JPH06166064A - Degassing mechanism for resin sealing mold - Google Patents

Abstract

PURPOSE:To properly escape the residual gas in a cavity at resin sealing and make suitable resin sealing molding possible even when the thin packaging and the like of a semiconductor device is concerned. CONSTITUTION:When resin sealing is performed under the condition that a semiconductor chip 18 placed on a lead frame 16 is positioned in a cavity formed by an upper and a lower mold inserts 10 and 12, in the degassing mechanism of a resin sealing mold for escaping the gas in the cavity 14, degassing mechanisms 22 and 24, which communicate with open air, are provided at the sites of mold inserts opposite to the plane of the semiconductor chip 18 positioned in the cavity 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas releasing mechanism for a resin-sealed mold.

[0002]

2. Description of the Related Art Conventionally, in a resin-sealed mold for sealing a semiconductor chip with a resin, an exhaust port (air vent) for venting gas in a cavity is provided on upper and lower split surfaces (parting surfaces) of the mold. It was being done. That is, the air vent is provided in the resin-sealing mold in a position that is in contact with the side surface of the package in the horizontal direction with respect to the plane of the semiconductor chip and at substantially the center in the package thickness direction.

[0003]

However, when the package of a semiconductor device or the like is thinned and the ratio of the thickness of the chip and the heat dissipation plate to the total thickness of the package is increased as in the recent years, the conventional air vent has It becomes difficult to evacuate the gas properly. The situation will be described with reference to FIGS. 7 and 8. As shown in FIG. 7, when the chip is located in the central portion of the cavity 60 and the air vent 62 is provided at a position facing the gate 61, first, from both side portions where the flow resistance of the molten resin is small, FIG.
As shown in FIGS. 7A and 7B, the resin wraps around and closes the air vent 62. As a result, as shown in FIG. 7C, the gas remains in the central portion 63 of the semiconductor chip plane without being exhausted. Then, as shown in FIG. It becomes a state of being compressed by (final pressure).

FIG. 8 shows a state of resin molding of a QFP (Quad Flat Package) type semiconductor device.
In this cavity 70, air vents are formed in three directions with respect to one gate 71. First, as in the case of FIG. 7, the molten resin first wraps around the air vent 72 from the outer peripheral portion where the flow resistance of the molten resin is small. Block (FIG. 8 (A), FIG. 9 (B)). Next, the gas remains in the central portion 73 of the plane of the semiconductor chip and is in a compressed state (FIG. 8C, FIG.
(D)). This has become remarkable in recent thin packages because the gap between the upper and lower surfaces of the semiconductor chip and the inner surface of the mold cavity becomes extremely narrow, and the flow resistance of the molten resin becomes extremely high in that portion, It is a situation that cannot be dealt with only by molding conditions. Also, if the flow resistance of the resin on the surface of an insert such as a semiconductor chip or heat sink is high, or if the plane of the semiconductor chip becomes large, gas is trapped near the center of the insert in the same way as above. It will be easier.

When the gas is confined as described above and remains in the cavity, an unfilled portion remains in the package,
It becomes a state that it encloses the gas, and it may burst when soldering all at once, or it may break due to aging. In addition, defects such as forming a low-density package having pores and causing voids occur.

Therefore, an object of the present invention is to provide a resin encapsulation, which can suitably escape the gas remaining in the cavity at the time of resin encapsulation and can suitably perform resin encapsulation molding, even for a thin package of a semiconductor device or the like. It is to provide a degassing mechanism for a stop die.

[0007]

In order to achieve the above object, the present invention has the following constitution. That is, in the first structure of the gas releasing mechanism of the resin-sealed mold of the present invention, the semiconductor chip mounted on the lead frame is positioned in the cavity formed by the upper and lower mold inserts for resin sealing. At this time, in the degassing mechanism of the resin-sealed mold for degassing the gas in the cavity, degassing is performed so as to communicate with the atmosphere at the part of the mold insert facing the plane of the semiconductor chip located in the cavity. It is characterized in that a mechanism is provided.

According to a second structure corresponding to claim 2, when a semiconductor chip mounted on a lead frame is positioned in a cavity formed by upper and lower mold inserts for resin sealing, In a degassing mechanism of a resin-sealed mold for degassing, a through hole provided so as to communicate with the atmosphere is provided at a portion of the mold insert facing the plane of the semiconductor chip located in the cavity. It is characterized in that a degassing pin having an outer shape smaller than that of the through hole is fitted so as to form a minute gap with the hole.

In the degassing mechanism of the resin-sealed mold according to the above-mentioned second structure, the gas-releasing pin causes the ejector pin to move along with the operation of the ejector pin for releasing the resin-sealed semiconductor device from the cavity. The degassing mechanism can be suitably restored without damaging the semiconductor chip by being provided so as to reciprocate so as to project into the cavity slightly later than the operation of the pin. Further, a flange portion is provided on the gas vent pin, and the flange portion of the gas vent pin is located in a through hole provided in a chase holding the mold insert, and comes into contact with the flange portion to come out of the gas vent pin. By fixing the cover plate for restricting the above to the outer surface of the chase, the tip end surface of the gas vent pin can be made to preferably coincide with the inner surface of the cavity. Further, in the degassing mechanism of the resin sealing mold,
The ejector pin for releasing the resin-sealed semiconductor device from the cavity is fitted in the through hole provided in the portion of the mold insert that does not face the plane of the semiconductor chip located in the cavity, The gas can be suitably discharged from the cavity without damaging the semiconductor chip.

According to a third structure corresponding to claim 6, when a semiconductor chip mounted on a lead frame is positioned in a cavity formed by upper and lower mold inserts for resin sealing, In a gas release mechanism of a resin-sealed mold for removing gas, a porosity is provided in a through hole provided so as to communicate with the atmosphere at a portion of the mold insert facing the plane of the semiconductor chip located in the cavity. It is characterized in that a pin-shaped member formed of metal is fitted.

According to a fourth structure corresponding to claim 7, when a semiconductor chip mounted on a lead frame is positioned in a cavity formed by upper and lower mold inserts for resin sealing, In a gas release mechanism of a resin-sealed die for releasing gas, a tip portion is provided in a through hole provided so as to communicate with the atmosphere at a portion of the die insert facing a plane of the semiconductor chip located in the cavity. It is characterized in that a pin-shaped member having a gas reservoir portion is fitted in.

[0012]

According to the first structure of the gas releasing mechanism for the resin-sealing die of the present invention, even in a thin package of a semiconductor device, the gas remaining in the vicinity of the center of the cavity during resin sealing is eliminated. It is possible to suitably escape, and it is possible to suitably perform resin sealing molding. According to the second configuration, a gas vent pin having a smaller outer shape than the through hole is fitted into the through hole of the mold insert so as to form a minute gap between the through hole and the through hole.
The gas accumulated in the cavity facing the flat portion of the semiconductor chip is suitably discharged through the gap between the through hole and the gas vent pin.

Further, the pin-shaped member formed of a porous metal can positively discharge the gas in the cavity. Further, even if the pin-shaped member is positively provided with a portion for collecting gas, the gas remaining in the cavity can be suitably released so as not to adversely affect the resin molding.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an embodiment of a gas release mechanism for a resin-sealed mold according to the present invention, FIG. 2 is a cross-sectional view showing the installation state of a gas release pin, and FIG. 3 is a view showing gas on the surface of a mold insert. It is a top view which shows the positional relationship between a removal pin and an ejector pin. The embodiment of FIG. 1 shows a main part of a transfer mold, where 10 is an upper mold insert and 12 is a lower mold insert. A cavity 14 is formed by the upper and lower mold inserts, and the semiconductor chip 18 mounted on the lead frame 16 is located in the cavity 14. Then, the molten resin in the pot is pushed into the cavity 16 via the gate 20 by the plunger, and the resin-sealed semiconductor device is molded.

Reference numeral 22 denotes a through hole, which is the cavity 16
It is provided so as to communicate with the atmosphere at the upper and lower mold inserts 10, 12 facing the front and back surfaces of the plane of the semiconductor chip 18 located therein. Then, a gas vent pin 24 having an outer shape smaller than that of the through hole 22 is fitted so as to form a minute gap with the through hole 22.
It should be noted that the clearance between the through hole 22 and the gas vent pin 24 is small enough to allow the gas vent pin to slide freely through the through hole because the high pressure air flows therethrough. Further, as shown in FIG. 3, the through hole 22 into which the gas release pin 24 is fitted is provided at a portion of the mold insert corresponding to the substantially central portion of the cavity surface where the gas is likely to remain. The residual air is suitably discharged through the slight clearance between the through hole 22 and the gas vent pin 24.

A collar portion 2 is provided in the middle of the gas vent pin 24.
6 is provided, and this collar portion 26 is located in a through hole 30 of a chase provided in each chase 28, 29 holding the upper and lower mold inserts 10, 12. Then, the tip end surface of the gas vent pin 24 becomes flush with the inner surface of the cavity 16, and the gas vent pin 24 makes the chase 2
A cover plate 32 is fixed to the outer surface of each chase 28, 29 so as to come into contact with the flange portion 26 of the gas vent pin so as to prevent the chase 28, 29 from coming off. In Figure 2,
The cover plate 32 is chase 28 by bolts 35.
Shows a state in which it is suitably fixed. 2 is a cross-sectional view showing a part of the AA cross section of the embodiment shown in FIG. Also,
The rear portion of the gas vent pin 24 is inserted into the through hole 33 of the cover plate which is penetrated by the cover plate 32, and the rear end portion of the gas vent pin 24 is normally urged by the spring 40. It projects from the outer surface of the cover plate 32.

Therefore, when the upper and lower molds are relatively opened, the gas vent pin 24 is moved by the operation of the ejector pin 34 for releasing the resin-sealed semiconductor device from the cavity 16. It projects into the cavity 16 slightly later than the operation of 34. That is, the ejector pin plate 36 that holds and presses the ejector pin 34 together with the retainer plate 38 is brought into contact with the rear end surface of the gas vent pin 24, and the pressing force of the ejector pin plate 36 resists the urging force of the spring 40. And is pressed, and the tip end portion is projected into the cavity 16. At this time, the rear end surface of the gas vent pin 24 and the ejector pin plate 36
The degassing pin 24 operates slightly later than the ejector pin 34 because there is a gap between and. As a result, the semiconductor chip 18 is prevented from exerting a shocking pressing force on the package by the operation of the gas vent pin 24.
There is no fear of damaging. The ejector pin 34 is
Is fitted into a through hole provided in a portion of the mold inserts 10 and 12 that does not face the plane of the semiconductor chip 18 located in the cavity so as not to damage the semiconductor chip 18.

When the ejector pin 34 is pulled into the die, the gas vent pin 24 is also pulled into the die along with its operation. By the reciprocating movement of the gas vent pin 24, the periphery of the gas vent pin 24 and the through hole 22
It is possible to remove the resin that has flowed into the gap between and, and to suitably return the gas venting mechanism to the original state for the next resin sealing. It should be noted that the gas vent pin 24 exerts an ejecting force only when the resin-molded package is released from the mold and is deflected beyond the control range at the center thereof to prevent abnormal deflection of the package. It also has a function to prevent it.

Further, the tip end surface of the gas vent pin 24 is positioned so as to be flush with the inner surface of the cavity so that only a very slight trace is left on the surface of the package. By the way, like the gas vent pin 24,
As shown in FIG. 1, the ejector pin 34 slidably fitted in the through hole of the mold insert has its tip slightly (about 0.1 mm) projected from the inner surface of the cavity during resin molding. On the surface, the traces remain in the form of steps. The reason is ejector pin 3
This is because it is difficult to make the front end surface of No. 4 the same as the inner surface of the cavity with high precision, and it is not desirable to form a convex portion on the outer surface of the package during mounting or the like. That is, it is difficult for the ejector pin 34 to accurately define the depth of the fitting mounting hole and the distance between the ejector pin plate 36 and the chase 28. Further, the ejector pin 34 includes the retainer plate 38 and the ejector pin plate 36.
Holding section and chase 2 having different temperature settings from the holding section
8 and the mold insert 10.
As a result, the temperature distribution of the ejector pin 34 is biased, and the ejector pin 34 is distorted. further,
The ejector pin 34 is deformed under the influence of bending by an ejecting rod (not shown). For this reason, it is difficult to make the tip end surface of the ejector pin 34 the same as the inner surface of the cavity, and there is no choice but to project it inside the cavity.

On the other hand, in the gas vent pin 24 according to the present invention, the flange portion 26 of the gas vent pin 24 is fitted in the through hole 22 penetrating the chase 28, 30 and the position thereof is regulated by the cover plate 32. It Therefore, in order for the tip surface of the gas vent pin 24 to be flush with the inner surface of the cavity, the mold inserts 10, 12 and the chase 2 are
It suffices that the thicknesses of 8 and 29 and the dimensions of the gas vent pin 24 are matched, and the tip end surface of the gas vent pin 24 and the inner surface of the cavity can be accurately and easily positioned on the same plane. As a result, according to the structure of the gas vent pin 24, the pin tip surface can be aligned with the inner surface of the cavity with an accuracy of 5 microns or less, and only a slight streak is formed on the surface of the package. Is not deteriorated.

FIG. 4 is an explanatory view showing another embodiment of the present invention, in which the semiconductor chip 18 located in the cavity 16 is shown.
A pin-shaped member 42 formed of a porous metal is fitted into a through hole 22 provided so as to communicate with the atmosphere at a portion of the mold insert 10 that faces the plane. As a result, the gas remaining after being caught up at the position corresponding to the center of the semiconductor chip 18 can be suitably discharged. Further, it is possible to provide a discharging device 45 and positively discharge. The resin that has entered and adhered to the porous metal can be cleaned by back-injecting air, brushing, or the like.

Further, as shown in FIG. 5A, the pin-shaped member 50 positively provided with the gas reservoir 52 can be reciprocated in the through hole of the mold insert corresponding to the center of the cavity 16 of the upper mold. Then, as shown in FIG. 5B, the pin-shaped member 5 is inserted.
0 may be pulled up in the final step of resin filling. As a result, the residual gas is reliably contained in the gas reservoir 52 formed in a concave shape at the tip of the pin-shaped member 50, and the package shape does not protrude beyond the package surface and is resin-sealed. There is no possibility of damaging the semiconductor chip 18 by applying a pressing force.

Further, as shown in FIG.
Vertical burrs with eject pins are strictly prohibited, but this may be used. That is, the tip end of the pin-shaped member 54 is a stepped portion 56 having a diameter smaller than that of the through hole 22, and the gas is positively guided between the stepped portion 56 and the through hole 22 to perform resin molding. Is preferably performed. At this time,
Vertical burrs occur in the direction perpendicular to the chip plane.
The molded product can be easily removed as an unnecessary portion in another step after taking out the mold. Further, if the pin-shaped member 54 is provided so as to be movable up and down, and the pin-shaped member 54 is projected when the molded product is released from the mold as shown in FIG. The resin can be suitably scraped out, and there is no possibility that the resin remains in the through holes 22 of the mold insert 10 and the pin-shaped member 54 malfunctions.

It is needless to say that the gas venting mechanism of the above embodiments may be set in both upper and lower dies, or only in one of them, if necessary. For example, in the case of the embodiment shown in FIG. 1 above, a gas venting mechanism is provided on both sides of the upper and lower molds in order to seal the entire chip. However, in the embodiment shown in FIGS. Since the one side is exposed, the degassing mechanism is provided only in the upper die. Further, in the gas venting mechanism of the above embodiment, especially in the embodiment as shown in FIG. 1, the clearance between the through hole 22 and the gas vent pin 24 is set to such an extent that gas is discharged but resin does not enter. Therefore, the amount of gas discharged is limited. Therefore, it goes without saying that the degassing mechanism according to the present invention may be used in combination with the conventional side vent as shown in FIG. 7 or 8. Although various preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention. That is.

[0025]

According to the degassing mechanism of the resin encapsulating mold of the present invention, even in a thin package of a semiconductor device, the gas remaining in the cavity during resin encapsulation can be suitably escaped, and resin encapsulation can be performed. It has a remarkable effect that molding can be suitably performed. As a result, it is possible to dramatically expand the range of possible resin encapsulation molding for packages with a high semiconductor chip area occupancy, ultra-thin packages such as tape carrier types, and packages with heat sinks. Play.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a gas release mechanism for a resin-sealed mold according to the present invention.

FIG. 2 is a cross-sectional view showing an installed state of the gas vent pin of FIG.

3 is a plan view showing the surface of the mold insert of FIG. 1. FIG.

FIG. 4 is a sectional view showing another embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating another embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating another embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating a resin sealing state of a conventional semiconductor chip.

FIG. 8 is an explanatory diagram illustrating a resin sealing state of a semiconductor chip according to a conventional QFP.

[Explanation of symbols]

 10 Upper Mold Insert 12 Lower Mold Insert 14 Cavity 16 Lead Frame 18 Semiconductor Chip 20 Gate 22 Through Hole 24 Gas Release Pin 26 Collar 28 Upper Mold Chase 29 Lower Mold Chase 30 Chase Through Hole 32 Cover Plate 34 Ejector Pin 36 Ejector Pin Plate 38 Retainer plate 40 Spring 42 Pin-shaped member 50 Pin-shaped member 52 Gas reservoir 54 Pin-shaped member 56 Stepped portion

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // B29K 105: 20 B29L 31:34 4F

Claims (7)

[Claims] 1. A gas of a resin-sealed mold for removing a gas from the cavity when a semiconductor chip mounted on a lead frame is positioned in a cavity formed by upper and lower mold inserts for resin sealing. In the venting mechanism, a gas venting mechanism is provided at a portion of the die insert facing the plane of the semiconductor chip located in the cavity so as to communicate with the atmosphere. Removal mechanism. 2. A gas of a resin-sealed mold for removing a gas in the cavity when a semiconductor chip mounted on a lead frame is positioned in a cavity formed by upper and lower mold inserts for resin sealing. In the punching mechanism, a minute gap is formed between the through hole provided in the cavity of the die insert facing the plane of the semiconductor chip located in the cavity so as to communicate with the atmosphere. As described above, the degassing mechanism of the resin-sealed mold is characterized in that a degassing pin having an outer shape smaller than that of the through hole is fitted therein. 3. The reciprocating motion of the gas releasing pin, so that the gas releasing pin projects into the cavity slightly later than the operation of the ejector pin, as the ejector pin releases the resin-sealed semiconductor device from the cavity. The degassing mechanism for a resin-sealed mold according to claim 2, which is provided freely. 4. A degassing pin is provided with a flange, and the degassing pin has a flanged portion located in a through hole provided in a chase for holding a mold insert, and comes into contact with the flanged portion to release the gas. The degassing mechanism for a resin-sealed mold according to claim 2 or 3, wherein a cover plate that restricts the pin from coming out is fixed to the outer surface of the chase. 5. An ejector pin for releasing a resin-sealed semiconductor device from a cavity is fitted in a through hole provided in a portion of a mold insert that does not face the plane of the semiconductor chip located in the cavity. The degassing mechanism for a resin-sealed mold according to claim 1, 2, 3, or 4. 6. A gas of a resin-sealed mold for removing a gas from the cavity when a semiconductor chip mounted on a lead frame is positioned in a cavity formed by upper and lower mold inserts for resin sealing. In the extraction mechanism, a pin-shaped member formed of a porous metal is inserted into a through hole provided at a portion of the mold insert facing the plane of the semiconductor chip located in the cavity so as to communicate with the atmosphere. What has been done is a gas release mechanism for a resin-sealed mold. 7. A gas of a resin-sealed mold for removing a gas in the cavity when a semiconductor chip mounted on a lead frame is positioned in a cavity formed by upper and lower mold inserts for resin sealing. In the extraction mechanism, a pin-like shape having a gas reservoir formed at its tip end in a through-hole provided at a portion of the mold insert facing the plane of the semiconductor chip located in the cavity so as to communicate with the atmosphere. A degassing mechanism for a resin-sealed mold, characterized in that a member is fitted therein.