JPH081708A - Mold and molding equipment in which it is used - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the wear resistance and releasability of the mold. [Structure] The tungsten carbide coating 3 is deposited on the surfaces of the cavity recesses 15 and 25, the sub-runner 26, the gate 27, and the air vent 28 of the molding die 2. The ejector pin is omitted in the molding apparatus 1 using this molding die 2. [Effect] Since the tungsten carbide coating has high wear resistance, the durability of the molding die becomes high. Further, since the mold release property of the molding die is enhanced by the deposition of the tungsten carbide coating, the mold product is easily released from the cavity and the adhesion of the molding material to the surface is suppressed. By facilitating the release of the molded product from the cavity, it becomes possible to release the molded product from the cavity without pushing up the ejector pin, so that the ejector pin can be omitted from the molding device. it can. By omitting the ejector pins, the structure of the molding die and the molding apparatus as a whole is simplified, and various defects due to defective sliding of the ejector pins are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding technique, and more particularly, to a technique for improving the wear resistance and mold releasability of a molding die.
The present invention relates to a technique effectively used for molding a resin sealing body of a resin sealing type package in a manufacturing process of a semiconductor device.

[0002]

2. Description of the Related Art Generally, a transfer molding apparatus for molding a resin encapsulant of a resin encapsulation type package in a semiconductor device manufacturing process includes an upper die and a lower die which are clamped to each other. After the wire-bonded lead frame is sandwiched between the mating surfaces of the upper mold and the lower mold, resin as a molding material (hereinafter,
Called resin. ) Is filled in the cavity through a pot, a runner and a gate, and a resin encapsulant for resin encapsulating the semiconductor pellet, the inner leads and the wire is resin-molded by the cavity.
The resin sealing body molded by the cavity is separated from the cavity by pushing up the ejector pin slidably supported by the molding die so as to advance and retreat with respect to the cavity. .

In a conventional transfer molding apparatus of this type, a molding die formed using cold die steel (SKD) and having a hard chrome plated surface is used. .

Incidentally, examples in which such a transfer molding apparatus is described are disclosed in JP-A-2-44739 and JP-A-5-285975.

[0005]

However, in the conventional mold having the surface treated with hard chrome plating, the wear resistance and the releasability are insufficient, and the resin adheres to the air vent. It has been clarified by the present inventor that there is a problem that defective filling of the cavity occurs.

[0006] A first object of the present invention is to provide a molding die capable of enhancing wear resistance and mold releasability.

Further, in the above-mentioned conventional transfer molding apparatus, since the resin sealing body as a molded product is configured to be released from the cavity by pushing up the ejector pin, the structure of the molding die and the molding The present inventor has revealed that not only the structure of the entire device becomes extremely complicated, but also various defects occur due to defective sliding of the ejector pin.

A second object of the present invention is to provide a molding apparatus capable of avoiding the occurrence of defects due to defective sliding of ejector pins.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0010]

The typical ones of the inventions disclosed in the present application will be outlined below.

That is, at least the surface of the cavity of the molding die is coated with a coating made of tungsten carbide.

Further, the ejector pin is omitted in the molding apparatus using the molding die in which the coating film made of tungsten carbide is applied to at least the surface of the cavity.

[0013]

In the above-mentioned means, since the tungsten carbide coating has high wear resistance, the durability of the molding die is high. Further, since the mold release property of the molding die is enhanced by the deposition of the tungsten carbide coating, the mold product is easily released from the cavity and the adhesion of the molding material to the surface is suppressed.

Further, since it becomes easy to release the molded product from the cavity, the molded product can be released from the cavity without pushing up the ejector pin. Can be omitted. By omitting the ejector pin from the molding device, not only the structure of the molding die and the structure of the entire molding device are simplified, but also various defects due to defective sliding of the ejector pin are prevented.

[0015]

1 is an enlarged partial front sectional view showing a transfer molding apparatus according to an embodiment of the present invention. FIG. 2 is a partially omitted front sectional view for explaining the operation. FIG.
FIG. 3 is a partial perspective view showing a lower die of a molding die used therein. FIG. 4 shows the molded resin body after molding,
(A) is a partially omitted plan view with part omitted, and (b) is a front sectional view. FIG. 5 and subsequent figures are graphs for explaining the operation.

In this embodiment, the molding apparatus according to the present invention is configured as a transfer molding apparatus 1 for molding a resin sealing body of a resin sealing package of a semiconductor device. The transfer molding apparatus 1 includes a molding die 2 including an upper die 10 and a lower die 20. The upper die 10 and the lower die 20 are attached to the upper die mounting unit 30 and the lower die mounting unit 40, respectively, and are configured to be clamped to each other by a die opening / closing cylinder device (not shown). The upper mold mounting unit 30 and the lower mold mounting unit 40 include mold plates 31, 41, outer frames 32, 42,
It is composed of spacer blocks 33 and 43.
A plurality of heaters 34 and 44 are laid inside the template plates 31 and 41, respectively.
The template plates 31, 41 are heated by 44.

The upper mold 10 is a center block 11 at the center.
And a pair of cavity blocks 12, 12 arranged on both sides thereof. The lower mold 20 is the upper mold 10.
Similarly, the center block 21 in the center and the pair of cavity blocks 22, 2 arranged on both sides of the center block 21.
2 is provided. The pair of cavity blocks 12 and 12 and the pair of cavity blocks 22 and 22 are formed symmetrically.

In the center block 11 of the upper mold 10, a pot 13 into which a molding material (hereinafter referred to as a tablet) made by compacting powder resin is put is opened vertically, and the pot 13 is molded. A plunger 14 for pressure-feeding a liquid resin (resin) as a material is inserted so as to be movable back and forth. On the other hand, on the upper surface of the center block 21 of the lower mold 20, a cull 23 is sunk in a circular shallow hole shape at a position corresponding to the pot 13.
A runner (hereinafter, referred to as a main runner) 24 is submerged on the upper surface of the center block 21 of the lower mold 20 so as to communicate with the cull 23 at one end.

On the mating surface of each cavity block 12 of the upper mold 10, a plurality of upper mold cavity recesses 15 are regularly arranged and are respectively recessed into a square shallow hole shape having a constant depth. A plurality of lower mold cavity recesses 25 are arranged on the mating surface of each cavity block 22 of the lower mold 20 so as to face each upper mold cavity recess 15 and are aligned with the upper mold cavity recesses 15. It is sunk in the shape of a square shallow hole with a certain depth. Then, the upper mold cavity concave portion 15 and the lower mold cavity concave portion 25 cooperate with each other in a state of being matched with each other to individually form a cavity 16 having a square shape and a low airtight chamber shape. Has been done.

Further, a plurality of sub-runners 26 are provided at one long side portion on the upper surface of the lower mold cavity block 22 at equal intervals in the longitudinal direction. One end of each sub-runner 26 is fluidly connected to each main runner 24 of the lower die center block 21, and the other end of each sub-runner 26 is in a predetermined corner portion of each lower die cavity recess 25. Each is fluidly connected. And each lower mold cavity recess 2
Gates 27 are opened at the connection portions of the sub-runner 26 in FIG. 5, and the gate 27 is configured so that the resin from the sub-runner 26 can be effectively filled in the cavity 16.

Further, the gate 27 of each lower mold cavity recess 25 on the upper surface of the lower mold cavity block 22.
Air vents 28 are recessed so as to extend in a diagonal direction at three corners except for the corners in which the air vents are formed. The air vent 28 can effectively discharge the air from the cavity 16, but the air vent 28 is configured to prevent the discharge of the resin as much as possible.

In this embodiment, the lower surface of the upper mold cavity block 12 and the upper surface of the lower mold cavity block 22 are coated with ditungsten monocarbide (W ₂ C) (hereinafter referred to as tungsten carbide coating) 3. Are generally covered. That is, the tungsten carbide coating 3
Is the upper mold cavity recess 15 and the lower mold cavity recess 2
5, sub-runner 26, gate 27 and air vent 2
Each surface of No. 8 is in a coated state. The hardness of this tungsten carbide coating 3 is 1
It is 500-2500 micro Vickers hardness. The tungsten carbide coating 3 is formed by the low temperature CVD method.
It has a thickness of about 10 μm and is uniformly applied.

The upper mold 10 and the lower mold 20 having the above-mentioned structure are attached to the upper and lower mold mounting units 30 and 40.
Embedded in the joint surfaces of the template plates 31 and 41 in FIG. In the present embodiment, the upper mold mounting unit 30 and the lower mold mounting unit 40
Has no ejector mechanism attached. Therefore, the ejector pin insertion hole is not formed in each block of the upper mold 10 and the lower mold 20. As a result, the structure of the transfer molding apparatus 1 is extremely simple.

Next, the operation will be described. Here, in this transfer molding apparatus, a work 50 for outsert molding a resin sealing body is used. The work 50 includes a multiple lead frame 51 in which a plurality of unit lead frames 52 are arranged.
The pellets 57 are respectively bonded to the tabs 53 of the
The wire 58 is bridged between the inner lead 54 and the inner lead 54. Further, each outer lead 55 is integrally connected to each inner lead 54, and a dam 56 is bridged between adjacent outer leads 55, 55.

When the transfer molding apparatus 1 having the above-mentioned configuration is used to mold the resin sealing body 5 on the work 50, the work 50 is placed on the mating surface of the lower mold 20 and the pellet 57 which is an object to be sealed. , The inner leads 54 and the bonding wires 58 are positioned so as to be housed in the lower mold cavity recess 25. Subsequently, the upper mold 10 and the lower mold 20 are clamped by a mold opening / closing cylinder device (not shown). With this mold clamping, the cavity 16 is formed by the upper mold cavity concave portion 15 and the lower mold cavity concave portion 25, and the work 50 is fixed to the upper mold cavity 10.
And the lower mold 20.

Upper mold 10 and lower mold 2 with a predetermined mold clamping force.
When 0 is clamped, a tablet (not shown) is placed in the pot 13 of the upper center block 11. The charged tablets are heated and melted by the heaters 34 and 44 to become the liquid resin 4. In the molten state, the resin 4 is pushed out from the cull 23 to the main runner 24 of the center block 21 by each plunger 14 that is lowered by a transfer cylinder device (not shown). The resin 4 thus pushed out is pressure-fed through the sub-runner 26 of each lower mold cavity block 22, and is filled into each cavity 16 from the gate 27. Each cavity 1
When the resin 4 filled in 6 is further heated, it cures to form the resin encapsulant 5 shown in FIG.

When the resin sealing body 5 is molded, the upper mold 10 and the lower mold 20 are opened by the mold clamping cylinder device. At this time, since the work 50 is separated from the upper mold 10 and the lower mold 20, the resin sealing bodies 5 outsert-molded into the work 50 are separated from the cavity recesses 15 and 25, respectively. It becomes the state shown in. The work 50 released from the molding die 2 is conveyed from the transfer molding apparatus 1 to the next step. After that, by repeating the above operation, the resin sealing body 5 is molded for each work 1.

By the way, resin 4 as a resin molding material
In addition to epoxy resin, curing agent, release agent, etc., a filler (aggregate) made of oxide such as silica is mixed. Due to the nature of the aggregate, this filler (not shown) is extremely hard, and the surfaces of the runner, gate and cavity through which the resin 4 flows will be worn in a short period of time.

However, in this embodiment, the tungsten carbide coating 3 is formed on the upper surface of the upper mold cavity block 12 and the lower surface of the lower mold cavity block 22 by the low pressure CVD.
By being applied by the method, the sub-runner 26,
Since the surfaces of the gate 27, the air vent 28 and the cavity 16 are covered with the tungsten carbide coating 3 having excellent wear resistance, it is necessary to prevent these surfaces from being worn in a short period of time by the flow of the resin 3. You can

That is, as understood from the graph shown in FIG. 5A, the wear resistance of the tungsten carbide (W ₂ C) material is much higher than that of the conventional hard chromium plating film. FIG. 5A is a graph comparing the wear resistance of each material, in which the vertical axis indicates the wear amount of the disk (× 10 ^−10).
mm ³ / g · mm) and each material is plotted on the horizontal axis. In addition, in FIG. 5A, the amount of disc wear of SKD11 (H) is much larger than that of other materials.
(× 10 ⁻¹⁰ mm ³ / g · mm). Incidentally, this graph was created based on the data obtained by the experiment shown in FIG. 5 (b).

A release agent is mixed in the resin 4. However, since the releasing performance of the release agent is limited, the resin 4 adheres to the surfaces of the cavity 16 and the air vent 28 as residual dust while the molding operation described above is repeated. Remaining waste of resin 4 is cavity 16
If it adheres to the surface of the resin encapsulant, the resin encapsulant 5 will be defective in shape and demolded. Further, when the residual debris of the resin 4 adheres to the air vent 28, the air vent 28 is clogged, so that the air in the cavity 16 is not satisfactorily exhausted, resulting in insufficient filling of the resin 4 into the cavity 16 or internal Voids are generated, causing a defective shape of the resin sealing body 5 and the like.

However, in this embodiment, the tungsten carbide coating 3 is applied to the surfaces of the cavity 16 and the air vent 28, so that the mold releasing performance of the surfaces of the cavity 16 and the air vent 28 itself is improved. Therefore, the remaining debris of the resin 4 is extremely effectively prevented from adhering to the cavity 16 and the air vent 28. That is, as shown in FIG. 6 (a), the mold release performance of the tungsten carbide (W ₂ C) material is extremely higher than that of the hard chrome plating film that has been conventionally adhered to the mold, so that the cavity The phenomenon that the resin 4 adheres to the air vent 16 and the air vent 28 is very effectively prevented. FIG. 6A is a graph comparing the mold release performance with respect to polycarbonate, in which the mold release load (N) of the polycarbonate is plotted on the vertical axis and the respective materials are plotted on the horizontal axis. By the way, this graph was created based on the data obtained by the experiment shown in FIG. 6 (b).

FIG. 7 is a graph showing the air vent resin attachment rate for each coating on the air vent surface.
The vertical axis shows the resin adhesion rate (%), and the horizontal axis shows the number of shots. In FIG. 7, broken line W ₂ C is the tungsten carbide coating of this embodiment, and broken line HCr is the conventional hard chrome plating coating. As is clear from the comparison between the two broken lines, in the case of the present embodiment in which the tungsten carbide coating was applied, the resin adhered to the air vent 28 as compared with the conventional case in which the hard chromium plating film was applied. Rate is reduced.

According to the above embodiment, the following effects can be obtained. (1) Sub-runner in cavity block,
By covering the surface of the gate, air vent and cavity recess with a tungsten carbide coating having excellent wear resistance, it is possible to prevent these surfaces from being worn in a short period of time by the flow of the resin.
The life of the molding die can be extended.

(2) Since the surface of the cavity and the air vent are coated with a tungsten carbide coating having excellent mold releasing performance, the mold releasing performance of the surface of the cavity and the air vent itself can be enhanced. It is possible to very effectively prevent the residue of resin from adhering to the air vent.

(3) The cleaning frequency of the molding die can be reduced by the above (2), and the operating efficiency of the molding apparatus can be increased in combination with the above (1).
The productivity of the molding process can be improved.

(4) By preventing the residual resin debris from adhering to the cavity and the air vent, the resin encapsulant can be prevented from being defective in shape and releasing due to adhesion of the residual resin debris to the surface of the cavity. It is possible to prevent the occurrence of such problems, and it is also possible to prevent insufficient filling of the resin cavity into the cavity due to clogging of the air vent and the occurrence of internal voids. Can be prevented, and the quality and reliability of the molded product by the molding die can be improved.

(5) Since the ejector pin can be omitted by improving the mold release performance of the molding die itself, the structure of the molding die and the structure of the entire molding apparatus can be simplified and the ejector pin It is possible to prevent occurrence of various defects due to defective sliding, and improve the quality and reliability of the molded product by the molding die and the molding device. By the way, in the conventional case where the ejector pin is inserted into the cavity recess and the molded product is pushed up from the cavity recess, the resin filled in the cavity adheres to the ejector pin insertion hole, so the ejector pin slides poorly. Is likely to occur. If the ejector pin slides badly, it will not only be impossible to release the mold, but also
Since the product-to-product variations in the depth position of the ejector pin with respect to the insertion hole occur, the traces of the ejector pin become uneven, resulting in a defective appearance of the molded product. According to the present embodiment in which the ejector pin is omitted, it is possible to prevent such a defect from occurring.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the tungsten carbide coating is not limited to being entirely deposited on the surface of the cavity block, but may be deposited at least on the surface of the cavity. But,
The tungsten carbide coating is preferably applied to the surfaces of the cavities, runners, gates and air vents.
Further, the tungsten carbide coating is not limited to being deposited on the surface of the cavity block, but is desirably deposited on the surfaces of the pot, cull and main runner of the center block.

The tungsten carbide coating is not limited to being formed using ditungsten monocarbide (W ₂ C), but may be formed using monotungsten monocarbide (WC).

In the above embodiment, the case where the ejector pin is omitted has been described, but it goes without saying that the ejector pin may be used.

In the above description, the case where the invention made by the present inventor is mainly applied to the transfer molding apparatus for molding the resin encapsulation body of the resin encapsulation package in the semiconductor device which is the background field of application has been described. However, it can be applied to general molding apparatuses for molding other molded products.

[0044]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

By coating the surfaces of the cavities with the tungsten carbide coating, it is possible to prevent these surfaces from being abraded in a short period of time by the flow of the resin, so that the life of the molding die can be extended. ,
Further, since the mold release performance of the cavity surface itself can be enhanced, it is possible to effectively prevent the residual resin residue from adhering to the cavity and reduce the frequency of cleaning the mold. As a result, the operating efficiency of the molding apparatus can be increased, and the productivity of the molding process can be improved. In addition, since it is possible to prevent the occurrence of defective shapes of the molded product, it is possible to improve the quality and reliability of the molded product by the molding die.

By covering the surface of the cavity with a tungsten carbide coating to improve the mold release performance of the mold itself, the ejector pin can be omitted, so that the structure of the mold and the structure of the entire molding apparatus can be simplified. In addition, it is possible to prevent the occurrence of various defects due to defective sliding of the ejector pin, and improve the quality and reliability of the molded product by the molding die and the molding device.

[Brief description of drawings]

FIG. 1 is an enlarged partial front sectional view showing a transfer molding apparatus according to an embodiment of the present invention.

FIG. 2 is a partially omitted front sectional view thereof.

FIG. 3 is a partial perspective view showing a lower die of a molding die used therein.

4A and 4B show a molded resin body after molding, in which FIG. 4A is a partially cutaway plan view and FIG. 4B is a front sectional view.

5A is a graph comparing the wear resistance of each material, and FIG. 5B is a schematic diagram showing the experimental conditions.

FIG. 6A is a graph comparing the release performance of each material, and FIG. 6B is a schematic diagram showing the experimental conditions.

FIG. 7 is a graph showing the air vent resin adhesion rate for each coating on the air vent surface.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transfer molding apparatus (molding apparatus), 2 ... Mold, 3 ... Tungsten carbide coating, 4 ... Resin, 5 ... Resin sealing body, 10 ... Upper mold, 11 ... Center block, 12 ...
Cavity block, 13 ... Pot, 14 ... Plunger, 15 ... Upper mold cavity recess, 16 ... Cavity, 20 ... Lower mold, 21 ... Center block, 22 ... Cavity block, 23 ... Cull, 24 ... Main runner, 25 ... Lower mold cavity recess, 26 ... Sub-runner, 27 ... Gate, 28 ... Air vent, 30 ... Upper mold mounting unit, 40 ... Lower mold mounting unit, 31, 41 ... Mold plate, 32, 42 ... Outer frame, 33 , 43 ... Spacer block, 34, 44 ... Heater, 50 ... Work (semi-assembly of semiconductor device), 51 ... Multiple lead frame, 52 ... Unit lead frame, 53 ... Tab, 54 ... Inner lead, 5
5 ... Outer lead, 56 ... Dam, 57 ... Pellet, 58
... bonding wire.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B29L 31:34

Claims (3)

[Claims] 1. A molding die for injecting a molding material into a cavity to mold a molded article, characterized in that at least a surface of the cavity is coated with a coating film made of tungsten carbide. 2. The tungsten carbide coating is a cavity,
The molding die according to claim 1, wherein the molding die is adhered to each surface of the air vent, the gate, and the runner. 3. A molding apparatus in which the molding die according to claim 1 is used, wherein an ejector pin is omitted.