JPH0931687A - Method for polishing lead frame material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for polishing a lead frame material capable of efficiently removing the ruggedness and burrs on a lead surface without inducing deformation in the lead itself. SOLUTION: An infection gun 1 has a nozzle 1a. Compressed air and a fluid mixture M composed of water and abrasive grains are mixed in this injection gun 1. This fluid mixture is blown to the lead frame material moving at a prescribed speed from the nozzle 1a formed to a slit form. Such blowing is executed toward both front and rear surfaces of the lead frame material from an approximately perpendicular direction at least once each for the respective surfaces. An extremely good result is obtd. if alumina particles or a material mixture composed of the alumina particles and glass beads is used as the abrasive grains under prescribed conditions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment method during a manufacturing process of a lead frame used for electronic parts such as IC and LSI, and particularly to a treatment suitable for removing irregularities and burrs on the surface of a lead frame material. Regarding the method.

[0002]

2. Description of the Related Art Generally, a method of manufacturing a lead frame is
First, a lead frame material is obtained by punching a plate material (hoop material) of a copper alloy or an iron alloy obtained by rolling processing with a press machine. The lead frame material is in a state in which lead portions and the like are formed for each lead frame, but is not completely cut in lead frame units. Next, such a lead frame material is subjected to a pretreatment, then a plating treatment is performed, and finally, the lead frame material is completely cut into lead frame units to complete the process.

In the above steps, the pretreatment step is an extremely important step. That is, the lead frame material usually has a surface area of 0.4 to 0.8 μm generated by rolling.
In addition to the concavo-convex part, the length generated in the punching process is 5-40
There are various burrs of μm. When such a surface is directly plated, swelling or peeling occurs, and it is impossible to obtain a uniform plating thickness. Therefore, a pretreatment process is provided before the plating process to remove surface irregularities and various burrs.

Several methods have been proposed and adopted as such a pretreatment method, but as a very general method, there is a method incorporating a chemical polishing method. In this method, after dipping the lead frame material in a degreasing liquid to degrease it,
Washing with water, immersion in a chemical polishing liquid, and washing with water are carried out in this order. However, this method makes it difficult to control the chemical polishing bath.
Moreover, since the liquid composition is not generally clarified, it is necessary to entrust the waste liquid treatment to a specialist, which is a major obstacle to reducing the manufacturing cost of the lead frame. Moreover, removal of surface irregularities and burrs is not always sufficient.

As a method for improving the above drawbacks, there is a pretreatment method which incorporates an electrolytic polishing method. In this electrolytic polishing method, the electric current value and the polarity can be arbitrarily selected, and the electrolytic polishing solution can be self-made, so that the waste solution can be treated in-house, which is advantageous over the chemical polishing method. However, this method requires an expensive power supply device, tends to cause unevenness in the finish for each lot, and is not always sufficient for removing one-sided burrs and needle burrs generated in the straight portion of the lead. .

A dry blasting method is a method different from the above two examples. In this method, for example, aluminum powder or glass powder is blown onto the lead frame material together with high pressure air. However, in this method, post-treatment is required because those particles adhere to the surface of the lead frame material after the treatment, and a degreasing step is indispensable before the blast treatment, so that the manufacturing cost is not necessarily reduced. However, there is a possibility that the lead frame material may be deformed, which is not sufficient.

Another method is to use a jet pump and spray high-pressure water of 50 to 70 atm. However, this method also requires a degreasing step and does not always contribute to cost reduction. Moreover, sufficient impact force cannot be obtained with water alone, and removal of burrs is not sufficient. In particular, when trying to remove the one-sided burr or the needle burr generated in the straight portion of the lead, the water pressure is unavoidably increased, which may deform the lead frame material.

[0008]

By the way, in recent lead frames, further increase in the number of pins is required, and the distance between the tips of the leads is becoming extremely narrow, for example, 100 μm. Therefore, in each of the above-mentioned methods, when trying to remove the one-sided burr or the needle burr generated in the straight part of the lead, the surface of the lead is inevitably excessively polished, resulting in the lead shape being disturbed. .

In order to improve this point, a method is proposed in which a mixed fluid of a degreasing liquid and high-pressure air is sprayed onto the front and back surfaces of the lead frame material at least once at a substantially vertical direction. Has been done. However, although this method is effective in removing burrs called straight burrs and needle burrs generated in the straight portion of the lead, it is not sufficient for removing the irregularities on the lead surface.

The present invention has been made to solve the above problems, and its purpose is to:
It is an object of the present invention to provide a method for polishing a lead frame material, which enables efficient removal of irregularities and burrs on the lead surface without causing deformation of the lead itself.

[0011]

In order to achieve the above object, the method for polishing a lead frame material according to the present invention comprises:
Prepare a mixed fluid of abrasive grains, water and air, and the mixed fluid,
The lead frame material is sprayed onto both the front and back surfaces at least once in a direction substantially perpendicular to the front and back surfaces. Further, as the abrasive grains, preferably, only alumina particles are used, and the particle concentration in the slurry containing the alumina particles is set to 80 to 800 g / liter. Further, as the abrasive grains, preferably, mixed particles of alumina particles and glass beads are used, and the slurry containing the mixed particles has an alumina particle concentration of 5 to 600 g / liter and a glass bead concentration of 70 to 700 g / l.
Let it be liters.

Further, when the abrasive grains are made of only alumina particles, it is preferable that the upper limit of the average particle diameter of the alumina particles is 1/3 of the lead interval and the lower limit thereof is 8 μm. Furthermore, when the abrasive grains are mixed grains of alumina particles and glass beads, the upper limit of the average grain size of the abrasive grains is preferably 1/3 of the lead interval, and the lower limit of the alumina particles is 8 μm. And the lower limit of the glass beads is 10μ
be m. Furthermore, the lead spacing is 100μ
When it is around m, it is preferable that the alumina particles have an average particle diameter of 8 to 20 μm and the glass beads have an average particle diameter of 10 to 20 μm.

[0013]

According to the present invention, a plate material (hoop material) of a copper alloy or an iron alloy obtained by rolling is punched by a press machine to produce a lead frame material, and a mixed fluid of abrasive grains, water and air is added to the lead frame material. The lead frame material is sprayed onto both the front and back surfaces at least once in a direction substantially perpendicular to the front and back surfaces. As a result, the lead itself is not deformed, and the irregularities and burrs generated in the previous step can be efficiently removed. In that case, the abrasive grains are alumina particles alone or a mixture of alumina particles and glass beads, and the concentration of the abrasive grains in the slurry containing the abrasive grains is 80 to 800 g / liter in the former case.
In the latter case, the alumina particles are 5 to 600 g / liter, the glass beads are 70 to 700 g / liter, and the average particle diameter of the abrasive grains is 1/3 of the lead interval and the lower limit of the alumina particles. Is 8 μm, and in the case of glass beads, 10 μm, a very suitable effect can be obtained.

[0014]

Embodiments of the present invention will be described with reference to FIGS. First, a part of the equipment and the lead frame material used for carrying out the present invention will be described.
FIG. 1 schematically shows a part of the equipment. In FIG. 1, the injection gun 1 is supplied with compressed air A from one side and is supplied with a mixed fluid M of water and abrasive grains from the other side. The spray gun 1 sprays the mixed fluid M mixed and pressurized in the mixing chamber from the slit-shaped nozzle 1a onto a lead frame material (not shown).

The lead frame material is C7025.
Made of (copper alloy), thickness 150 μm, width 50 mm,
A thin plate having a length of 200 mm was used in which five patterns each having a lead interval of 100 μm, a lead width of 100 μm, and 208 pins (leads) were formed by punching. The spraying process was performed while changing the relative position between the injection gun 1 and the lead frame material at a predetermined speed, and was performed on both the front and back surfaces of the lead frame material the same number of times and from the direction perpendicular to each surface. Another injection gun 2 is shown in FIG. The nozzle 2a of this injection gun 2 has a circular shape,
When using such an injection gun 2, almost the same result as when using the injection gun 1 of FIG. 1 was obtained.

Next, consideration of selection of abrasive grains and results of using the same will be described. In the present invention, it is preferable to use alumina particles as the abrasive grains. The reason is that since normal alumina particles have a fracture surface, the surface of the lead frame material is cut by this fracture surface,
This is because the unevenness can be effectively removed. However, depending on the material of the lead frame material and other processing conditions, the cutting effect may be too strong with only the alumina particles. In that case, if the processing conditions are adjusted so as to weaken the cutting effect, the deburring effect will drastically decrease, but if the spherical glass beads are mixed without changing the processing conditions, the cutting effect will weaken and optimization can be achieved experimentally. Was done.

The concentration of the abrasive grains in the slurry containing the abrasive grains is 80 to 800 g / liter when the abrasive grains are only alumina particles, and when the abrasive grains are a mixture of alumina particles and glass beads, Experiments have shown that it is preferable to use alumina particles of 5 to 600 g / liter and glass beads of 70 to 700 g / liter. If the amount of abrasive grains exceeds the above range, abrasion of the injection gun and piping becomes a problem, and the cutting effect is rather reduced. It was also found that if the amount is less than this range, a sufficient cutting effect cannot be obtained.

The average grain size of the abrasive grains depends on the lead spacing. As a matter of course, if the grain size is larger than the lead interval, the burr existing on the side surface between the leads cannot be removed, and the impact on the leads becomes too strong, and the leads are deformed. Usually, it is desired that the particle size is smaller than 1/3 of the lead interval. The reason is that if the particle size is smaller than the lead interval and is larger than ⅓, a bridge is formed between the particles, and the same adverse effect as when the particle size is larger than the lead interval occurs. On the other hand, if it is too small, the cutting effect and the burr removal effect are small, and it has been found that it is preferable to set the lower limit of the average particle size of alumina particles to 8 μm and 10 μm for glass beads.

Further, what should be noted in carrying out the present invention is the setting of various conditions for spraying the mixed fluid onto the lead frame material from the nozzle of the injection gun. These conditions include the distance between the lead frame material and the nozzle of the spray gun, the discharge amount of the mixed fluid discharged from the nozzle, the pressure of the abrasive grain slurry and the air pressure for forming the mixed fluid, and the spraying. The amount of mixed fluid and the processing speed of the lead frame material are included. Since these conditions are closely related to each other, it is meaningless to specify them on a condition-by-condition basis, and it is necessary to carefully consider and set the optimum conditions before mass production.

Next, the test results obtained by studying under various conditions will be individually described for 13 examples as examples of the present invention and 5 examples as comparative examples. It should be noted that FIGS. 3 to 13 will be referred to in describing them. (A) of each figure shows the removal state of burrs, and (b) shows the smoothness of the treated surface and the pattern part as the center. The deformation state of the lead frame material is shown. The symbols commonly used in (a) of these figures have the following meanings. ○: Indicates that the burr was removed. X: Indicates that the burr was not removed. Δ: Indicates that some burr remained. The symbols commonly used in (b) of each figure have the following meanings. ◯: Indicates that a good surface was obtained. X: Indicates that a good surface was not obtained. Δ: It is an intermediate value between them and shows that it is almost good.

Example 1 Alumina particles having an average particle size of 8.0 μm were used as abrasive grains,
The concentration of alumina particles in the slurry was 530 g / liter,
The projection distance, that is, the distance between the nozzle 1a of the injection gun 1 and the lead frame material was set to 20 mm. Further, the discharge pressure of the pump for discharging the abrasive slurry was adjusted to 1.25 kg / cm ² , and the input air pressure was 0.7 to 3.0 kg / cm ² .
Further, the injection gun 1 was fixed and the lead frame material was moved, but the moving speed was 3 m / min. The amount of air blown in was 1500 liters / minute · nozzle, and the shape of the lead frame material surface formed by the mixture of air and slurry blown from the nozzle 1a of the injection gun 1 was 90 mm.
It was a line of 1.6 mm.

The result of this operation is as shown in FIG. 3, and the obtained color tone is satin (state like the surface of 20th century pears),
It was matte. As can be seen from this figure, when the input air pressure is low, the burr can be removed by increasing the number of times of spraying (the number of times of projection). In addition, the input air pressure is 3 kg / c
If it is m ² or more, the burr can be removed regardless of the number of projections, but the surface is rather rough, and the deformation in the pattern portion appears largely as the number of projections increases. Further, even if the input air pressure was low, the surface became rough and the pattern portion was deformed when the number of projections increased.

Example 2 The same conditions as in Example 1 were used except that alumina particles having an average particle size of 11.5 μm were used as abrasive grains. The results are as shown in FIG. 4, and the obtained color tone was satin and matte. Basically, the same results as in Example 1 were obtained, but the degree of cutting on the surface was high, and the scratches during rolling were less visible than in Example 1.

Example 3 The same conditions as in Example 1 were used except that alumina particles having an average particle size of 14.0 μm were used as abrasive grains. The results are shown in FIG. 5, and the color tone obtained was satin and matte. It can be seen that, as compared with Examples 1 and 2, the range in which a good surface is obtained is narrowed, and the degree of freedom in setting conditions is being lost.

Example 4 All were carried out under the same conditions as in Example 1 except that alumina particles having an average particle size of 20.0 μm were used as abrasive grains. The result is as shown in FIG. 6, and the obtained color tone was satin and matte, but the satin was strong. As compared with Examples 1 to 3, the range where a good surface can be obtained becomes extremely narrow, and it is found that it is dangerous to use alumina particles having a larger particle size than this. Even in this case, if the projection distance is increased, it is possible to obtain the results of the first and second embodiments, but in any case, it is understood that the degree of freedom in setting the conditions is being lost.

Example 5 Alumina particles having an average particle size of 11.5 μm and glass beads having an average particle size of 20 μm were used as abrasives, the concentration of alumina particles in the chiller was 150 g / liter, and the concentration of glass beads was 4
All were performed under the same conditions as in Example 1 except that the amount was set to 00 g / liter. The result is as shown in FIG. 7, and the obtained surface had a color close to the original color tone of the material and was a good glossy surface, but the conditions under which a desired good surface can be obtained are relatively narrow. .

Example 6 Alumina particles having an average particle size of 14.5 μm and glass beads having an average particle size of 20 μm were used as abrasives, the concentration of alumina particles in a chiller was 150 g / liter, and the concentration of glass beads was 4
All were performed under the same conditions as in Example 1 except that the amount was set to 00 g / liter. The results are shown in FIG. 8, and substantially the same results as in Example 5 were obtained.

Example 7 The same conditions as in Example 5 were applied except that the concentration of alumina particles in the chiller was set to 500 g / liter. The results are shown in FIG. 9, and substantially the same results as in Examples 5 and 6 were obtained.

Example 8 The same conditions as in Example 6 were used except that the concentration of alumina particles in the chiller was set to 500 g / liter. The results are shown in FIG. 10, and substantially the same results as in Examples 5, 6 and 7 were obtained. As described above, in this example, the conditions for obtaining a good surface are narrowed as in the case of Examples 5, 6 and 7, but it can be said that this example is preferable in that a glossy surface having the original color tone of the material can be obtained.

Example 9 Only alumina particles having an average particle size of 8.0 μm were used as abrasive grains, the concentration of the alumina particles in the chiller was 800 g / liter, and the input air pressure was 2 kg / cm ² , and the number of projections was 3 times per side. The same conditions as in Example 1 were used except for the above. As a result, the color tone obtained was satin and matte, but the desired surface condition was obtained well.

Example 10 Only alumina particles having an average particle size of 20.0 μm were used as abrasive grains, the concentration of the alumina particles in the chiller was 400 g / liter, and the input air pressure was 2 kg / cm ² , and the number of projections was 3 times per side. The same conditions as in Example 1 were used except for the above. As a result, as in Example 9, the obtained color tone was matte and matte, but the desired surface condition was obtained well.

Example 11 The procedure of Example 5 was repeated except that the concentration of the glass beads in the chiller was 700 g / liter. The results obtained were substantially the same as in Example 5.

Example 12 The procedure of Example 5 was repeated except that the concentration of the glass beads in the chiller was 70 g / liter. The obtained results were slightly worse than those of Example 5, but were in a state that they could be regarded as almost the same.

Example 13 The procedure of Example 5 was repeated except that the concentration of alumina particles in the thriller was changed to 5 g / liter. Although the obtained results were slightly worse than those of Example 5, they were in a state that they could be regarded as substantially the same as in Example 12.

Comparative Example 1 The same conditions as in Example 1 were used except that glass beads having an average particle size of 10.0 μm were used as abrasive grains. The result is shown in FIG.
As shown in Fig. 1, the desired good surface condition could not be obtained.

Comparative Example 2 The same conditions as in Example 1 were used except that glass beads having an average particle size of 20.0 μm were used as abrasive grains. The result is shown in FIG.
As shown in Fig. 2, it can be seen that a good surface can be obtained and the conditions are extremely narrow. Also, input air pressure 3 kg /
The warp of the lead frame material which occurred when the number of times of projection was cm ² and the number of times of projection was 9 on each surface was the maximum among all the tests.

Comparative Example 3 The same conditions as in Example 5 were used except that the concentration of alumina particles in the chiller was 3 g / liter. The results obtained were somewhat worse than in the case of Comparative Example 1 shown in FIG.

Comparative Example 4 The same conditions as in Example 5 were used except that the concentration of the glass beads in the thriller was set to 50 g / liter. The obtained results were substantially the same as in Comparative Example 3, and the desired good surface condition could not be obtained.

Comparative Example 5 The same conditions as in Example 5 were used except that the concentration of alumina particles in the chiller was 700 g / liter. The obtained results are as shown in FIG. 13, and it can be seen that, as in the case of Comparative Example 2 shown in FIG. 12, although the range is different, the conditions under which a good surface can be obtained are extremely narrow.

[0040]

As described above, according to the present invention, the abrasive grains, water and air are mixed and sprayed on the front and back surfaces of the lead frame material in a direction substantially perpendicular to the respective surfaces. As a result, the impact force can be made moderate and it is possible to effectively remove the unevenness and burrs on the surface of the lead frame material. Therefore, unlike the conventional polishing method, the electrolytic polishing liquid and the chemical polishing liquid are not required, and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an apparatus used in each example of the present invention.

FIG. 2 is an explanatory diagram showing another example of the injection gun shown in FIG.

3A and 3B are diagrams showing an implementation result of Example 1, in which FIG. 3A shows a burr removal state, and FIG. 3B shows a smoothness of a treated surface and a deformation state of a lead frame material centering on a pattern portion. Shows.

4A and 4B are diagrams showing the results of implementation of Example 2, in which FIG. 4A shows the removal state of burrs, and FIG. 4B shows the deformation state of the lead frame material centering on the smoothness of the treated surface and the pattern portion. Shows.

5A and 5B are diagrams showing the results of implementation of Example 3, in which FIG. 5A shows the burr removal state, and FIG. 5B shows the smoothness of the treated surface and the deformation state of the lead frame material centering on the pattern portion. Shows.

6A and 6B are diagrams showing the results of Example 4, in which FIG. 6A shows the removal state of burrs, and FIG. 6B shows the smoothness of the treated surface and the deformation state of the lead frame material centering on the pattern portion. Shows.

7A and 7B are diagrams showing the results of Example 5, wherein FIG. 7A shows the removal status of burrs, and FIG. 7B shows the smoothness of the treated surface and the deformation status of the lead frame material centering on the pattern portion. Shows.

8A and 8B are views showing the results of Example 6, wherein FIG. 8A shows the removal status of burrs, and FIG. 8B shows the smoothness of the treated surface and the deformation status of the lead frame material centering on the pattern part. Shows.

9A and 9B are diagrams showing the results of Example 7, wherein FIG. 9A shows the removal state of burrs, and FIG. 9B shows the deformation state of the lead frame material centering on the smoothness of the treated surface and the pattern portion. Shows.

FIG. 10 is a diagram showing an implementation result of Example 8, (a)
Shows the removal state of burr, and (b) shows the smoothness of the treated surface and the deformation state of the lead frame material centering on the pattern portion.

FIG. 11 is a diagram showing an implementation result of Comparative Example 1, (a)
Shows the removal state of burr, and (b) shows the smoothness of the treated surface and the deformation state of the lead frame material centering on the pattern portion.

FIG. 12 is a diagram showing an implementation result of Comparative Example 2, FIG.
Shows the removal state of burr, and (b) shows the smoothness of the treated surface and the deformation state of the lead frame material centering on the pattern portion.

FIG. 13 is a diagram showing an implementation result of Comparative Example 5, (a)
Shows the removal state of burr, and (b) shows the smoothness of the treated surface and the deformation state of the lead frame material centering on the pattern portion.

[Explanation of symbols]

 1, 2 injection gun 1a, 2a nozzle A compressed air M mixed fluid

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadashi Nakano 1-6-1 Suehiro-cho, Ome-shi, Tokyo Within Sumitomo Metal Mining Co., Ltd. (72) Kensuke Sekiya 1-6-1 Suehiro-cho, Ome-shi, Tokyo Sumitomo Inside Metal Mining Co., Ltd. (72) Inventor Hitoshi Murayama 1-6-1 Suehirocho, Ome City, Tokyo Sumitomo Metal Mining Co., Ltd.

Claims (7)

[Claims] 1. A mixed fluid of abrasive grains, water and air is prepared,
A method for polishing a lead frame material, wherein the mixed fluid is sprayed onto the front and back surfaces of the lead frame material at least once in a direction substantially perpendicular to the front and back surfaces. 2. Alumina particles are used as the abrasive grains, and a particle concentration in a slurry containing the alumina particles is 80 to 80.
The method of polishing a lead frame material according to claim 1, wherein the polishing rate is 0 g / liter. 3. The method of polishing a lead frame material according to claim 2, wherein the upper limit of the average grain size of the abrasive grains is 1/3 of the lead interval and the lower limit is 8 μm. 4. A mixed grain of alumina particles and glass beads is used as the abrasive grains, and the slurry containing the mixed grains has an alumina particle concentration of 5 to 600 g / liter and a glass bead concentration of 70.
The method for polishing a lead frame material according to claim 1, wherein the polishing rate is set to ˜700 g / liter. 5. The upper limit of the average particle size of the abrasive grains is 1/3 of the lead interval, the lower limit of the alumina particles is 8 μm, and the lower limit of the glass beads is 10 μm. 4. The method for polishing a lead frame material according to item 4. 6. The alumina particles have an average particle size of 8 to 20.
The average particle size of the glass beads is 10 to 20 μm.
The method for polishing a lead frame material according to claim 2, wherein 7. A nozzle is used to spray the mixed fluid onto the lead frame material, and the distance between the lead frame material and the nozzle, the discharge pressure of the mixed fluid discharged from the nozzle, or the mixed fluid is set. The pressure of the abrasive grain slurry and the pressure of air for constituting, the discharge amount of the mixed fluid discharged from the nozzle, and the feed speed of the lead frame material are set to predetermined values determined in advance. 7. The method for polishing a lead frame material according to claim 1, wherein the lead frame material is polished.