JPH09262876A - Molding method, molding method of package for semiconductor integrated circuit device and molding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent crack from developing in a molding body at mold releasing by a method wherein the concentration of stress to the specified part of the molding body at mold releasing is relaxed by separating the molding body from a mold with compressed air. SOLUTION: By retaining a mold 1 at the predetermined curing temperature, the resin in the mold 1 is cured. A bottom mold 1A is lowered under the condition that a holding-down rod 11 is interlocked with the movement of the bottom mold 1A. Since a semiconductor package 3 is pushed with the holding-down rod 11, which is acted so as to bond onto the bottom mold 1A, and does not float from the bottom mold 1A, the semiconductor package is easily released from a top mold 1B. After the releasing of the top mold 1B, a piston rod 4 is lowered. Thus, the flow path 2 of the compressed air and a supply path are communicatingly connected to each other. Under the state just mentioned above, by opening a valve of a high pressure gas cylinder or the like, the compressed air, the pressure of which is adjusted to the predetermined pressure through a pressure reducing valve, is fed to the supplying path. The air, which is fed to the supply path and the pressure of which is reduced, flows in a flow path 2, which is opened through the lowering of the piston rod 4, resulting in applying the upward force to the semiconductor package 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding technique using a mold and a mold releasing technique from a molding die, for example, a technique useful when applied to the manufacture of a package for a semiconductor integrated circuit device.

[0002]

2. Description of the Related Art In a semiconductor integrated circuit device, a semiconductor chip (die) is bonded onto a die frame (island) with a paste, the semiconductor chip and the lead frame are connected by wires, and the assembly thus obtained. It is configured by molding around. The molding process is
The above assembly is interposed in a molding die in which the upper die and the lower die are combined, and more specifically, the lead frame is sandwiched between the upper die and the lower die, and the resin is poured into the molding die. After curing, release is performed. FIG. 9 is a diagram showing a state of mold release. In this mold release step, a semiconductor package (molded body) 3 enclosing the assembly, a lower mold 1A, and an upper mold 1B.
Since they are weakly adhered to each other, the metal pins 10 and 11 that move up and down independently of the lower mold 1A and the upper mold 1B are used. The mold release is first performed from the upper mold 1B. At this time, since the lower mold 1A is present, the upper mold 1 is lightly pressed by the pin 11 while pressing the molded product.
If B is raised, the mold can be easily released. On the other hand, in the case of releasing the lower die 1A, the upper die 1B cannot be pressed because the upper die 1B has already been separated. Therefore, the lower die 1A is pushed up by the pin (push-up pin) 10. The molded body 3 is separated from.

[0003]

However, in the above-mentioned prior art, since the upper surface side of the molded body 3 is free at the time of releasing the lower mold 1A, the pin 10 is pushed up locally to the molded body 3. Great power is added. Therefore, if the hardness of the molded body 3 is not sufficiently high, cracks may occur in the molded body. In order to avoid this, it is necessary to lengthen the curing time to sufficiently cure the resin in the mold 1.
There is a problem of low throughput.

Further, in the peripheral portion of the semiconductor chip 51,
The interface between the island 5 and the mold resin may be peeled off due to a large stress applied to the package at the time of releasing, and the peeled portion may become a starting point of the package crack.

In order to further improve the releasability and reduce the stress applied to the package as much as possible, a minute amount of a releasing agent composed of a wax component is added to the resin. Further, by keeping the temperature of the molding die 1 at a high temperature (about 170 to 185 ° C.) when the resin is cured, the curing time is shortened.
However, if the amount of the release agent added is increased or the mold temperature at the time of curing is increased, the adhesive strength at the interface between the cured resin and the island 5 becomes weak and peeling easily occurs.

The present invention has been made in view of the above circumstances, and shortens the curing time of the molding material (the time from the injection of the molding material to the release), and at the same time, the molded body is cracked during the release. It is an object of the present invention to provide a molding technique capable of preventing the occurrence of such a phenomenon and thereby improving the throughput and the yield.

[0007]

In order to achieve the above-mentioned object, the molding method of the present invention is such that the mold is released from one mold and then the other mold and the mold are separated from each other. Compressed air is introduced. In this case, as a molded body,
For example, it corresponds to a semiconductor integrated circuit device package obtained by molding a semiconductor chip provided on a frame.

Further, the molding apparatus of the present invention comprises a mold divided into at least one mold and the other mold,
In a mold for filling a molding material through a semiconductor chip supported on a frame and releasing the package for the semiconductor integrated circuit device made of the molding material after curing the molding material, the molding surface of the other mold And at least one flow path through which compressed air flows, a compressed air supply means for supplying compressed air into the flow path, and an opening / closing means capable of opening and closing the opening of the flow path, The opening / closing means closes the opening of the flow path when the molding material is filled in the molding die, and closes the opening when the package made of the cured molding material is released from the other mold. It is characterized in that it is configured so that it opens and the flow path communicates with the molding surface of the other mold.

Further, in the molding apparatus of the present invention, instead of the opening / closing means, there is provided a closing means which is provided so as to close the opening of the flow path, and which is made of a material that does not allow the molding material to pass but allows gas to pass therethrough. You may use.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as a preferred example to which the present invention is applied, a case of manufacturing a package for a semiconductor integrated circuit device (hereinafter referred to as a semiconductor package) in which a semiconductor chip is sealed with a resin will be described. A description will be given based on FIG.

FIG. 1 shows an example of a semiconductor package molding apparatus. In this molding apparatus, a compressed air flow path 2 is provided in a lower mold 1A of a molding mold 1 including an upper mold 1B which is one mold and a lower mold 1A which is the other mold. High pressure gas such as compressed air is passed through the lower mold 1 through
The semiconductor package 3 is separated from the lower mold 1A by being introduced between A and the semiconductor package 3 which is a molded body.

Inside the flow path 2 of the lower mold 1A, a piston rod 4 which can be raised and lowered independently of the lower mold 1A is provided as an opening / closing means for the flow path 2. The piston rod 4 is lifted by a solenoid, a motor or the like (not shown) and held at the top dead center until the molding die 1 is filled with the softened resin and has an appropriate hardness. The top dead center is piston rod 4
The upper end surface 4a of the lower mold 1A is flush with the molding surface 1a of the lower mold 1A, or slightly above or below the molding surface 1a.

The piston rod 4 is formed in a flat cross section so that no gap is formed between the piston rod 4 and the inner surface of the flow path 2. Therefore, when the piston rod 4 is located at the top dead center, the softened resin does not flow into the flow path 2. And lower mold 1
When the semiconductor package 3 is released from A, the piston rod 4 is lowered as shown in FIG.

A compressed air supply path 12 is connected to the flow path 2 of the lower mold 1A. The supply path 12 is connected to a compressed air supply source such as a high pressure gas cylinder (not shown). The compressed air flow path 2 and the supply path 12 are connected at a position between the bottom dead center and the top dead center of the piston rod 4 (see FIGS. 1 and 3). Therefore, when the piston rod 4 descends as described above, the supply passage 12 opens in the flow passage 2, and the flow passage 2 and the supply passage 12 are connected and connected. As a result, compressed air sent from a high-pressure gas cylinder or the like via the supply path 12 is supplied into the flow path 2, and an upward force acts on the semiconductor package 3 to separate the semiconductor package 3 from the lower mold 1A. It

The lower die 1A and the piston rod 4 are made of a material that has pressure resistance and does not allow compressed air to permeate, such as metal or ceramics. Although not shown, the pressure of the compressed air is adjusted by a pressure reducing valve or the like. The pressure reducing valve and the like are provided, for example, between the high pressure gas cylinder and the like and the compressed air supply path 12. The pressure reducing valve such as a high-pressure gas cylinder, the flow path 2 and the supply path 12 have a function as compressed air supply means.

The upper die 1B is provided with a holding rod 11 which can be moved up and down independently of the upper die 1B by a solenoid, a motor or the like. The presser bar 11 is held at the bottom dead center from the step of filling the molding die 1 with the resin to the step of releasing the upper die 1B, pressing the semiconductor package 3 from above.
B can be easily released (see FIGS. 1 and 2).
reference). As the mold hydraulic press device including the upper mold 1B and the lower mold 1A in this example, a structure in which the lower mold 1A moves up and down without moving the upper mold 1B up and down is used.

Next, a method of manufacturing the semiconductor package 3 using the molding apparatus having the above structure will be described. First, the lower die 1A and the upper die 1B are fitted between them by sandwiching a lead frame (portion to be an IC pin) 52 on which a semiconductor chip 51 is die-bonded on the island 5. Although the island 5 and the lead frame 52 are illustrated as being integrated, in reality, the island 5 is formed by punching or etching one plate.
Leadframes 52 are formed around the
The island 5 and the lead frame 52 are fixed to the peripheral edge of the plate, respectively, and the two are separated by cutting off the peripheral edge of the plate after molding.

Next, the piston rod 4 is raised to the top dead center, the pressing rod 15 is lowered to the bottom dead center, and the molding die 1 is heated and maintained at a predetermined temperature. Resin is filled in the mold 1 by a filling means (not shown). The state thus far is shown in FIG.

Then, the mold 1 is held at a predetermined curing temperature to cure the resin in the mold 1, and when a predetermined time elapses in that state, the presser bar 11 is interlocked with the movement of the lower mold 1A. , Lower mold 1A (that is, relatively lower mold 1
Raise B). The semiconductor package 3 does not float because it is adhered to the lower mold 1A and is pressed by the presser bar 11, so that the semiconductor package 3 is easily released from the upper mold 1B. At that time, the piston rod 4 is still held at the top dead center. The state thus far is shown in FIG. In addition,
The curing temperature and the time required for curing the resin are selected in advance by preliminary experiments and the like.

After releasing the upper mold 1B, the piston rod 4 is lowered. As a result, the compressed air flow path 2 and the supply path 12 are communicatively connected. Then, a valve such as a high pressure gas cylinder is opened, and compressed air adjusted to a predetermined pressure by the pressure reducing valve is sent to the supply passage 12. The compressed air sent to the supply path 12 flows into the flow path 2 opened by the downward movement of the piston rod 4, and exerts an upward force (pressure) on the semiconductor package 3.
The state thus far is shown in FIG. The semiconductor package 3 is pushed up by the ejection of compressed air against the adhesive force between the resin and the molding surface of the lower mold 1A, whereby the lower mold 1A is pressed.
And the semiconductor package 3 is obtained as a single body.

Here, the pressure of the compressed air is set to such a magnitude that the semiconductor package 3 is released from the mold and the semiconductor package 3 does not jump out of the lower mold 1A, for example, 5 kg / kg. The size is set to about cm ² . After releasing the lower mold 1A, stop the supply of compressed air,
The piston rod 4 is lifted to return to the initial state, and the resin filling process of the next cycle is prepared.

In the above molding method, as shown in FIG. 3 to the state shown in FIG. 4, the piston rod 4 is lifted again to compress the air in the flow path 2 so that a higher pressure is applied. Then, the semiconductor package 3 may be released from the lower mold 1A. In this case, air at normal pressure is introduced into the flow path 11 instead of compressed air by introducing it forcibly or by using the negative pressure generated by the lowering of the piston rod 4, and the introduced normal pressure is reduced. The air may be compressed by raising the piston rod 4.

According to the above-described embodiment, since the semiconductor package 3 is separated from the lower mold 1A by the compressed air, the stress concentration at the time of mold release is relaxed and the hardness of the semiconductor package 5 is not so high. However, since the mold release can be performed without the generation of cracks, the curing time (the time from the injection of the resin to the release) can be shortened, and the throughput can be improved. Since the semiconductor package 3 is thin, for example, about 1 mm, the semiconductor chip 51
Although stress is likely to be concentrated on the interface between the peripheral island 5 and the resin, peeling of the interface is less likely to occur due to the relaxation of the stress concentration at the time of mold release, and the reliability of the semiconductor package 3 is improved. Further, since a large stress is not locally applied at the time of releasing, it is not necessary to add a releasing agent such as wax into the resin, or the addition amount is small. Therefore, there is an advantage that the bonding strength between the resin of the semiconductor package 3 and the leads is increased, and the strength of the entire package is improved.

Here, although the reason why the generation of cracks can be prevented by releasing the lower mold from the compressed air is not clear, the present inventors presume as follows.
That is, when the conventional molding apparatus shown in FIG. 9 is used, when the semiconductor package 3 is pushed up by the pins 10, the lower part of the lower die 1 is not lifted up and the part of the semiconductor package 3 is lifted up.
A large shear stress is generated between the part and the part that is in close contact with A. Then, the shear stress causes the generation of cracks. On the other hand, according to the present invention, the semiconductor package 3 is pushed up by the compressed air and slightly lifted from the lower mold 1A, and at the same time, the entire gap created between the semiconductor package 3 and the lower mold 1A is lifted by the compressed air. It is filled. Thereby, the lower die 1A of the semiconductor package 3 is
Since the pressure of the compressed air acts uniformly on the entire portion in contact with the gap formed between the semiconductor package 3 and
It is considered that the shearing stress generated in (1) becomes significantly smaller than that in the case of the conventional device, and cracks do not occur.

FIG. 5 shows another example of the semiconductor package molding apparatus. The molding apparatus of the second embodiment is different from that of the first embodiment in that as a means for opening and closing the compressed air flow path 2, instead of the piston rod 4 of the first embodiment, a lower mold 1A is used. A cylinder 6 that can be independently raised and lowered and a valve body 6 that opens and closes an opening 61 (see FIG. 7) at the upper end of the cylinder 6.
2 and 2 are provided. The rest of the configuration is the same as that of the first embodiment, so the same reference numerals are given and the description thereof is omitted.

In this molding apparatus, the cylindrical body 6 is raised by a solenoid, a motor or the like (not shown) and held at the top dead center until the molding die 1 is filled with the softened resin and has an appropriate hardness. At the top dead center, the upper end surface 63 of the tubular body 6 is flush with the molding surface 1a of the lower mold 1A, or slightly.
The position is above or below. Further, the valve body 62 is fixed to the lower mold 1A at a position such that the upper end surface 64 thereof is flush with the molding surface 1a of the lower mold 1A or slightly above or below the molding surface 1a.

The cylindrical body 6 is formed so that its outer side surface 65 is substantially in contact with the inner surface of the flow path 2. Further, the upper end surface 64 of the valve body 62 is formed in a shape that can exactly close the opening 61 of the upper end surface 63 of the tubular body 6, as shown in FIG. 7. Therefore, when the cylinder body 6 is located at the top dead center (see FIG. 7).
2), the gap between the valve body 62 and the flow path 2 is closed by the cylindrical body 6, so that the softened resin does not flow into the flow path 2.

After releasing the upper die 1B, when the semiconductor package 3 is released from the lower die 1A, the cylindrical body 6 is lowered as shown in FIG. The valve body 62 is formed such that the lower portion is thinner than the upper portion. Therefore, the lower end of the tubular body 6 opens the opening 61 at its upper end. As a result, an upward force acts on the semiconductor package 3 by the compressed air sent from the high-pressure gas cylinder or the like into the flow path 2,
The semiconductor package 3 is released from the lower mold 1A. Lower mold 1
After the mold release of A, the tubular body 6 is lifted and returned to the initial state.

The cylinder body 6 and the valve body 62 are made of a material that has pressure resistance and does not allow compressed air to pass therethrough, such as metal or ceramics. The pressure of the compressed air is adjusted by, for example, a pressure reducing valve (not shown) provided between the high pressure gas cylinder or the like and the compressed air passage 2.

FIG. 8 shows still another example of the semiconductor package molding apparatus. The molding apparatus of the third embodiment differs from that of the first embodiment in that the flow path 2 for compressed air is blocked by a selective permeation plate 7 which is impermeable to resin but permeable to gas. That is the point. The selective permeation plate 7 has a function as a closing means, and the lower mold 1A
It is fixed to. The other configurations are the same as those of the first embodiment, and therefore, the same reference numerals are given and the description thereof is omitted.

The selective permeation plate 7 preferably has a characteristic that, in addition to the selective permeation performance described above, the adhesiveness to the cured resin is low. Then, the adhesive action between the selective transmission plate 7 and the resin does not impair the releasability of the semiconductor package 3 from the lower mold 1A. Specifically, as the material of the selective transmission plate 7, a trade name “GORE-TEX” (manufactured by Japan GORE-TEX Co., Ltd.), a vent filter, or the like can be used. "Goretex" is
PTFE is specially processed into a continuous porous body, and the liquid content is repelled on the surface and only gas is allowed to pass through. The vent filter is a filter whose purpose is to adjust the internal pressure and external pressure of the container due to temperature changes.

When a semiconductor package is manufactured using the molding apparatus of the third embodiment, a high-pressure gas cylinder or the like is used when releasing the semiconductor package 3 from the lower die 1A after releasing the upper die 1B. It suffices to open the valve of 2 and send the compressed air to the flow path 2 of the lower mold 1A. Then, after the lower mold 1B is released, the supply of compressed air may be stopped. In the third embodiment, the lower die 1A has a movable member (the first
Since the piston rod 4 of the embodiment and the cylindrical body 6) of the second embodiment are not provided, there is an effect that the structure thereof is simplified. The means for opening and closing the flow path 2 of the lower mold 1A is not limited to the piston rod 4, the cylinder body 6 and the valve body 62, and the flow path 2 can be opened to eject compressed air when the lower mold 1A is released. In addition, as long as the flow path 2 is closed when the molding die 1 is filled with the resin and cured, any structure may be used. Further, not limited to compressed air, an inert gas such as argon or a high pressure gas such as nitrogen gas may be used. Furthermore, a plurality of compressed air flow paths 2 may be provided.

Furthermore, in each of the above embodiments, the case where the present invention is applied to molding of a semiconductor package has been described, but the present invention is not limited to this, and the present invention can be used for molding of various products.

[0034]

According to the present invention, since the molded body is separated from the molding die by the compressed air, the concentration of stress on a specific portion of the molded body at the time of mold release is relieved. Therefore, even if the hardness of the molded body is not as high as in the conventional case, it is possible to release the molded body without causing cracks, so that the curing time (the time until the release of the molded body is started) can be shortened. In particular, when molding a semiconductor package, the interface between the island and the molding material in the vicinity of the peripheral edge of the semiconductor chip is likely to peel off, so that a large stress is not locally applied to the package at the time of mold release. Peeling can be prevented, and the reliability of the semiconductor package is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a molding apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing a state where the upper mold of the molding apparatus is released from the mold.

FIG. 3 is a cross-sectional view showing a state where the lower mold of the molding apparatus is being released.

FIG. 4 is a cross-sectional view showing a second state in which the lower mold of the molding apparatus is released from the mold.

FIG. 5 is a cross-sectional view showing another example of the molding apparatus according to the present invention.

FIG. 6 is a cross-sectional view showing a state where the lower mold of the molding apparatus is being released.

FIG. 7 is a perspective view showing a main part of the molding apparatus.

FIG. 8 is a sectional view showing still another example of the molding apparatus according to the present invention.

FIG. 9 is a cross-sectional view showing a conventional molding device.

[Explanation of symbols]

 1 Molding Mold 1A Lower Mold 1B Upper Mold 1a Molding Surface 5 Semiconductor Package 10 Flow Path (Compressed Air Supply Means) 11 Piston Rod (Opening / Closing Means) 12 Supply Path (Compressed Air Supplying Means) 13 Cylindrical Body (Opening / Closing Means) 14 Valve Body (Opening / closing means) 7 Selective transmission plate (closing means) 51 Semiconductor chip 52 Lead frame

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication // B29L 31:34

Claims (4)

[Claims] 1. At least one mold and the other mold 2
In a molding method in which molds divided into two are combined, a mold material is filled in the combined mold and cured, and then a molded body made of the cured mold material is released, And a step of releasing the molded body from the other mold by introducing compressed air between the other mold and the molded body. Molding method characterized by. 2. At least one die and the other die 2
In a molding method in which a semiconductor chip supported on a frame is inserted into a mold divided into two, a mold material is filled, and a package made of the mold material is released after the mold material is cured, A step of releasing the package from the one mold, and a step of releasing the package from the other mold by introducing compressed air between the other mold and the package. A method for molding a package for a semiconductor integrated circuit device, comprising: 3. At least one die and the other die 2
In a molding apparatus in which a semiconductor chip supported on a frame is inserted into a mold divided into two parts, a mold material is filled, and a package made of the mold material is released after the mold material is cured, At least one flow path that opens in the molding surface of the other mold and through which compressed air flows, compressed air supply means that supplies compressed air into the flow path, and the opening of the flow path can be opened and closed. The opening / closing means closes the opening of the flow path when the molding material is filled in the molding die, and the package made of the cured molding material is released from the other mold. A molding device for a package for a semiconductor integrated circuit device, which is configured to open the opening so that the flow path communicates with a molding surface of the other mold when the molding is performed. 4. Two of at least one mold and the other mold
In a molding apparatus in which a semiconductor chip supported on a frame is inserted into a mold divided into two parts, a mold material is filled, and a package made of the mold material is released after the mold material is cured, At least one flow path that opens in the molding surface of the other mold and through which compressed air flows, compressed air supply means that supplies compressed air into the flow path, and closes the opening of the flow path. And a closing means made of a material that is impermeable to the molding material but permeable to gas, and a molding device for a package for a semiconductor integrated circuit device.