JP5255900B2 - Mold and manufacturing method thereof - Google Patents

Description

  The present invention relates to a mold for clamping a workpiece carried in alignment with a cavity recess, filling the cavity recess with resin, and sealing the workpiece with resin, and a method for manufacturing the same.

A cavity recess is formed in a mold for resin-sealing a workpiece such as a semiconductor component. The work is aligned with the cavity recess and carried into the mold, clamped by the mold, and filled into the cavity recess.
The cavity recess of the mold is formed by electric discharge machining with an electric discharge machine. At this time, the bottom surface of the cavity and the side surface of the cavity surrounding the periphery have been processed with the same discharge surface roughness by electric discharge machining.

In addition, the surface roughness of the surface of the resin-sealed package is required to have a surface roughness and surface properties with less light reflection during image processing by printing a product name or appearance inspection. Also, so-called green resin is used to reduce the environmental burden. While green resin has stronger adhesion to the mold than conventional resin materials, the entire package (resin-sealed part) tends to be partially unstable in the cured state and adheres to the mold recess. There is a possibility that it will grow as a dirt anchor or grow larger and become an obstacle to mold release. In particular, the problem of resin peeling is remarkable on the side surface of the package.
JP 2003-25336 A

  It is known that the mold release performance is improved by smoothing the side surface surrounding the bottom surface of the cavity recess. It is also conceivable to polish the side surface of the cavity by machining (lapping process) to make a mirror surface. However, if lapping is performed on all the side surfaces (four surfaces) of all the cavity recesses carved in the mold, it takes time and production is difficult because uniform finishing is difficult.

The applicant of the present application has found that the surface properties of the processed surface are reversed by devising the processing conditions of the cavity recess of the mold, and has come to the present invention.
An object of the present invention is to solve the above-described problems and provide a mold having improved releasability by changing processing conditions of a bottom surface portion and a side surface portion for forming a cavity recess and a method for manufacturing the same.

In order to achieve the above object, the present invention comprises the following arrangement.
A mold that clamps a workpiece carried in alignment with a cavity recess, and is filled with sealing resin into the cavity recess to seal the workpiece with resin, and includes processing that includes electric discharge machining on the die base material Among the cavity recesses formed through the process, the surface roughness of the bottom surface of the cavity is in the range of 2.5 (Ra) to 1.5 (Ra) in terms of centerline average roughness (Ra). The cavity side surface surrounding this is subjected to secondary electrical discharge machining with different machining conditions, and the surface roughness is in the range of 0.5 (μRa) to 0.3 (μRa) in terms of centerline average roughness (Ra). The cavity side surface has a cross-sectional shape in which a peripheral surface is surrounded by a groove portion and a convex surface portion having a convex inside is formed on a smooth surface continuous through the groove portion, thereby reducing the amount of resin remaining in the groove portion. Release the molded product from the cavity recess The shearing force at the time is reduced .
Also, the cavity side surface portion, characterized in that the laser processing instead of the secondary electric discharge machining is formed on the smooth surface the smaller surface roughness than the cavity bottom portion is subjected.
Further, the cavity side surface portion is formed as a smooth surface having a surface roughness smaller than that of the cavity bottom surface portion by performing chemical polishing instead of the secondary electric discharge machining .
It is characterized by that.

A method of manufacturing a mold for clamping a work carried in alignment with a cavity recess, filling the cavity recess with a sealing resin, and sealing the work with a resin, wherein the discharge electrode is adapted to the work shape of the work Is subjected to primary electrical discharge machining so that the cavity bottom surface portion of the cavity recess and the cavity side surface surrounding the cavity bottom surface portion have a centerline average roughness (Ra) of 2.5 (Ra). The step of forming the cavity recess so as to have a surface roughness in the range of ˜1.5 (Ra) and the secondary discharge machining by narrowing the gap of the discharge electrode with respect to the cavity side surface surrounding the cavity bottom surface The surface roughness is in the range of 0.5 (μRa) to 0.3 (μRa) in terms of the centerline average roughness (Ra), and the peripheral shape of the cross-sectional shape of the side surface of the cavity is surrounded by a groove. Including a step of forming a convex surface portion having an inner convex portion on a smooth surface continuous through the groove portion, and reducing a residual resin amount remaining in the groove portion to release a molded product from the cavity concave portion. It is characterized by reducing .
Further, instead of the secondary electric discharge machining, laser processing is performed on the side surface portion of the cavity, and the convex surface portion in which the inside surrounded by the groove portion is convex has a surface roughness smaller than that of the cavity bottom surface portion connected through the groove portion. The method includes a step of forming a surface.
Further, instead of the secondary electric discharge machining, the side surface portion of the cavity is subjected to chemical polishing, and the convex surface portion in which the inside surrounded by the groove portion is convex has a surface roughness smaller than that of the bottom surface portion of the cavity connected through the groove portion. The method includes a step of forming a smooth surface.
Further, instead of the secondary electric discharge machining, the cavity side surface portion is subjected to electropolishing processing, and the convex surface portion in which the inside surrounded by the groove portion is convex is smaller in surface roughness than the cavity bottom surface portion connected through the groove portion. The method includes a step of forming a smooth surface.

By using the mold according to the present invention and the manufacturing method thereof, an electric discharge machining surface having different surface roughness and surface properties is formed between the cavity bottom surface portion forming the cavity recess and the cavity side surface portion surrounding the cavity bottom surface portion. When the mold resin is released, the amount of resin that is caught and sheared by minute irregularities due to the surface characteristics of the cavity side surface of the cavity recess is reduced, and the release force is reduced to improve the release property. be able to. In particular, the mold releasability of a mold resin having a high adhesive strength such as a green resin can be enhanced.
In addition, the cavity side surface where the reverse crater part is connected is formed on a smooth surface with less surface roughness than the bottom surface of the cavity by applying any of electrical discharge machining, laser machining, chemical polishing, or electrolytic polishing with different machining conditions. Has been. Thereby, since the volume which bites into the cavity side part of mold resin reduces, mold release property improves remarkably.
Also, when processing the cavity recess, the bottom surface and side surfaces are roughened by the first electric discharge machining, and only the side surface is mirror-finished by the second processing, thereby shortening the cavity recess processing time. Can do.

Hereinafter, preferred embodiments of a mold according to the present invention and a manufacturing method thereof will be described in detail with reference to the accompanying drawings.
First, a schematic configuration of a mold will be described with reference to FIGS. 1 and 2.
In FIG. 1, a metal mold that is excellent in wear resistance and capable of precision machining is used for the mold, and a conductive material such as a metal raw material, powdered high-speed steel, cemented carbide, zirconia, and yttria ceramic is preferably used. It is done.

The principle of electric discharge machining will be described with reference to the schematic diagram of FIG.
In electric discharge machining, a discharge electrode (for example, a graphite electrode or a copper alloy electrode) 2 having the same shape as a workpiece (mold mold 1) W and a machining shape (cavity recess) is immersed in an insulating working fluid (for example, kerosene) 3. The pulsed arc discharge is repeated. The magnitude of the discharge energy is determined according to the gap G between the workpiece W and the discharge electrode 2. As shown in FIG. 1A, when the gap G is large, the discharge energy is large, and the processed surface has a surface property (rough surface P) in which crater-like recesses are continuous. When the gap is small as shown in FIG. 1 (b), the discharge energy is small, and the processed surface has a surface property (a finely processed surface R) in which inverted crater-like convex portions are continuous.

FIG. 2 shows a schematic diagram when fine electric discharge machining is performed on the mold.
When discharge (arc) occurs between the electrode and the mold in FIG. 2A, the mold surface is rapidly heated and melted in FIG. 2B, and at the same time, the machining liquid 3 is gasified by heating. By this gasification, when the discharge energy is sufficiently large in FIG. 2C, the melted portion 1a of the mold 1 is blown off and removed. However, when the discharge energy is not so large, in FIG. 2 (d), the melted portion is pulled back by the surface tension and solidifies as a reverse crater-like convex portion. When the discharge electrode 2 further approaches the die machining surface, an arc is generated again between the discharge electrode and the die, and the same fine electric discharge machining is performed.

  3A and 3B, electric discharge machining surfaces having different surface roughness and surface properties are formed between the bottom surface portion 5 of the cavity recess 4 of the mold 1 and the side surface portion 6 surrounding the bottom surface portion 5. . FIGS. 3A and 3B illustrate the case where the cavity concave portion 4 has a surface roughness with the cavity bottom surface portion 5 being finished and the cavity side surface portion 6 being precision finished.

Specifically, in FIG. 3A, the entire cavity recess 4 is subjected to primary electric discharge machining to a required surface roughness, and then the same discharge electrode 2 is not discharged to the cavity bottom 5 in FIG. For example, about 20 μm), it is lifted in the Z direction and further moved in the XY direction, and only the side surface portion 6 of the cavity is subjected to secondary electric discharge machining.
Alternatively, after the primary discharge processing is performed on the entire surface of the cavity recess 4 to a desired surface roughness and surface property, the discharge electrode 2 is changed, and the secondary discharge is performed by changing the processing conditions such as the gap between the discharge electrode only on the cavity side surface portion 6. Processing (fine electrical discharge machining) may be performed.

  Furthermore, after performing primary electric discharge machining (fine electric discharge machining) on the entire surface of the cavity recess 4, secondary electric discharge machining is performed on the cavity bottom surface portion 5 using the same discharge electrode 2 so as to obtain desired surface roughness and surface properties. Alternatively, after the primary electric discharge machining (fine electric discharge machining) is performed on the entire surface of the cavity recess 4, the discharge electrode 2 is changed and the machining conditions such as the gap with the discharge electrode are changed only on the cavity bottom surface portion 5. Then, secondary electric discharge machining may be performed to have a desired surface roughness and surface properties.

FIG. 4A shows an enlarged schematic view of the cavity side face portion 6 after the secondary electric discharge machining, and FIGS. 4B and 4C show an arrow AA sectional view and an arrow BB sectional view.
The cross-sectional shape of the cavity side surface portion 6 is formed on a smooth surface where the reverse crater portion 6b whose inner peripheral portion is surrounded by the groove portion 6a is convex. The surface part of the reverse crater part 6b is finished in a flat surface.
Specifically, the surface roughness of the conventional cavity recess 4 is uniform and the centerline average roughness (Ra) is 2.5 (Ra) to 1.5 (Ra). Like a mirror surface with a centerline average roughness (Ra) of 0.5 ([mu] Ra) to 0.3 ([mu] Ra) or a ten-point average roughness (Rz) of 1.2 (Rz) or less on the fine electrical discharge machining surface. The surface was smooth.

5A and 5B are schematic cross-sectional views of the mold release operation of the mold resin (package part). When the mold resin 7 is released in the direction indicated by the arrows in FIGS. 5A and 5B, the amount of resin 7a that is difficult to insert into the groove 6a formed in the side surface 6 of the cavity recess 4 is small. And the remaining resin amount remaining on the cavity side surface 6 can be reduced.
On the other hand, in the conventional mold, as shown in FIGS. 6A and 6B, the cavity side surface portion 6 has a crater portion 8b (concave surface portion) whose peripheral edge portion is surrounded by a protrusion (outer ring mountain) 8a. Therefore, the volume of the mold resin 7 fitted into the crater portion 8b is increased, and a large shearing force is required to release the mold resin in the arrow direction in the figure. Even if the mold can be released, chipping 7b occurs in the mold resin 7, or the amount of resin (resin dirt) 7c remaining in the cavity recess 4 of the mold die increases, so that maintenance is frequently performed. There is a need.

Next, another example of the processing process of the cavity recess 4 will be described. In FIG. 7A, after the cavity recess 4 is subjected to electric discharge machining so as to have a desired surface roughness and surface property, a laser beam (CO ₂ ) is used using a known laser processing machine in FIG. 7B. A gas laser, a YAG laser, etc.) are irradiated on the cavity side surface portion 6 to adjust the light intensity and irradiation time so that the surface roughness is smaller than the cavity bottom surface portion 5 where the inverse crater portion 6b is connected. Good (see FIGS. 5A and 5B).

  Further, in FIG. 8, after the cavity recess 4 is subjected to electric discharge machining so as to have a top finish or a precision finish, the cavity recess 4 is covered with a mask 10 and various chemical compositions of various compositions are formed in the cavity recess 4. The polishing liquid 9a is filled. Thus, the cavity side surface portion 6 may be subjected to chemical polishing to form a smooth surface having a smaller surface roughness than the cavity bottom surface portion 5 where the inverse crater portion 6b is continuous. In the chemical polishing, since the mold surface part is eluted evenly, the pointed part disappears first, but since the cavity bottom part 5 is also eluted simultaneously, it is suitable for smoothing the entire surface of the cavity recess 4.

  Alternatively, the cavity concave portion 4 is filled with a specific electrolytic polishing liquid 9b, so that the cavity concave portion 4 is exposed to the electrolytic polishing liquid 8 so that the surface roughness is smaller than the cavity bottom surface portion 5 where the reverse crater portion 6b is continuous. You may make it finish. In the electropolishing, if the die surface has a sharp part, a larger amount of current flows than the flat part, so that it is selectively melted quickly. Therefore, the depth of the electric discharge burr and cavity side surface part 6 is about 20 μm. It is suitable for smoothing a processing step caused by digging. Electropolishing is effective because it has higher controllability than chemical polishing.

In any processing process, the surface property of the cavity recess 4 after processing is improved as shown in FIG. Namely, cavities 4, cavity surface containing at least the cavity side part 6, an internal peripheral edge portion is surrounded by the groove 6a is formed in the continuous surface opposite crater portion 6b that protrudes are continuous (microfabricated surface R) The As a result, when the substrate 11 is clamped with the mold 1 and sealed with resin, the volume of the mold resin that bites into the cavity side surface portion 6 is reduced, so that the mold releasability is improved.
Conventionally, in FIG. 9B, the cavity concave portion 4 is a continuous surface in which a cavity surface including at least the cavity side surface portion 6 is continuous with a crater portion 8b (concave surface portion) surrounded by a protrusion (outer ring mountain) 8a. It was. Therefore, since the volume of the mold resin 7 that bites into the cavity side surface portion 6 increases, a large shearing force is required to release the mold, and the package may be chipped.

It is a section explanatory view of rough electric discharge machining between an electrode and a work. It is sectional explanatory drawing of the fine electrical discharge machining between an electrode and a workpiece | work. It is process explanatory drawing of the electrical discharge machining between an electrode and a workpiece | work. It is the elements on larger scale of the cavity side part after a process, arrow AA sectional drawing, and arrow BB sectional drawing. It is a fragmentary sectional explanatory view showing the state where mold resin is released from a cavity crevice. It is a fragmentary sectional view showing the state where the conventional mold resin is released from the cavity recess. It is process explanatory drawing which used together the laser processing which concerns on another example. It is process explanatory drawing which used together the chemical polishing process (or electrolytic polishing process) which concerns on another example. It is a schematic cross section of the metal mold | die which shows the surface property of the cavity recessed part after a process.

Explanation of symbols

W Work G Gap 1 Mold
2 Discharge electrode 3 Processing fluid
4 cavity recess
5 Cavity bottom
6 Cavity side
6a Groove 6b Reverse crater 8a Protrusion 8b Crater 7 Mold resin 9a Chemical polishing liquid 9b Electropolishing liquid 10 Mask 11 Substrate

Claims (7)

A mold that clamps a workpiece carried in alignment with a cavity recess, is filled with a sealing resin in the cavity recess, and the workpiece is resin-sealed,
Among the cavity recesses formed through the machining process including electric discharge machining on the mold base material, the surface roughness of the bottom surface of the cavity is 2.5 (Ra) to 1.5 (centerline average roughness (Ra)). The side surface portion of the cavity surrounding the range of Ra) is subjected to secondary electric discharge machining with different machining conditions, and the surface roughness is 0.5 (μRa) in terms of centerline average roughness (Ra). The cross-sectional shape of the cavity side surface portion is in a range of ~ 0.3 (μRa), the peripheral portion is surrounded by a groove portion, and a convex surface portion having a convex inside is formed on a smooth surface connected through the groove portion, and the groove portion A mold die for reducing the shearing force when releasing the molded product from the cavity recess by reducing the amount of resin remaining in the mold. 2. The mold according to claim 1, wherein the cavity side surface portion is formed on a smooth surface having a surface roughness smaller than that of the cavity bottom surface portion by laser processing instead of the secondary electric discharge machining . 2. The mold according to claim 1, wherein the cavity side surface portion is formed on a smooth surface having a surface roughness smaller than that of the cavity bottom surface portion by performing chemical polishing instead of the secondary electric discharge machining . A method of manufacturing a mold for clamping a work carried in alignment with a cavity recess, filling a sealing resin into the cavity recess, and sealing the work with a resin,
The discharge electrode matched to the machining shape of the workpiece is immersed in an insulating working fluid to perform primary electric discharge machining, and the cavity bottom surface portion of the cavity recess and the cavity side surface surrounding the cavity bottom surface portion are centerline average roughness ( Forming the cavity recess so as to have a surface roughness in the range of 2.5 (Ra) to 1.5 (Ra) at Ra) ;
Secondary discharge machining is performed by narrowing the gap of the discharge electrode with respect to the cavity side surface surrounding the cavity bottom , and the surface roughness is 0.5 (μRa) to 0.3 (centerline average roughness (Ra)). μRa) range, the cross-sectional shape of the cavity side surface portion includes a step of forming a convex surface portion having a convex inner periphery surrounded by the groove portion, and a smooth surface continuous through the groove portion,
A method for producing a mold for reducing a shearing force when releasing a molded product from the cavity recess by reducing a residual resin amount remaining in the groove . Instead of the secondary electric discharge machining, the cavity side surface portion is subjected to laser processing, and a convex surface portion in which the inside surrounded by the groove portion is convex has a smooth surface having a smaller surface roughness than the cavity bottom surface portion connected via the groove portion. The method for producing a mold according to claim 4 , comprising a forming step. Instead of the secondary electric discharge machining, the side surface of the cavity is subjected to chemical polishing, and the convex surface with the convex portion surrounded by the groove is smoother and has a smaller surface roughness than the bottom surface of the cavity connected through the groove. The manufacturing method of the mold die of Claim 4 including the process of forming. Instead of the secondary electric discharge machining, the cavity side surface portion is subjected to electropolishing processing, and the convex surface portion in which the inside surrounded by the groove portion is convex is smaller in surface roughness than the cavity bottom surface portion connected via the groove portion. The manufacturing method of the mold die of Claim 4 including the process of forming.

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