example is
When using an abrasive in the range of 0.2 to 1.6 mm, the deburrability is approximately 80%. Therefore, it is clear that the abrasive material of this example has extremely excellent deburring properties.

In the example, deburring is performed using a mixture of abrasives 2, 2', and 2'', but these may be used alone, or a mixture of flat abrasive 2 and granular abrasives may be used. 2', a combination of a flat abrasive material 2 and a needle-like abrasive material 2'', and a combination of a granular abrasive material 2' and a needle-like abrasive material 2''. Deburring can be carried out in the same manner.In order to adjust the hardness of the abrasives 2, 2', 2'', it is optional to include a component that lowers the hardness.

Furthermore, the injection processing using the abrasive of the present invention is not limited to the purpose of removing resin burrs from semiconductor molded products as in the above embodiments, but can also be used for removing resin burrs from general molded products, surface treatment of soft metals, etc. can be similarly applied. However, when using a mixture of abrasives 2, 2', and 2'' for plastic processing of semiconductor molded products, it is recommended to use one in which the proportion of granular abrasives 2' is greater than that of other abrasives 2, 2''. preferable.
Further, in order to remove resin burrs from the diode, it is preferable to use an abrasive material in which the proportion of the needle-like abrasive material 2'' and the flat abrasive material 2 is greater than that of the granular abrasive material 2'.

〔Effect of the invention〕

As described in detail above, according to the present invention, when injection processing is performed on workpieces such as semiconductor molded products or other molded products or soft metals in which resin burrs are generated during molding, the workpieces can be sprayed even after long-term use. It is possible to provide an abrasive material having good abrasive power that can remove resin burrs or maintain grindability.

[Brief explanation of drawings]

FIG. 1a is a perspective view of an abrasive material according to an embodiment of the present invention, FIG. 1b is a perspective view of an abrasive material in which new edges have been formed by the self-sharpening action, and FIGS.
The figure is a perspective view of an abrasive used together with the abrasive in Fig. 1, Fig. 4 is a plan view of a semiconductor molded product, and Fig. 5 is a wet blasting device used to remove resin burrs from a semiconductor molded product using an abrasive. FIG. 6 is a cross-sectional view for explaining resin burr removal using an abrasive material, and FIG. 7 is a graph showing burr removal properties of an example of the present invention and a comparative example. 1, 1'...Edge, 2, 2', 2''...Abrasive material,
3...Lead frame, 5 ...Semiconductor molded product, 6...Resin burr, 7...Processing chamber, 8...Hopper, 9...Water, 10, 11...Pump, 12...
...Gun, 15...Crack.

Claims (1)

[Claims] 1. An abrasive material comprising a mixture of flat synthetic resin granules, acicular synthetic resin granules, and granular synthetic resin granules, each of which has a large number of edges.