JPH09181104A - Metal mold for sealing semiconductor resin and surface treatment thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow maintain good mold release property ranging over a plurality of molding even with no blending of a mold release agent with a mold resin material as well as with no spraying a mold releasecagent on the metal mold cavity surface. SOLUTION: In a state in which semiconductor chips are arranged inside metal mold cavities 4, 5, molding resin is injected into the metal mold cavities 4, 5 so as to form hard-plated films 6 on the upper and lower metal-mold cavity surfaces 4a, 5a to a metal mold for semiconductor resin sealing which seals semiconductor chips with molding resin. This hard-plated film 6 consists of a hard-plating material 8 containing mold release grains 7 being moreover evenly dispersed with mold release grains 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor resin encapsulating mold for arranging a semiconductor element in a mold cavity for resin encapsulation and a surface treatment method thereof.

[0002]

2. Description of the Related Art Conventionally, a ceramic package having a hollow structure has been adopted as a package form of a CCD image sensor or the like. However, the hollow ceramic package has problems such as high cost, water droplets adhering to the inner surface of the lid glass, large variation in dimensional accuracy, and difficulty in downsizing and weight reduction. Therefore, in recent years, in order to eliminate various problems in the ceramic package, a so-called clear mold package in which an optical element such as a CCD is sealed with a transparent resin has been put into practical use.
In this clear mold package, as with the existing black resin package, C is obtained by transfer molding.
A semiconductor element such as a CD is resin-sealed. However, in molding a clear mold package, if a mold release material is mixed with a mold resin material as in the case of a black resin package, the transparency of the package will be impaired. Therefore, the releasability when taking out the molded product from the molding die has become a serious problem. In particular, regarding the mold resin material, when considering the material composition and formulation to improve the moisture resistance and improve the adhesion to the metal (lead frame, chip, etc.), the mold releasability during molding becomes worse. There is a tendency. Therefore, conventionally, the mold cavity surface corresponding to the injection portion of the transparent resin is sprayed with a release agent to cope with the problem.

[0003]

However, when a mold release agent is sprayed on the mold cavity surface for resin sealing, a large amount of the mold release agent adheres to the surface of the mold resin (transparent resin) and becomes opaque. Become. Therefore, after spraying the mold release agent, many times of trial molding (hereinafter referred to as dummy shot) is performed in addition to the original production, such as injecting resin without disposing the semiconductor element in the mold cavity. When the amount of release agent adhered to the surface of the mold resin falls below an allowable level, it is necessary to perform the original molding with the semiconductor element placed in the mold cavity (hereinafter referred to as this shot). there were. In addition, the effect of spraying the release agent fades after only a few shots, so spraying the release agent and dummy shots must be repeated in an extremely short cycle. This has led to waste of material costs and a large increase in man-hours.

The present invention has been made to solve the above problems, and its purpose is to mix a mold release agent with a mold resin material or to spray the mold release agent on the mold cavity surface. It is an object of the present invention to provide a semiconductor resin encapsulating mold and a surface treatment method thereof, which can maintain a good mold releasability over a number of times of moldings, even if it is omitted.

[0005]

SUMMARY OF THE INVENTION In the present invention, a semiconductor resin for sealing a semiconductor element with a mold resin by injecting a mold resin into the mold cavity in a state where the semiconductor element is arranged in the mold cavity. In the mold for sealing, a problem is that a hard plating film made of a hard plating material containing release agent particles and having the release agent particles uniformly dispersed on the surface layer portion is formed on the mold cavity surface. It is used as a solution.

As a mold surface treatment therefor, a film forming step of forming a hard plating film containing release agent particles on the mold cavity surface by electroless nickel plating, and a mold cavity surface in vacuum. Is heated to the melting point temperature of the release agent particles, so that the release agent particles are uniformly dispersed in the surface layer portion of the hard plating film.

Therefore, according to the present invention, when the semiconductor element is placed in the mold cavity for resin sealing, the release agent particles dispersed in the surface layer of the hard plating film come into contact with the mold resin. It becomes a state. As a result, the adhesive strength of the mold resin to the mold cavity is reduced, and the releasability is correspondingly increased. Further, since the release agent particles are contained in the hard plating material,
When the molded product is taken out, it never adheres to the surface of the mold resin.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of an essential part showing an embodiment of a semiconductor resin sealing die according to the present invention, which shows a structure of a cavity portion of a transfer molding die. The molding die (semiconductor resin sealing die) 1 shown in FIG. 1 mainly includes an upper die 2 and a lower die 3. On the upper mold 2 and the lower mold 3, concave mold cavities 4 and 5 corresponding to the shape of the molded product (package shape) are formed so as to face each other. The mold cavities 4 and 5 serve as injection portions of mold resin during molding, and semiconductor elements (not shown) to be resin-sealed are arranged therein. Incidentally, the semiconductor element is generally placed in the mold cavities 4 and 5 while being mounted on the lead frame. In addition to the mold cavities 4 and 5 serving as resin injection parts, this type of molding die 1 also includes a pot serving as a molding material supply port, a plunger for moving the molding material under pressure, and a resin flow path. Are provided, a gate serving as a resin injection port to the mold cavities 4 and 5, and an ejector for taking out a molded product.

Here, in the molding die 1 of this embodiment, the hard plating film 6 is formed on each of the die cavities 4a and 5a for both the upper die 2 and the lower die 3. This hard plating film 6 is made of a hard plating material 8 containing release agent particles 7, and specifically, Ni
A metal material made of (nickel) or an alloy thereof containing a particle having a so-called releasing effect such as a fluororesin or a silicone resin is used. Further, in the thickness direction of the hard plating film 6, the release agent particles 7 are uniformly dispersed in the surface layer portion thereof. This is because when the mold cavities 4 and 5 are filled with the mold resin at the time of molding, the release agent particles 7 are brought into contact with the resin surface at a higher ratio. Further, in the present embodiment, in order to further enhance the releasability at the time of molding, the hard plating film 6 is formed up to the gate and runner portions communicating with the upper and lower mold cavities 4 and 5.

Next, the method for manufacturing the semiconductor resin encapsulating mold in this embodiment, including the surface treatment method, will be described with reference to FIG.
This will be described with reference to FIG. Here, FIG. 2 is a schematic process flow diagram relating to mold manufacturing, and FIG. 3 is a partial cross-sectional view showing changes in the coating state of the cavity surface in the process flow of FIG.

First, when manufacturing a die, Fe (iron) is used.
Various types of machining are applied to the die base material of the system to form cavities, gates, runners, pots, etc. at predetermined locations (S1: die working step). Next, the mold, which has undergone the entire shape processing, is heated to a quenching temperature corresponding to the base material and then rapidly cooled to be hardened (S2: heat treatment step). Next, as a pretreatment for the surface treatment, the oil and fat content on the mold surface is removed using a method such as a solvent degreasing method, an alkali degreasing method, an emulsion degreasing method (S3: degreasing treatment step). At this time,
It is recommended to remove other dirt components by washing with water. By the way, conventionally, after the degreasing treatment, the mold surface was subjected to hard chrome plating treatment, and at this point, it was a finished product.

On the other hand, in the present embodiment, after the degreasing treatment is finished, the base coating film 9 which is the base of the hard plating coating 6 (FIG. 1) described above is formed on the mold cavity surface by the electroless nickel plating treatment. (S4: Base film formation). As a result, the base coating film 9 (see FIG. 1) made of the electroless nickel plating film is formed on the mold cavity surface. The thickness of the base coating 9 is preferably about 5 to 20 μm.

Next, the mold (upper mold, lower mold) is immersed in an electroless nickel plating solution containing, for example, polytetrafluoroethylene (hereinafter referred to as PTFE) particles as release agent particles, and the reducing agent reduces the gold. Base coating for mold cavity 9
On top, a hard plating film containing the release agent particles is generated (S5: film forming step). At this time, the content of the release agent particles in the hard plating film is appropriately about 20% by weight in consideration of film quality hardness and releasability. The thickness of the hard plating film is 1 to 1
About 0 μm is appropriate. As a result, the hard plating film 6 containing the release agent particles 7 is formed on the mold cavity surface through the base film 9 as shown in FIG.

At this point, the hard plating film 6 containing the release agent particles 7 is formed on the mold cavity surface, but the release agent particles 7 are sparsely distributed on the surface layer of the hard plating film 6. Since they are dispersed, the dispersion density of the release agent particles 7 in the surface layer portion of the film is extremely low. Therefore, even if the molding die in this state is used for resin sealing of the semiconductor element, the desired release effect cannot be obtained because the contact ratio between the mold resin and the release agent particles 7 becomes low. Further, since the surface of the hard plating film 6 is a rough surface roughened by the release agent particles 7 scattered there, it is used for resin encapsulation of a semiconductor product which requires smoothness on the package surface. I can't.

Therefore, after the hard plating film 6 is formed on the die cavity surface, the irregularities on the surface of the hard plating film 6 are removed by lapping, whereby the surface of the hard plating film 6 is smoothed to a mirror surface level (S6: Surface polishing process). FIG. 3B shows the state of the coating surface after lapping. When handling a semiconductor product in which the resin surface after molding is not required to have smoothness, this surface polishing step (S6) may be omitted.

Subsequently, the mold cavity surface (entire mold is acceptable) is heated in vacuum to the melting point temperature of the mold release agent particles, whereby the mold release agent particles 7 are uniformly distributed on the surface layer of the hard plating film 6. Disperse (S7: vacuum annealing step). As a specific example of the vacuum annealing condition, the heating temperature is 350 to 370 ° C.
, The degree of vacuum was set to 10 ^-4 torr or less, and the processing time was set to about 2 hours. Among these conditions, the heating temperature depends on the composition of the release agent particles 7, and here, the heating temperature is PTFE.
Since particles are used, their melting point temperature is 35
It was set within the range of 0 ° C to plus 20 ° C.
The degree of vacuum is set to 10 ^-4 torr or less in order to prevent the oxidation of nickel due to the heating action. The treatment time was set in consideration of the time required for the release agent particles to be melted and sufficiently dispersed by the heat treatment, the time required for the film quality hardness of the hard plating film 6 to be sufficiently increased by the heat treatment, and the like. By performing such a vacuum annealing treatment, as shown in FIG. 3C, the release agent particles 7 melted by the heating action are uniformly dispersed in the surface layer portion of the hard plating film 6. Thereby, the hard plating film 6
The dispersion density of the release agent particles 7 in the surface layer can be remarkably increased.

When resin molding of a semiconductor element is performed using the molding die 1 manufactured in this way, the mold resin contacts the release agent particles 7 dispersed in the surface layer of the hard plating film 6. It will be in the state of doing. As a result, the adhesion strength of the mold resin to the mold cavities 4 and 5 is lowered, so that the releasability can be improved accordingly. Further, since the release agent particles 7 are embedded in the hard plating film 6, they do not adhere to the surface of the mold resin and are not peeled off when the molded product is taken out. Thereby, the surface of the mold resin can be prevented from being contaminated, and good mold releasability can be maintained by the interposition of the release agent particles 7 no matter how many times the resin sealing is repeated.

For reference, the evaluation results of releasability by the present applicant will be described below. First, as evaluation targets, a molding die having a chromium plating film formed on the mold cavity surface and a molding die having a nickel plating film containing release agent particles were prepared. As the surface condition of the coating, two patterns, that is, a matte surface and a mirror surface, were evaluated.
Further, as the mold resin, cresol novolac type and biphenyl type epoxy resins were used.

Then, when the mold releasability due to the difference in the coating film was actually examined by a tensile tester, in the case of the cresol novolac type epoxy resin, the chromium plating film was 8.0 Kg / cm ² (rough surface), 0 kg / cm
² (mirror surface), whereas the nickel plating film was 2.0 kg / cm ² (matte surface), 1.5 kg / cm
It was ² (mirror surface). On the other hand, in the case of biphenyl type epoxy resin, the chromium plating film is 16.0 Kg / c
m ² (matte surface) and 13.0 Kg / cm ² (mirror surface), whereas nickel plated coating 4.0 Kg / cm
² (pear ground) and 3.0 Kg / cm ² (mirror surface).
This result shows that the hard plating film 6 containing release agent particles
It has been proved that forming the mold on the mold cavity surface is extremely effective in improving the releasability during molding. By the way, in resin sealing by spraying a release agent,
Although it was possible to maintain good mold releasability only a few times with this shot, the molding die with the hard plating film 6 adopted in this embodiment is good even if this shot is performed about 10,000 times. The releasability could be maintained.

In the above embodiment, a fluorine resin such as PTFE is used as the material of the release agent particles, but other than this, for example, a silicone resin, a molding temperature at the time of resin sealing is used. It is sufficient that the resin has heat resistance to withstand, and has poor wettability with the mold resin (generally an epoxy resin).

[0021]

As described above, according to the present invention, a hard plating film containing release agent particles is formed on the mold cavity surface, and the release agent particles are evenly distributed on the surface layer of the hard plating film. Therefore, it is possible to maintain good mold releasability over a number of times of molding without sealing the mold resin surface due to the adhesion of a mold release agent in the conventional resin encapsulation of the semiconductor element. Become. This eliminates the need to spray the mold release agent onto the mold cavity surface in a short cycle and to repeat dummy shots after spraying, thus eliminating the waste of material costs and the increase in man-hours associated therewith. It is possible to improve the sex. In particular, in a clear mold package such as CCD (a package in which a semiconductor element is sealed with transparent resin),
Since it is possible to prevent stains on the surface of the mold resin due to the adhesion of the release agent, it is expected that the optical characteristics are improved. In addition, since it is not necessary to add a mold release agent to the mold resin material, the adhesion between the resin and the semiconductor element (chip) as well as the resin and the lead frame can be improved at the same time, which improves moisture resistance and package crack resistance. It is also possible to do.

[Brief description of the drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a semiconductor resin sealing die of the present invention.

FIG. 2 is a process flow chart for explaining an embodiment of a mold surface treatment method according to the present invention.

FIG. 3 is a partial cross-sectional view showing a change in film state in the process flow of FIG.

[Explanation of symbols]

 4, 5 Mold cavity 4a, 5a Mold cavity surface 6 Hard plating film 7 Release agent particles 8 Hard plating material

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B29C 45/26 9268-4F B29C 45/26

Claims (3)

[Claims] 1. A semiconductor-resin-sealing mold for sealing the semiconductor element with the molding resin by injecting a molding resin into the molding cavity in a state where the semiconductor element is placed in the molding cavity, A semiconductor resin encapsulation characterized by comprising a hard plating material containing release agent particles, wherein a hard plating film in which the release agent particles are uniformly dispersed is formed on the surface of the mold cavity surface. Stopping mold. 2. A surface of a semiconductor resin-sealing mold for sealing the semiconductor element with the mold resin by injecting a mold resin into the mold cavity with the semiconductor element arranged in the mold cavity. A treatment method, a film forming step of forming a hard plating film containing release agent particles on the die cavity surface by electroless nickel plating, A surface treatment method for a semiconductor resin encapsulating mold, which comprises a vacuum annealing step of uniformly dispersing the release agent particles in a surface layer portion of the hard plating film by heating to a melting point temperature of the particles. . 3. The surface treatment of a semiconductor resin encapsulating mold according to claim 2, wherein after the film forming step, the surface of the hard plating film is polished smoothly and then the vacuum annealing step is performed. Method.