JPH11121669A - Lead forming material and method for surface processing for its improved tight contact with resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve tight-contact characteristics to a resin sealing material by growing an oxide layer at high temperature and humidity after a lead forming material of pure copper or copper alloy is pickled in hydrogen peroxide- added dilute sulfuric acid. SOLUTION: A lead formation material 1 is submerged in a pickling agent to partially dissolve its surface, and left alone at high temperature and humidity to form an oxide film comprising minute ruggedness. Here, the thickness of the oxide film should be 500-2000 nm. The pickling agent I preferred to be a hydrogen peroxide-added dilute sulfuric acid wherein H2 SO4 of concentration 5-20% is added with H2 O2 by 1-6%, for even growth of ruggedness. As for growth condition at high temperature and humidity after submerged in the pickling agent, temperature of 60-120 deg.C and relative humidity of 65% or higher is preferred. With an oxide film comprising fine ruggedness, thus obtained, tight-contact characteristics to an epoxy resin sealing material 2 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead forming material and a surface treatment method for improving resin adhesion. More specifically, the present invention relates to a lead forming material, for example, a lead frame or TAB foil of pure copper or a copper alloy, and a surface treatment method for improving the resin adhesion of the surface thereof.

[0002]

2. Description of the Related Art In recent years, the increase in semiconductor device production has been remarkable.

In general, in manufacturing a semiconductor device, first, a semiconductor chip is mounted on a lead frame, then the lead frame and the semiconductor chip are wire-bonded with a gold wire or the like, and then the semiconductor chip mounting portion is made of a ceramic sealing material or It is manufactured by sealing with an epoxy resin sealing material.

Among these, epoxy resin sealing materials are frequently used as sealing materials from the viewpoints of workability, productivity and low cost.

However, when the epoxy resin-sealed semiconductor element is soldered to a printed circuit board, cracks may occur in the epoxy resin layer sealing material.

A factor involved in the generation of cracks is water that has penetrated into the inside from the boundary between the lead frame and the epoxy resin sealing material. The amount of water penetration increases as the adhesion between the lead frame and the epoxy resin sealing material is poor.

That is, in an epoxy resin encapsulated semiconductor device having poor adhesion between a lead frame and an epoxy resin encapsulant,
Moisture invades from the interface between the lead frame and the epoxy resin encapsulant, and the infiltrated water evaporates and expands due to the heat of the high-temperature solder when soldering to the printed circuit board. It is considered that cracks occur in the stopper layer.

For this reason, it is desired to improve the resin adhesion of the surface of a lead forming material, for example, a lead frame or TAB foil of pure copper or a copper alloy.

Although a method of forming fine irregularities on the surface of a lead frame by a physical method and thereby improving the resin adhesion on the surface has been studied, this method can form fine and uniform irregularities. Have difficulty.

On the other hand, epoxy resin encapsulants have been developing low-hygroscopic base epoxy resins and examining low-hygroscopic fillers, but there is no definitive solution.

On the other hand, the epoxy resin encapsulated semiconductor element is heated to about 200 ° C. in the air before soldering to a printed circuit board, that is, at the stage of wire bonding the lead frame and the semiconductor chip with a gold wire or the like. It has been found that an oxide film is formed on the surface of the frame. Since these oxide films are randomly formed in the atmosphere, they have uneven thickness and low strength. For this reason, even if the epoxy resin sealing material adheres to these oxide films, there is a concern that the epoxy film is peeled off at the interface of the oxide film, and that moisture permeates from the peeled interface.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to improve the adhesion to a resin sealing material. An object of the present invention is to provide an excellent lead forming material and a surface treatment method for improving its resin adhesion.

[0013]

The gist of the present invention lies in the following two points.

(1) In a lead forming material formed by forming an oxide layer on the surface of a lead forming material made of pure copper or a copper alloy, the oxide layer is formed by peroxidizing the lead forming material made of pure copper or a copper alloy. A lead forming material characterized by being pickled with hydrogenated dilute sulfuric acid and then grown under high temperature and high humidity.

(2) The surface of a lead forming material made of pure copper or a copper alloy is immersed in dilute sulfuric acid with hydrogen peroxide to perform a surface treatment, and then left in the atmosphere at high temperature and high humidity to grow an oxide film. A surface treatment method for improving resin adhesion of a lead forming material, characterized by comprising:

In the first invention, the pickling solution has a concentration of 5%.
To 20% H ₂ SO _4, is preferably a H ₂ O ₂ is hydrogen peroxide added dilute sulfuric acid composed in addition 1-6%.

Here, the concentration of H ₂ SO ₄ is 5-20.
The reason why the percentage is set to 5% is that if it is 5% or less, the unevenness growth property of the oxide film under high temperature and high humidity after immersion in the pickling solution becomes poor.

Conversely, when the concentration of H ₂ SO ₄ is not less than 20%, the unevenness of the oxide film after immersion in the pickling solution under high temperature and high humidity becomes too large, and as a result, the oxide film becomes This is because it becomes brittle.

The reason why the addition amount of H ₂ O ₂ is set to 1 to 6% is that if it is 1% or less, the oxide film becomes poor in growth of unevenness under high temperature and high humidity after immersion in a pickling solution. That's why.

Conversely, if the added amount of H ₂ O ₂ is 6% or more, the uneven growth of the oxide film under high temperature and high humidity after immersion in the pickling solution becomes non-uniform.

The temperature of the pickling solution is suitably from 5 to 40 ° C. This is because when the temperature of the pickling solution is 5 ° C or less, the solubility is slow,
Conversely, if the temperature is higher than 40 ° C., the solubility is too fast.

The immersion time in the pickling solution is suitably from 5 to 20 seconds. This is because if the immersion time is less than 5 seconds, the dissolution is insufficient, and if the immersion time is more than 20 seconds, poor discoloration is likely to occur.

Further, in the present invention, the growth conditions under high temperature and high humidity after immersion in the pickling solution are as follows.
It is preferable that the temperature and the relative humidity are 65% or more.

As described above, according to the present invention, first, a lead forming material is immersed in an pickling solution to partially dissolve the surface, and then left under high temperature and high humidity to form an oxide film having fine irregularities. An object of the present invention is to improve the adhesiveness with an epoxy resin sealing material by using an oxide film having fine irregularities formed.

In the present invention, the thickness of the oxide film is 15
100-2000 nm is appropriate. This is because the effect of improving the resin adhesion is small when the thickness of the oxide film is 1500 nm or less, and the effect of improving the resin adhesion is not proportional to the thickness when the thickness is 2000 nm or more.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples and comparative examples of a lead forming material and a method for improving the resin adhesion thereof according to the present invention will be described below.

Example 1 Lead Forming Material The lead forming material used in Example 1 is a lead frame having a thickness of 0.125 mm obtained by rolling JIS Class 1 oxygen-free copper.

Next, the lead frame was degreased and washed with acetone.

Next, a plurality of lead frame test pieces having a width of 30 cm, a depth of 30 cm and a thickness of 0.125 mm were cut out from the lead frame degreased and washed with acetone.

The concentration as immersion treatment pickling solution in the pickling solution with 10% H ₂ SO ₄ 3% of H ₂
Hydrogen peroxide-added diluted sulfuric acid was prepared by mixing O ₂ . The temperature of the diluted sulfuric acid with hydrogen peroxide was adjusted to 25 ° C. before use.

The lead frame test piece was immersed in the dilute sulfuric acid added with hydrogen peroxide for 10 seconds.

Next, the lead frame test piece taken out of the pickling solution was rinsed with pure water, and then blow-dried with dry nitrogen gas.

Formation of Oxide Film on Lead Frame Specimen under High Temperature and High Humidity After immersion in the pickling solution, the rinsed and dried lead frame specimens are placed in a thermo-hygrostat at a temperature of 80 ° C. and a relative humidity of 93%. And then left under the conditions for 8 hours.

After a lapse of 8 hours, the relative humidity in the thermo-hygrostat was reduced to 50%, and then a lead frame test piece was taken out.

Simulated Bonding Heat Treatment of Lead Frame Specimen Next, the lead frame specimen obtained above was subjected to a heat treatment at 170 ° C. for 2 hours and at 250 ° C. for 1 minute in the atmosphere for simulated bonding heat treatment.

Preparation of Model Semiconductor Device Next, on the lead frame test piece heat-treated above,
The epoxy resin sealing material was sealed.

Next, the model semiconductor device of Example 1 was prepared by heating at 180 ° C. for 6 hours to cure the epoxy resin sealing material.

FIG. 1 is a perspective view of the model semiconductor device of the first embodiment thus obtained.

In FIG. 1, 1 is a lead frame test piece,
2 is an epoxy resin sealing material, and the arrow is the tensile direction of the peel strength test.

In FIG. 1, the epoxy resin sealing material 2 has a bottom area of 2.0 mm × 2.0 mm, a height of 6 mm, and a top area of 1.2 mm × 1.2 mm. Therefore, the contact surface between the lead frame test piece 1 and the epoxy resin sealing material 2 is 2.0 mm × 2.0 mm, which is the same as the bottom area.

Moisture Absorption Treatment of Model Semiconductor Device of Example 1 Some of the model semiconductor devices obtained above are:
The sample was placed in a thermo-hygrostat at a temperature of 85 ° C. and a relative humidity of 85% for 72 hours to be subjected to a hygroscopic degradation treatment.

Example 2 Lead Forming Material The lead forming material used in Example 2 was a copper alloy C194 material (a copper alloy containing 2.3% Fe, 0.1% Zn and 0.03% P). This is a 0.125 mm-thick lead frame obtained by rolling.

Next, the lead frame was degreased and washed with acetone.

Next, a plurality of lead frame test pieces having a width of 30 cm, a depth of 30 cm, and a thickness of 0.125 mm were cut out from the lead frame degreased and washed with acetone.

Immersion treatment in pickling solution The same concentration as that used in Example 1 was used as the pickling solution.
% H ₂ SO ₄ and 3% H ₂ O ₂ were mixed and adjusted to 25 ° C. with hydrogen peroxide-added dilute sulfuric acid.

The lead frame test piece was immersed in the dilute sulfuric acid added with hydrogen peroxide for 10 seconds.

Next, the lead frame test piece taken out of the pickling solution was rinsed with pure water and then blow-dried with dry nitrogen gas.

Formation of Oxide Film under High Temperature and High Humidity of Lead Frame Specimen After immersion in the pickling solution, the rinsed and dried lead frame specimen is placed in a constant temperature and humidity chamber at a temperature of 80 ° C. and a relative humidity of 93%. And then left under the conditions for 8 hours.

After a lapse of 8 hours, the relative humidity in the thermo-hygrostat was reduced to 50%, and then a lead frame test piece was taken out.

Simulated Bonding Heat Treatment of Lead Frame Specimen Next, the lead frame specimen obtained above was subjected to a heat treatment at 170 ° C. for 2 hours and at 250 ° C. for 1 minute in the atmosphere for a simulated bonding heat treatment.

Preparation of Model Semiconductor Element Next, on the lead frame test piece heat-treated above,
The epoxy resin sealing material was sealed.

Next, the model semiconductor device of Example 2 was prepared by curing the epoxy resin sealing material by heating at 180 ° C. for 6 hours.

Moisture Absorption Treatment of Model Semiconductor Device of Example 2 For some of the model semiconductor devices obtained above,
The sample was placed in a thermo-hygrostat at a temperature of 75 ° C. and a relative humidity of 80% for 10 hours to be subjected to a hygroscopic degradation treatment.

(Comparative Example 1) Lead Forming Material The lead forming material used in Comparative Example 1 was the same JIS as in Example 1.
This is a 0.125 mm-thick lead frame obtained by rolling Type 1 oxygen-free copper.

Next, the lead frame was degreased and washed with acetone in the same manner as in Example 1.

Next, a lead frame degreased and washed with acetone, as in Example 1, 30 cm wide × 30 cm deep × 0.12 thickness
A plurality of 5 mm lead frame test pieces were cut out.

Simulated Bonding Heat Treatment of Lead Frame Specimen Next, the lead frame specimen obtained above was subjected to a heat treatment at 170 ° C. for 2 hours and at 250 ° C. for 1 minute in the atmosphere for a simulated bonding heat treatment.

Preparation of Model Semiconductor Element of Comparative Example 1 Next, on the lead frame test piece heat-treated as described above,
The epoxy resin sealing material was sealed.

Next, by heating at 180 ° C. for 6 hours to cure the epoxy resin sealing material, a model semiconductor device of a comparative example was prepared as shown in FIG.

The moisture absorption treatment of the model semiconductor device of Comparative Example 1 For some of the model semiconductor devices obtained above,
The sample was placed in a thermo-hygrostat at a temperature of 85 ° C. and a relative humidity of 85% to be subjected to a moisture absorption deterioration treatment.

Comparative Example 2 Lead Forming Material The lead forming material used in Comparative Example 2 was the same copper alloy C194 material as in Example 2 (2.3% Fe, 0.1% Zn, 0.03%).
% P obtained by rolling copper alloy containing 0.1P
mm lead frame.

Next, the lead frame was degreased and washed with acetone in the same manner as in Example 1.

Lead frame test piece Next, a lead frame degreased and washed with acetone, 30 cm in width × 30 cm in depth × 0.12 thickness as in Example 1.
A plurality of 5 mm lead frame test pieces were cut out.

Simulated Bonding Heat Treatment of Lead Frame Specimen Next, the lead frame specimen obtained above was subjected to a heat treatment at 170 ° C. for 2 hours and at 250 ° C. for 1 minute in air to perform a simulated bonding heat treatment.

Preparation of Model Semiconductor Device of Comparative Example 2 Next, on the lead frame test piece heat-treated above,
The epoxy resin sealing material was sealed.

Next, by heating at 180 ° C. for 6 hours to cure the epoxy resin sealing material, a model semiconductor device of Comparative Example 2 was prepared as shown in FIG.

The moisture absorption treatment of the model semiconductor device of Comparative Example 2 For some of the model semiconductor devices obtained above,
The sample was placed in a thermo-hygrostat at a temperature of 75 ° C. and a relative humidity of 80% for 10 hours to be subjected to a hygroscopic degradation treatment.

(Measurement of Peel Strength of Model Semiconductor Elements of Examples and Comparative Examples) Next, Examples 1 and 2 and Comparative Examples 1 and 2
As shown in FIG. 1, a force was applied from the shearing direction to the model semiconductor element not subjected to the moisture absorption degradation treatment and the model semiconductor element subjected to the moisture absorption degradation treatment, and the load when the epoxy resin sealing material 2 was peeled off was determined.

(Peeling Test Results) Table 1 shows the peeling test results of the model semiconductor elements of the examples and the comparative examples.

[0070]

[Table 1]

As can be seen from Table 1, the peel strength of the model semiconductor element of Comparative Example 1 was not subjected to moisture absorption deterioration treatment.
Low 3MPa and 2.2M after moisture absorption and deterioration treatment
Pa and lower than that.

Further, the peel strength of the model semiconductor element of Comparative Example 2 was 3.5 MPa for the case where no moisture absorption deterioration treatment was performed, and 2.9 MPa for the case where the moisture absorption deterioration treatment was not performed.

On the other hand, the peel strength of the model semiconductor element of Example 1 was 7.6 MPa without moisture absorption deterioration treatment.
It was as high as 7.4 MPa even after moisture absorption and degradation treatment.

The peel strength of the model semiconductor element of Example 2 was as high as 9.3 MPa without moisture absorption and degradation, and as good as 8.6 MPa with moisture absorption and degradation.

(Surface Observation of Lead Frame Specimen) Next, for the lead frame specimen of Example 1, the surface at the next stage was observed with a scanning electron microscope, and the SEM image was taken.

(A) Lead frame at the stage of degreasing and washing with acetone (lead frame at the stage of Example 1) (b) Lead frame at the stage of immersion treatment in the pickling solution (at the stage of the stage of Example 1) (C) Lead frame at the stage of high temperature and high humidity treatment in a constant temperature and humidity chamber (lead frame at the stage of Example 1) FIG. 2 shows lead at the stage of degreasing and washing with acetone of (A) above. 5 shows an SEM image of the surface of the frame.

As can be seen from FIG. 2, on the surface of the lead frame at the stage of degreasing and washing with acetone, there are longitudinal streaks and transverse cracks generated in the rolling process, and these are uneven and brittle. It has a structure.

FIG. 3 shows an SEM image of the surface of the lead frame at the stage after the pickling treatment (b).

As can be seen from FIG. 3, the surface of the lead frame subjected to the pickling treatment is flattened by the pickling solution by dissolving the vertical streaks and the horizontal cracks in the surface.

FIG. 4 shows an SEM image of the surface of the lead frame at the stage of the high-temperature and high-humidity treatment in the (iii) constant temperature and humidity chamber.

As can be seen from FIG. 4, a dense and uneven oxide film is formed on the surface of the lead frame after the high temperature and high humidity treatment. This dense and uneven oxide film exerts an anchor effect of close contact with the epoxy resin sealing material.

FIG. 5 shows an SEM image of the surface of the lead frame which was pickled with a rinsing liquid (a pickling liquid obtained by adding a small amount of hydrochloric acid to a mixed acid of nitric acid and sulfuric acid).

As can be seen from FIG. 5, the surface of the lead frame that has been pickled with the rinsing liquid is severely dissolved. This is because the rinsing solution is a strong mixed acid.

FIG. 6 shows an SEM image of the surface of the lead frame at the stage where the lead frame pickled with a rinsing solution is further subjected to high temperature and high humidity treatment in a constant temperature and humidity chamber.

As can be seen from FIG. 6, the surface of the lead frame which has been pickled with a rinsing solution and then subjected to high temperature and high humidity treatment is smooth, and has a dense and uneven shape like the surface of the lead frame of Example 1. No oxide film was seen.

[0086]

According to the lead forming material of the present invention and its surface treatment method for improving resin adhesion, a lead forming material having excellent adhesion to a resin sealing material can be obtained, which is industrially useful. .

[Brief description of the drawings]

FIG. 1 is a perspective view of a model semiconductor device of the present invention.

FIG. 2 shows an SEM image of the surface of a lead frame at the stage of degreasing and washing with acetone in the surface treatment method for improving resin adhesion of a lead forming material according to Example 1 of the present invention.

FIG. 3 shows an SEM image of the surface of the lead frame at the stage of pickling in the surface treatment method for improving resin adhesion of a lead forming material according to Example 1 of the present invention.

FIG. 4 shows an SEM image of the surface of a lead frame at the stage of high-temperature and high-humidity treatment in a constant-temperature and constant-humidity chamber in the surface treatment method for improving resin adhesion of a lead forming material according to Example 1 of the present invention. .

FIG. 5 shows an SEM image of the surface of a lead frame that has been pickled with a rinsing solution.

FIG. 6 shows an SEM image of the surface of the lead frame at a stage where the lead frame pickled with a rinse solution is further subjected to high temperature and high humidity treatment in a constant temperature and humidity chamber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead frame test piece 2 Epoxy resin sealing material

Claims (5)

[Claims] A lead forming material comprising an oxide layer formed on a surface of a lead forming material made of pure copper or a copper alloy,
The lead formation is characterized in that the oxide layer is formed by subjecting the lead forming material made of pure copper or a copper alloy to a pickling treatment with dilute sulfuric acid added with hydrogen peroxide and then growing it at a high temperature and a high humidity. Wood. 2. The lead forming material according to claim 1, wherein the thickness of the oxide film is 500 to 2000 nm. 3. The surface of a lead forming material made of pure copper or a copper alloy is immersed in dilute sulfuric acid with hydrogen peroxide to perform a surface treatment.
A surface treatment method for improving the resin adhesion of a lead forming material, wherein an oxide film is grown by leaving the film in an atmosphere at high temperature and high humidity. 4. The dilute sulfuric acid to which hydrogen peroxide is added has a concentration of 5 to 20.
% Of claim 3 resin adhesion of the lead forming material according improved surface treatment method characterized by the H ₂ SO ₄ in which the H ₂ O ₂ formed by adding 1-6%. 5. The growth conditions under high temperature and high humidity after immersion in the pickling solution are as follows: a temperature of 60 ° C. to 120 ° C. and a relative humidity of 65%.
4. The surface treatment method for improving resin adhesion of a lead forming material according to claim 3, wherein: