JP4065148B2 - Resin molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin molding method used when a molten resin is injected into a cavity of at least one of opposed molds to produce a molded product.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in resin molding in which molten resin is pressurized and injected into a cavity, so-called transfer molding, a mold for resin molding, which is a die opposite to each other and at least one of which is provided with a cavity, is used. This mold is made of, for example, a steel material such as tool steel.
[0003]
However, the conventional mold has a problem that bubbles contained in the molten resin are difficult to escape from the cavity after the mold is clamped. Therefore, such bubbles remain and voids may occur in the cured resin obtained by curing the molten resin. And the void which generate | occur | produced in cured resin may impair the external appearance of a molded article. In addition, for molded products in which chip-shaped electronic components mounted on a lead frame, a printed circuit board, or the like (hereinafter referred to as a substrate) are sealed, there is a risk of reducing the yield and reliability of the molded products, that is, packages. There is.
[0004]
The present invention has been made to solve the problems described above, and an object thereof is to provide a resin molding method to suppress the generation of voids in the molded article.
[0005]
[Means for Solving the Problems]
In order to solve the above technical problem, a resin molding method according to the present invention is a resin molding method for producing a molded product by curing a molten resin in a cavity of at least one of opposing molds, A process of clamping a mold comprising a porous member having at least a part of a cavity surface of the cavity and having a continuous porosity as a mold facing each other; a process of pressurizing and injecting molten resin into the cavity; the gas in the interior of the cavity, characterized by comprising the steps of: via the porous member is discharged to the outside of the cavitation I by pressurized injection of molten resin into the cavity.
[0006]
According to this, when the molten resin is pressurized and injected into the cavity, the gas existing inside the cavity is injected into the cavity by pressurizing and injecting the molten resin to the outside of the cavity via the porous member. Can be discharged.
[0007]
Moreover, the resin molding method according to the present invention includes a step of stretching a resin molding film having continuous porosity between opposing molds before the step of clamping in the resin molding method described above, In the discharging step, the gas existing inside the cavity is discharged through the resin molding film and the porous member sequentially.
[0008]
According to this, when the molten resin is pressurized and injected into the cavity, the gas existing inside the cavity can be discharged through the resin molding film and the porous member sequentially to the outside of the cavity. . Further, the presence of the resin molding film can prevent clogging of the porous member and adhesion of dirt or the like on the cavity surface.
[0009]
In the resin molding method according to the present invention, in the resin molding method described above, in the discharging step, the gas existing inside the cavity is discharged by further pressurizing the molten resin after filling the cavity with the molten resin. It is characterized by.
[0010]
According to this, by further pressurizing the molten resin filled in the cavity, the gas existing inside the cavity including bubbles in the molten resin can be discharged outside the cavity through the porous member. it can.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
As an example of resin molding, a case where an electronic component such as a semiconductor chip mounted on a substrate is resin-sealed will be described as an example. Hereinafter, a resin mold used in the resin molding method according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 (1) is a cross-sectional view showing a state where a resin mold used in the resin molding method according to the present embodiment is opened, and FIG. 1 (2) shows the vicinity of part A in FIG. 1 (1). It is an expanded sectional view. 2 (1) and 2 (2) show a state in which the molten resin is injected into the cavity after the resin mold of FIG. 1 is clamped and the molten resin filled in the cavity is further pressurized. It is sectional drawing which shows a state, respectively.
[0012]
In FIG. 1A, an upper mold 1 and a lower mold 2 are provided to face each other, and the upper mold 1 and the lower mold 2 together constitute a resin mold. Of these, the upper mold 1 characterizes the resin mold according to the present invention. A substrate 3 such as a lead frame or a printed circuit board is placed on the lower mold 2. A chip 4 made of an electronic component such as a semiconductor chip is mounted on the substrate 3, and electrodes of the substrate 3 and the chip 4 are electrically connected by a wire 5.
The upper mold 1 is provided with a space that covers the chip 4 and the wire 5, that is, a cavity 6 and a gate 7 that is a space communicating with the cavity 6. As will be described later, the molten resin is injected into the cavity 6 through the gate 7 and cured, thereby forming a cured resin.
[0013]
Further, the upper die 1 is provided with a through hole 8 on the surface of the cavity 6, that is, on the upper surface of the cavity surface. The through hole 8 is provided with a ceramic member 9 having continuous porosity as a porous member, and the lower surface of the ceramic member 9 constitutes a part of the upper surface of the cavity 6. The fixing block 10 is fixed to the upper surface of the ceramic member 9. The fixing block 10 is provided with a concave portion 11 on the surface in contact with the upper surface of the ceramic member 9, and the concave portion 11 is opened to the outside of the cavity 6, in other words, to the outside of the resin molding die through the pipe 12. .
[0014]
Hereinafter, the structure of the ceramic member 9 will be described with reference to FIG. In FIG. 1 (2), the hollow ceramic particles 13 are minute hollow spheres having, for example, silica and alumina as main components and having a high melting point (for example, about 1500 ° C. to 1600 ° C.). The connecting portion 14 is an inorganic member formed in a film shape on the surface of the hollow ceramic particle body 13 and connected to the hollow ceramic particle body 13 in a mesh shape. The connecting portion 14 is mainly composed of a material having a melting point lower than the melting point of the hollow ceramic particles 13, for example, a silicate compound such as sodium silicate. The gap 15 is a space formed in the connecting portion 14, and the presence of the gap 15 in the connecting portion 14 allows the ceramic member 9 to have continuous porosity and air permeability.
[0015]
The ceramic member 9 is manufactured by, for example, firing at a temperature of about 1200 ° C. to 1300 ° C. after mixing and kneading the hollow ceramic particles 13 and the raw material of the connecting portion 14. This firing temperature is lower than the melting point of the material of the hollow ceramic particles 13 and higher than the melting point of the material of the connecting portion 14.
[0016]
The coating portion 16 is a film formed on the surface of the ceramic member 9 on the surface constituting the cavity surface of the ceramic member 9. The coating portion 16 is made of a material having low adhesion to the cured resin obtained by curing the molten resin, such as a glaze, a fluoropolymer hard film, TiC, TiN, diamond-like carbon, or the like.
[0017]
By the way, when the ceramic member 9 shown in FIG. 1 (2) is manufactured, the outer diameter of the hollow ceramic particles 13 and the quantity per unit volume of the ceramic member 9, and the inorganic material constituting the connecting portion 14 The amount can be changed appropriately. Thus, the size of the gap 15 in the cavity surface, that is, the diameter of the opening formed in the cavity surface and the surface roughness of the cavity surface can be appropriately determined. Therefore, the surface roughness of the molded product can be easily set and changed by exchanging the ceramic member 9.
[0018]
Here, the first feature of the resin mold used in the resin molding method according to the present embodiment is that the ceramic member 9 is manufactured such that the gap 15 satisfies the following conditions. . That is, the diameter of the gap 15 is sufficiently small to prevent the molten resin particles injected into the cavity 6 from passing therethrough. The diameter of the gap 15 is sufficiently large so that gas molecules existing in the cavity 6 can pass through in a state where the molten resin is pressurized and injected into the cavity 6. Here, the gas is composed of a gas in a portion not filled with the molten resin in the cavity 6, a gas derived from the molten resin and volatilized from there, a bubble taken into the molten resin, and the like. Therefore, the gas existing in the cavity 6 including bubbles in the molten resin is discharged to the outside of the cavity 6 through the gap 15. On the other hand, the molten resin remains inside the cavity 6.
The second feature is that a film-like coating portion 16 having low adhesion to the cured resin is formed on the surface of the ceramic member 9 on the cavity surface. Thereby, the mold release property between the cured resin and the resin mold is improved.
[0019]
Hereinafter, the operation of the resin mold according to this embodiment will be described with reference to FIG. In FIG. 2A, molten resin 17 is injected into the cavity 6 through the gate 7 with the upper mold 1 and the lower mold 2 being clamped. As a result, the bubbles 18 contained in the molten resin 17 are degassed little by little. Therefore, the gas existing inside the cavity 6 includes a gas in a portion not filled with the molten resin 17 in the cavity 6, a gas volatilized from the molten resin 17, and a part of the bubbles 18. And the gas which exists in the inside of the cavity 6 is discharged | emitted outside the cavity 6 through the recessed part 11 and the pipe line 12 in order.
[0020]
In FIG. 2 (2), after the molten resin 17 is filled in the cavity 6, the molten resin 17 is further pressurized for a certain time. Thereby, the bubbles 18 remaining inside the molten resin 17 are defoamed. Thereafter, the molten resin 17 is cured to form a cured resin. Then, after the upper mold 1 and the lower mold 2 are opened, a molded product in which the cured resin and the substrate 3 are integrated is taken out from the resin mold. Here, as shown in FIG. 1B, a film-like coating portion 16 having low adhesion to the cured resin is formed on the surface of the ceramic member 9 on the cavity surface. Therefore, the molded product can be easily taken out and adhesion of dirt and the like on the cavity surface can be minimized.
[0021]
As described above, according to this embodiment, the gas in the cavity 6 including the bubbles 18 contained in the molten resin 17 is discharged to the outside of the cavity 6. Therefore, the generation of voids in the molded product is suppressed.
Further, the coating part 16 formed on the cavity surface allows the molded product to be easily taken out and prevents the deposits from adhering to the cavity surface.
In addition, the hollow ceramic particles 13 and the gaps 15 can reduce the weight of the resin mold.
[0022]
Of the ceramic member 9 shown in FIG. 1 (2), the cured resin and the ceramic member depend on the material and surface state of the hollow ceramic particles 13 and the connecting portion 14 and the characteristics of the molten resin 17. In some cases, the adhesiveness to 9 does not increase so much. In this case, it is not always necessary to form the coating portion 16 on the surface of the ceramic member 9 on the cavity surface.
[0023]
In addition, as a porous member in which a large number of continuous holes are formed, a ceramic member 9 which is composed of hollow ceramic particles 13 and connecting portions 14 and has continuous porosity is used. Not only this but the continuous porous member which consists of inorganic hollow granular materials other than a ceramic, and the connection part 14 can also be used.
[0024]
(Second Embodiment)
The resin molding film used in the resin molding method according to the second embodiment of the present invention will be described with reference to FIG. 3 (1) and 3 (2) show that in the resin molding method according to the present embodiment, after the resin molding film is stretched and the resin molding die is clamped, the molten resin filled in the cavity is further pressurized. It is sectional drawing which shows the state which has been pressed, and the state which the pressurization with respect to the molten resin with which the cavity was filled was completed, respectively.
[0025]
In FIG. 3A, a resin molding film 19 is stretched between the upper mold 1 and the lower mold 2 in a state where the mold is opened. The film 19 is pressed against the cavity surface of the cavity 6 by the molten resin 17 injected into the cavity 6 while being stretched with a constant tension. Then, at the stage where the injection of the molten resin 17 into the cavity 6 is completed, the film 19 exists along the cavity surface without wrinkles, as shown in FIG.
[0026]
The film 19 is a continuous porous film having air permeability, for example, made of a fluorine resin such as PTFE having excellent releasability and having a large number of minute continuous holes. The diameter of these continuous holes is sufficiently small so that the particles of the molten resin 17 injected into the cavity 6 cannot pass through. The diameter of the continuous hole is sufficiently large to allow gas molecules existing in the cavity 6 to pass through in a state where the molten resin 17 is pressurized and injected into the cavity 6.
[0027]
Here, the first feature of the present embodiment is that the film 19 is uniformly adhered to the entire cavity surface without wrinkles by being pressed by the injected molten resin 17. is there. Therefore, since the generation of wrinkles in the film 19 is suppressed, the deterioration of the appearance quality due to the transfer of the wrinkles of the film 19 to the surface of the molded product is prevented. This effect is particularly remarkable when the molded product is large. Conventionally, the film 19 needs to have a certain thickness in order to suppress wrinkles. However, according to the present embodiment, the thin film 19 can be used.
The second feature is that bubbles 18 in molten resin 17 are degassed by pressurizing filled molten resin 17 for a certain period of time. Thereby, the gas in the cavity 6 including the bubbles 18 is discharged to the outside of the cavity 6 through the film 19, the ceramic member 9, the recess 11, and the conduit 12 in order. Therefore, as shown in FIG. 3B, at the stage where the pressurization to the filled molten resin 17 is completed, the bubbles in the molten resin 17 are defoamed and thus do not exist.
The third feature is that the film 19 is made of a fluorine resin such as PTFE having excellent releasability. Therefore, the mold release property between the cured resin and the film 19 becomes good, so that the molded product can be easily taken out. Further, the presence of the film 19 prevents clogging of the ceramic member 9 and adhesion of dirt or the like on the cavity surface.
[0028]
As described above, according to the present embodiment, as in the first embodiment, generation of voids in the molded product is suppressed, and the weight of the resin mold can be reduced. Further, since the generation of wrinkles in the film 19 is suppressed, the appearance quality of the molded product is prevented from being deteriorated. Further, since a thinner film than the conventional one can be used, the material cost can be reduced and the apparatus can be simplified. Further, the molded product can be easily taken out, and clogging of the ceramic member 9 and adhesion of dirt and the like on the cavity surface can be prevented.
[0029]
By the way, according to the present embodiment, the surface roughness of the molded product can be easily set and changed as follows. First, the surface roughness of the ceramic member 9 can be changed as described with reference to FIG. 1B in the first embodiment. Further, since the film 19 is pressed by the molten resin 17 in a state of being stretched with a constant tension, the film 19 is uniformly adhered to the cavity surface including the surface of the ceramic member 9 without generating wrinkles. . Moreover, a thinner film than before can be used. As a result, the surface roughness of the ceramic member 9 is accurately transferred to the surface of the molded product via the film 19. Therefore, since the molded product has a surface roughness corresponding to the surface roughness of the ceramic member 9, the surface roughness of the molded product can be easily set and changed by replacing the ceramic member 9.
[0030]
In addition, a high-pressure gas source can be connected to the recess 11 via a pipe. In this case, after the resin molding is completed, for example, high-pressure air is jetted into the cavity 6 via the ceramic member 9. Thus, the molded product is uniformly pressed on the wide surface of the cavity 6 without using a protruding mechanism such as a pin. Accordingly, since the molded product is ejected without causing local stress in the molded product, it is possible to prevent the occurrence of cracks and the like in the molded product.
[0031]
Further, for reasons such as the characteristics of the molten resin 17 and other reasons, pressurization to the molten resin 17 after filling can be omitted as long as the bubbles in the molten resin 17 do not become a problem. In this case, when the molten resin 17 is pressurized when injected into the cavity 6, the gas present inside the cavity 6 is discharged to the outside of the cavity 6.
[0032]
Further, the lower surface of the ceramic member 9 constitutes a part of the upper surface of the cavity 6. Not limited to this, the lower surface of the ceramic member 9 may constitute the entire upper surface of the cavity 6. Furthermore, all of the cavity surfaces may be constituted by the surface of the ceramic member 9. As a result, the weight of the resin mold can be further reduced.
[0033]
Further, when the resin mold is used for a long time, deposits such as dirt made of organic matter gradually adhere to the cavity surface. Even when the film 19 is used as shown in FIG. 3, the gas component that has passed through the film 19 may adhere to and accumulate on the cavity surface. Further, since deposits accumulate on the inner wall portion of the gap 15, the air permeability of the ceramic member 9 is lowered. Therefore, the bubbles 18 are not easily discharged outside the cavity 6. In this case, the ceramic member 9 may be removed and the ceramic member 9 may be left in a high temperature atmosphere lower than the firing temperature for a certain period of time. As a result, the deposit made of an organic substance volatilizes and is removed from the inner wall of the gap 15, so that the air permeability of the ceramic member 9 is restored.
[0034]
Further, the case where the chip 4 is resin-sealed in the state where the electrodes of the substrate 3 and the chip 4 are electrically connected by the wire 5 has been described as an example. The present invention is not limited to this, and the present invention can also be applied to the case where resin sealing is performed in a state in which the electrodes of the substrate 3 and the chip 4 are connected to face each other, that is, in a so-called flip chip bonding state. Furthermore, the present invention can be applied to other than resin molding for sealing electronic components.
[0035]
Further, the present invention is not limited to the above-described embodiment, and can be arbitrarily changed and selected as needed within a range not departing from the gist of the present invention.
[0036]
【The invention's effect】
According to the present invention, the bubbles contained in the molten resin injected into the cavity are degassed and discharged together with the gas in the cavity to the outside of the cavity. Further, the weight of the resin mold can be reduced. In addition, the releasability between the cured resin and the resin mold is improved. Further, the resin molding film that is uniformly adhered to the cavity surface suppresses the generation of wrinkles in the molded product and prevents clogging of the porous member and adhesion of dirt and the like on the cavity surface.
By these, this invention can provide the resin molding method which prevents generation | occurrence | production of the void in a molded article, and the fall of an external appearance quality, improves the mold release property with respect to cured resin, and also enables weight reduction of a resin mold. It has an excellent practical effect.
[Brief description of the drawings]
FIG. 1 (1) is a cross-sectional view showing a state in which a resin mold used in the resin molding method according to the first embodiment of the present invention is opened, and FIG. It is sectional drawing which expands and shows the A section vicinity of (1).
FIGS. 2 (1) and 2 (2) show a state in which the molten resin is injected into the cavity after the resin mold of FIG. 1 is clamped, and the molten resin filled in the cavity is further pressurized. It is sectional drawing which shows each state.
FIGS. 3 (1) and 3 (2) show a method for filling a cavity after a resin molding film is stretched and a resin mold is clamped in a resin molding method according to a second embodiment of the present invention. FIG. 4 is a cross-sectional view showing a state where the molten resin is further pressurized and a state where pressurization of the molten resin filled in the cavity is completed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Upper mold | type 2 Lower mold | type 3 Board | substrate 4 Chip 5 Wire 6 Cavity 7 Gate 8 Through-hole 9 Ceramic member (porous member)
DESCRIPTION OF SYMBOLS 10 Fixing block 11 Concave part 12 Pipe line 13 Hollow ceramic particle (inorganic particle)
14 connecting part 15 gap 16 coating part 17 molten resin 18 bubble 19 film (film for resin molding)

Claims (3)

A resin molding method for producing a molded product by curing a molten resin in a cavity of at least one of opposing molds,
A step of clamping a mold comprising a porous member having at least a part of a cavity surface of the cavity and having a continuous porosity as the opposing mold;
Pressurizing and injecting the molten resin into the cavity;
A step of discharging the gas existing inside the cavity to the outside of the cavity through the porous member by pressurizing and injecting the molten resin into the cavity. Method. In the resin molding method of Claim 1,
And including a step of stretching a resin molding film having continuous porosity between the opposing molds before the step of clamping the mold,
In the discharging step, the gas present in the cavity is discharged through the resin molding film and the porous member sequentially. In the resin molding method according to claim 1 or 2,
In the discharging step, the resin existing in the cavity is discharged by further pressurizing the molten resin after filling the cavity with the molten resin.

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