JPS59117223A - Method for removing burrs from semiconductor plastic packaging resin - Google Patents

Abstract

PURPOSE:To dissolve the problem of generation of powdery dust, etc., to be generated when a flash is removal according to high speed jet of a powdery matter by a method wherein a laser beam is irradiated to the flash. CONSTITUTION:The unnecessary flashes 30, 31 of a semiconductor IC package 1 are molten to be evaporated and removed by irradiating to package leads 2 a laser beam 5 adjusting output, the irradiating diameter, the irradiating hours thereof as to make the temperature to satisfy the condition that the resin melting temperature is smaller than the lead frame material melting temperature in the condition that the package is sheltered by a mask 4. As the lead frame material, the metal frame of 42 alloy material, etc., are used mainly, while it is necessary to irradiate the laser beam within the extent not to apply deformation and abnormality to the lead frame material thereof. As the laser beam 5, any of YAG laser, CO2 laser, etc., having the wavelength in the extent not to transmit through the resin is favorable. Moreover because the resin flashes are generated on both sides of the package 1, it is necessary to irradiated again by turning the beam from side of side when the beam is irradiated from one direction, while it may be also favorable to irradiate at the same time from both the sides.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing resin particles around a pan cage lead frame, which are generated during molding of semiconductor and IC (integrated circuit) plastic packages, using laser light.

There are various types of semiconductor packages, such as ceramic types, cerdip types, and plastic types.Plastic types generally involve mounting the chip on a lead frame, then wire bonding, then putting it in a mold and using epoxy resin, etc. A method of transfer molding using resin is used.

At this time, resin burrs occur on the lead frame portion around the outer periphery of the package. The cracks that occur during resin molding are an unavoidable phenomenon due to mold processing accuracy. Conventionally, this pulp has been removed by crushing and knocking it off with a high-speed jet of walnut powder, but since the charged walnut powder adheres to the package, it becomes necessary to remove it. This removal work requires time and effort. In addition, it is difficult to handle the powder because it requires careful attention to dust-proofing and explosion-proofing even on the entire surface of the room, where the powder must be sufficiently dry and stored in advance. In addition, the mask for protecting the package was easily worn out by high-speed spraying, so it could not be used for a long period of time.

The object of the present invention is to eliminate the drawbacks of removing unnecessary resin debris from a package by high-speed jetting of powder, and to provide a method for removing debris using a novel laser light irradiation method.

The present invention will be explained below based on drawings showing embodiments.

FIG. 1A is a plan view illustrating the occurrence of resin burrs, in which unnecessary resin burrs occur on the outer package lead 2 of a resin package 1 for a semiconductor or IC. Note that internal devices such as elements and wire bonding are omitted from the package 1.

FIG. 1B is a sectional view taken along the line x-x' in FIG. 1A,
Resin burrs 30 and 31 occur on both sides of the package 1.

Next, the present invention will be explained in detail based on FIGS. 2A and 2B.

With the mask 4 closed on the semiconductor and IC pancase 1, the package lead 21τ is irradiated with the laser light 5 with the output and irradiation diameter adjusted for 1 hour so that the melting temperature of the resin is equal to the melting temperature of the lead frame material, as shown in Figure 2B. By doing so, unnecessary particles 30 and 31 of the package are melted and evaporated and removed.

Note that the package lead 2 is omitted in FIG. 2A.

A metal frame such as 4270I material is mainly used as the lead frame material, and in the above process, it is necessary to irradiate the laser light within a range that does not cause deformation or abnormality to the lead frame material. Through the above process, only unnecessary resin burrs are selectively removed.

The mask 4 may be a metal mask similar to that conventionally used for deburring with walnut powder.

Even if there is a large resin burr, it can be easily peeled off due to the difference in shrinkage rate of the material due to instantaneous heating by the laser light, so it can be removed by blowing a little air after irradiating the laser light.

The influence of the heat on the package lead 2 can be ignored since it is carried out at a melting temperature lower than that of the lead, and the influence on the internal elements of the package can also be ignored because instantaneous laser irradiation is sufficient.

Since the laser light can be controlled electrically, the mask 4 may be omitted and the laser beam may be removed without programming by scanning only the outer periphery of the package as shown by reference numeral 6 in FIG. 3 in advance.

The laser light 5 is YAG (Yttrium Al
Any material may be used as long as it has a wavelength range that does not pass through the resin, such as umi num Garnet) laser, CO, and laser.

Note that resin burrs occur on both sides of the package 10, so when laser light is irradiated in one direction, it is necessary to reverse the laser light and re-irradiate it.
Simultaneous irradiation may be performed from both sides.

According to the present invention, unnecessary pars around the package lead frame can be removed without affecting the semiconductor, the main body of the IC package, and the lead frame, and only the pars can be selectively removed in a short time using laser light, and in a reliable manner. It is easy to handle because there are almost no dust problems like when using walnut powder, and there is no chance of walnut powder adhering to the package or lead frame, so these packages or lead frames may get dirty. It has an excellent effect of not causing any problems.

[Brief explanation of drawings]

Figure 1A is a plan view illustrating the state of occurrence of resin flakes in the present invention, Figure 1B is a sectional view taken along the line xx' in Figure 1A, and Figure 2A is a plane view illustrating the state in which the package is protected by a mask. FIG. 2B is a sectional view taken along line Y-Y' in FIG. 2A, and FIG. 3 is a plan view illustrating the scanning path of laser light. 1...Package, 2...Package lead, 30
゜31...Resin burr. Figure 1A Figure 2A Figure 28 Figure 3 No. 1

Claims (1)

[Claims] Unnecessary cracks around the lead frame that occur during molding of semiconductor plastic packages. A burr removal method characterized by removing burrs by irradiating them with laser light.