JPH10235653A - Resin molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive resin molding die, which can be shaped in a shor time working, without lowering wear resistance. SOLUTION: By machining a mold, out of which a gate port 33 as a space for connecting a cavity 32 and a gate 31 is produced, with a tool steel into a predetermined shape, a gate piece 41 is produced. By executing a nitriding treatment to the gate piece 41, a hardened layer 42, the hardness of which is equal to that of cemented carbide, is produced on the surface of the gate piece 41. Finally, by assembling the gate pieces 42 in a bottom mold 52 in order to form a mold 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molding die used for molding a package of a semiconductor device with a resin.

[0002]

2. Description of the Related Art In the process of assembling a semiconductor device, a semiconductor element is packaged (sealed) to protect it from the outside. There are various packaging methods,
For example, plasticizing thermosetting resin such as epoxy resin,
Transfer molds, in which this is injected into a heated mold cavity to form a package, are often used because they are inexpensive. FIG. 9 shows a cross-sectional front view of a mold 10 used for transfer molding. This mold 10
Are separated into an upper mold 1 and a lower mold 2. The upper mold 1 includes an upper mold cavity block 12 forming an upper portion of the cavity 32 , a cull block 13 forming a cull 36, and a base block 11 holding the upper mold cavity block 12 and the cull block 13. It is composed of Mold 10
FIG. 8 shows a partial perspective view of the lower mold 2. The lower mold cavity block 22 which forms the lower part of the cavity 32 is shown in FIG.
And a pot block 23 into which a cylindrical body 28 forming a pot 35 in which the plunger 7 is provided is inserted, and a holder base 21 for holding these. The lower mold cavity block 22 has a pot 3
Groove 2 serving as gate 31 communicating between cavity 5 and cavity 32
2a is formed.

When a package is formed using this mold 10, first, as shown in FIG. 9, a lead frame F on which a semiconductor element 5 is mounted on a die pad Fa is set in a lower mold 2, and further, as shown in FIG. Then, a resin 6 such as an epoxy resin is set in the pot 35 , and the upper mold 1 and the lower mold 2 are aligned. When the resin 6 is set in the pot 35 , the resin 6 immediately becomes a fluid gel due to the heat of the heated pot. Next, when pressing the resin 6 becomes the gel by the plunger 7, through the gate opening 33 resin 6 is connected space between gate 31 and gate 31 and the cavity 32, it is injected into the cavity 32. By heating and pressing the resin 6 for a certain period of time, the polymer structure of the resin 6 changes, and a plastic package that does not melt even when heat is applied again is formed.

[0004] Figure 10 is a partially enlarged cross-sectional view of a gate opening 33, the gate opening 33, in order to suppress the occurrence of burrs of the package to be formed is smaller. That is, the portion of the mold 10 forming the gate port 33 becomes the ridge 24 in the groove 22a, and the gate port 33 is reduced. However, as the mold 10 is used, the tip of the ridge portion 24 is gradually shaved due to the flow rate when the resin 6 is injected into the cavity 32 , and becomes larger as shown by the dotted line in FIG. Wear out. Therefore,
Prolonged use causes problems such as a large amount of burrs occurring in the package.

Conventionally, a mold for forming a gate port 33 (and a portion for forming the gate 31 ), which is a connection space between the gate 31 and the cavity 32 , is shown by a dashed line in FIGS. As described above, the lower mold cavity block 22 is separated from the lower mold block 22 (hereinafter, referred to as a gate piece 25). The other part of the mold 10, that is, the gate piece 25
The other parts are formed of an inexpensive material that is easy to process, for example, alloy tool steel. However, the abrasion-resistant gate piece 25 is formed of a wear-resistant cemented carbide. However, conversely, since the gate piece 25 is formed of a hard cemented carbide, it takes time to process the gate piece 25 into a predetermined shape, which is expensive. That is, the mold 10 having the gate piece 25 formed of a cemented carbide is
Although it has excellent wear resistance and a long service life, there is a problem that it takes a very long time to complete and is expensive.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resin molding die which has excellent friction resistance, is inexpensive, and can be manufactured in a short time.

[0007]

An object of the present invention is to provide a plunger (7) for pressurizing a molding material (for example, Embodiment 6; the same applies hereinafter), and at least the plunger (7) provided therein. A pot ( 35 ) for supplying the molding material (6), a cavity ( 32 ) into which the molding material (6) is injected to seal the semiconductor element (5), and a molding material (6) from the pot ( 35 ) ) To the above cavity ( 32 )
In the resin molding die having the gate ( 31 ) leading to the side, the portions (41, 51) forming the connection space ( 33 ) between the gate ( 31 ) and the cavity ( 32 ) are
The problem is solved by a resin molding die (40, 50) characterized in that after processing into a predetermined shape, the portions (41, 51) forming the connection space ( 33 ) are subjected to nitriding treatment.

[0008] By using a mold having such a structure, the surface of a portion that is worn by resin injection or the like is nitrided, although the time required for processing into a predetermined shape can be shortened. (Although it depends on the material of the base material to be nitrided,) a hardness almost equal to that of a super-hard metal can be obtained, and a mold having high wear resistance can be obtained. Therefore, the processing time can be shortened without lowering the wear resistance, and the price can be reduced.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A portion of a mold which forms a connection space between a gate and a cavity is processed into a predetermined shape and then subjected to nitriding. Therefore, the portion of the mold that forms a connection space between the gate and the cavity, which is heavily worn by resin injection or the like, has a hardness similar to that of a super-hard metal and has good wear resistance. Also, when processing into a predetermined shape, since the hardness of the part is not so hard, it is possible to easily process,
Processing time can be shortened. Therefore, the mold can be produced in a short time and at low cost. Furthermore, since the nitriding treatment is used to harden the surface, the amount of deformation of the mold after the treatment is small, and a predetermined shape can be easily obtained.

Further, if the mold at the portion forming the connection space between the gate and the cavity can be separated from the mold at another portion (for example, a cavity block or a pot block forming the majority of the cavity), When the mold at the portion forming the connection space between the gate and the cavity becomes worn due to long-term use, only the mold at this portion needs to be replaced, so that the life of the entire mold is further extended. be able to.

[0011] Further, the mold at the portion forming the connection space between the gate and the cavity may be made of any one of tool steel, stainless steel, nitrided steel and structural steel used for improving wear resistance in the nitriding treatment. If it is formed of a material, the wear resistance of the mold can be further improved.

If the depth of the hardened layer formed by the nitriding treatment is set to several tens μm to several hundred μm from the surface, the inner material of the nitrided material appears even if it is slightly worn. And a long life can be maintained. In order to obtain a depth of several tens μm to several hundred μm of the hardened layer, “CaC” on page 349 to page 353 of Vol.
Nitriding Technology Using Pyrolysis Reaction of Lime Nitrogen (CaCN ₂ ), as disclosed in “New Technology for Nitriding of Steel Using Pyrolysis of N ₂ and Its Features” (Hideto Fujita and four others). With the use of the treatment, the hardened layer can not only obtain the above-mentioned depth but also can be formed very uniformly and evenly.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. Parts similar to those in the above-described conventional example are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a mold 4 according to a first embodiment of the present invention.
0 is a front sectional view, and FIG. 2 is [2]-in FIG.
[2] FIG. 2 is a partial plan view in a line direction. The mold 40 is a multi-plunger mold having a plurality of pots 35 for supplying the resin 6. The lower mold 2 ′ of the mold 40 of the present embodiment mainly includes a lower mold cavity block 52, a pot block 23,
It comprises a gate piece 41 and a holder base 21 for holding these. Lower mold cavity block 5
2 has a space 32a which is a lower part of the cavity 32 ,
The shape is such that the gate piece 41 is provided inside. On the other hand, the gate-piece 41 is a mold portion forming a gate 31 and a gate 31 and a gate opening 33 which is connected to the space between the cavity 32, separated from the lower die cavity block 52 which forms a cavity 32 It is formed separately so that it is possible. This gate piece 41
Has a cylindrical shape having a surface 41b, a part of which is cut obliquely, as shown in FIG.
Form a part of the cavity 32 . Further, in the center of the gate piece 41, a groove 41a forming the gate 31 is formed.
Are formed. The groove 41a is provided in the cavity 3
The two sides are inclined upward to form the ridges 44, and the upper mold 1
The gate opening 33 has a small space when combined with.

The gate piece 41 of the present invention is formed as follows. For example, SKD61 (Rockwell hardness HRC = 4)
A gate piece 41 ′ having a shape as shown in FIG. At this time, since the hardness of the gate piece 41 'is not so high, it can be easily processed. Next, the gate piece 41 'is subjected to a nitriding treatment. This nitriding treatment is performed, for example, as follows.
As shown in FIG. 4, granular lime nitrogen (main component is CaCN) filled in a muffle 61 provided in a furnace body 66.
₂ ) The gate piece 41 'is buried and sealed in 62.
After the pressure inside the muffle 61 is reduced to about 20 Torr by a vacuum pump (not shown) connected via a vacuum valve 63, ammonia and nitrogen as a carrier gas are introduced into the muffle 61 from a supply pipe 64. (And this is exhausted from the exhaust pipe 65), and is heated and held at, for example, 500 ° C. By this nitriding treatment, a hardened layer 42 indicated by hatching in FIG. 1 is generated on the surface of the gate piece 41 ′, and the gate piece 41 is obtained. In this nitriding process, the gate piece 41 ′ before the nitriding process is used.
Even if the shape of
_By means of ₂ , nitriding proceeds stably and very uniformly. The depth from the surface of the hardened layer 42 generated by the nitriding treatment is several tens μm to several hundreds μm (depending on the nitriding treatment time). Also, the hardness of the cured layer,
That is, the hardness of the surface of the gate piece 41 is about Vickers hardness H _V = about 1000 to 1300, which is equivalent to the hardness of a cemented carbide.

The gate piece 41 thus formed is
The lower mold 2 ′ is formed by combining the lower mold cavity block 52, the holder base 21, and the like.

When a resin package is molded using the mold 40, first, as shown in FIG. 1, a lead frame F having a die pad Fa on which a semiconductor element 5 is mounted is placed in a cavity 32 . Set, and
The resin 6 is set in the heated pot 35 . When the resin 6 is set, the pot 35 for example 18
It is heated to about 0 ° C. and melts after a few seconds to form a gel. The gel-like resin 6 is pressed by the plunger 7, and the cavity is formed through the gate 31 and the gate port 33.
32 is injected with the resin 6. Then, the plastic package is molded by heating and pressurizing at a predetermined time, for example, at the above temperature.

In this embodiment, the cavity 32 and the gate 3
When the gate piece 41 forming the gate port 33 , which is the connection space with the first , is processed into a predetermined shape, the material is not difficult to process, so the processing is inexpensive and can be performed in a short time. I can do it. Then, after processing, a nitriding treatment can be performed to make the surface the same hardness as the cemented carbide. Therefore, the gate piece 41, which is a mold for forming the gate opening 33 , has excellent wear resistance.

Next, a second embodiment of the present invention will be described with reference to FIG. 5. Parts similar to those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The front sectional view of the mold 50 of this embodiment is substantially the same as that of the above embodiment shown in FIG. FIG. 5 is a partial front view as seen from the same direction as FIG. 2 of the above embodiment. The mold 50 of this embodiment is different from the above embodiment in the shapes of the gate piece 51 and the lower mold cavity block 52 'constituting the lower mold 2 ". 5, it has a rectangular shape formed with a plurality of spaces 32a that are the lower part of the cavity 32. On the other hand, the gate piece 5 of the embodiment is formed.
As shown in FIG. 6, 1 has a rectangular shape having a surface 51b with a part cut off obliquely. Further, a plurality of grooves 51 a forming the gate 31 are formed in the gate piece 51. Further, similarly to the above-described embodiment, the groove 51a has a ridge portion 54 in which the cavity 32 side is inclined upward, and when combined with the upper mold 1, the gate opening 3 is formed.
The shape of the space 3 becomes smaller, and the width decreases toward the cavity 32 as shown in FIG.

The gate piece 51 is formed in the same manner as the gate piece 41 of the above embodiment. For example, S
After being formed in a tool steel such as KD11 (Rockwell hardness HRC = 55-60) into a shape as shown in FIG. Is performed by the method described above, and a hardened layer of about several tens μm to several hundred μm is formed on the surface.
When using SKD11 as a material, the Vickers hardness H _V, (depending on the nitriding time) approximately 900
It is about 1300, and a hardness equivalent to that of a cemented carbide can be obtained in the same manner as in the above embodiment. And this gate piece 51
Is incorporated in the lower mold 2 ″ similarly to the above embodiment.

Also in the present invention, when processed into a predetermined shape, since the hardness is not so high, the processing can be easily performed. Then, after being processed, a hardened layer is generated on the surface by nitriding treatment to obtain high hardness, so that a mold having excellent wear resistance can be obtained.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited to these, and various modifications can be made based on the technical concept of the present invention.

[0024] For example, in the above embodiment, the gate-piece 4 is the mold portion forming a gate opening 33 which is connected to the space between the gate 31 and the gate 31 and the cavity 32
Although the first and the first are separated from the lower cavity blocks 52 and 52 ', they may be formed integrally with the lower cavity blocks 52 and 52'. Further, the shapes of the gate pieces 41 and 51 do not need to be limited to those in the above embodiment. Further, in the above embodiment, the multi-plunger mold having a plurality of sets of the pot 35 and the plunger 7 has been described. However, the present invention may be applied to another type of mold, for example, a production mold. A mold 6 having a runner block 27 forming a runner 36 as shown in FIG.
0 (here, the lower mold cavity block forming the cavity 32 is indicated by 52 ″, and the gate piece is indicated by 51 ′).

In the above embodiment, tool steel was used as the material (base material) before the nitriding treatment. However, any other material that can provide a sufficient hardness to the hardened layer by the nitriding treatment can be used. Stainless steel, nitrided steel, structural steel, etc. may be used.

Further, in the above embodiment, the nitriding treatment is performed by using the thermal decomposition of lime nitriding.
For example, a hardened layer may be formed on the surface by a gas nitriding method. In this case, in order to improve the wear resistance, the treatment time is lengthened, or the amount of the element contained in the base material is changed, and the thickness of the hardened layer is several tens μm to several hundred μm. It is good to be generated to the extent.

[0027]

As described above, according to the resin molding die of the present invention, after processing into a predetermined shape, nitriding is performed to obtain a hardness equivalent to that of a cemented carbide. )
The time required for processing can be reduced without lowering the abrasion resistance, and the mold can be formed at a low cost.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a mold according to a first embodiment of the present invention.

FIG. 2 is a partial plan view taken along the line [2]-[2] in FIG.

FIG. 3 is a perspective view of a gate piece according to the first embodiment of the present invention.

FIG. 4 is a front sectional view of an apparatus used when nitriding the surface of the gate piece in the mold according to the first embodiment of the present invention.

FIG. 5 is a partial plan view of a mold according to a second embodiment of the present invention.

FIG. 6 is a perspective view of a gate piece according to a second embodiment of the present invention.

FIG. 7 is a partial perspective view of a main part of a mold according to a modification of the present invention.

FIG. 8 is a perspective view of a lower mold in a conventional example.

FIG. 9 is a front sectional view of a mold in a conventional example.

FIG. 10 is a partially enlarged view of a main part in FIG. 9;

[Explanation of symbols]

1 ... upper mold, 2, 2 ', 2 "... lower mold, 5 ... resin, 7
…… Plunger, 11 …… Base block, 12 …… Upper mold cavity block, 13 …… Cul block, 21…
... Holder base, 23 ... Pot block, 31 ...
Gate, 32 … cavity, 32 a … space, 33 …
... gate opening, 35 ... pot, 40 ... mold, 41, ...
... Gate piece, 41a ... Groove, 42 ... Curing layer, 44
… Ridge, 50… mold, 51… gate piece, 5
1a Groove, 52, 52 ', 52 "Lower cavity block, 54 Protrusions, 60 Mold.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B29L 31:34

Claims (5)

[Claims] 1. A plunger for pressurizing a molding material, at least a pot in which the plunger is provided and the molding material is supplied; a cavity into which the molding material is injected to seal a semiconductor element; and the pot. In a resin molding die having a gate for guiding the molding material to the cavity from above, a portion forming a connection space between the gate and the cavity is processed into a predetermined shape, and then the connection space is formed. A resin molding die, wherein the part is subjected to a nitriding treatment. 2. The resin molding die according to claim 1, wherein the portion forming the connection space is separable. 3. The resin according to claim 1, wherein a material of the portion forming the connection space is any one of tool steel, stainless steel, nitrided steel, and structural steel. Mold for molding. 4. The resin molding die according to claim 3, wherein a depth of the hardened layer generated by the nitriding treatment is several tens μm to several hundred μm from the surface. 5. The method according to claim 1, wherein the nitriding treatment is performed on lime nitrogen (CaCN
5. The resin molding die according to claim 4, wherein the nitriding treatment utilizing the thermal decomposition reaction of ₂ ) is performed.