JP2008302566A - Compression molding die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent detection of abnormality at an early stage and consecutive production of defective products by adding a fail-safe mechanism with a simple configuration and high accuracy. <P>SOLUTION: The compression molding die includes: an upper die 10 supplied with a substrate 5; and a lower die 20 arranged opposite to the upper die 10 and comprising a frame-like die 23 and a plurality of compression dies 24 respectively fitted to a plurality of penetration holes 23A provided for the frame-like die 23 and capable of advancing to and retreating from the upper die 10. The plurality of compression dies 24 are connected to a single lower part die set 40 via elastic mechanisms 21 respectively independent for the respective compression dies. The elastic mechanism 21 comprises a post 21B erected on the lower part die set 40 and a beam 21A supported by the post 21B. Arranging the compression die 24 on the beam 21A makes it possible to displace a position of the compression die 24 to the lower part die set 40 to the independently advancing/retreating direction. Further, a strain gage 50 is stuck to the beam 21A so as to detect a displacement amount of each compression die. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technical field of a resin sealing device that compresses and seals a substrate or a lead frame on which a semiconductor chip is mounted with resin.

  Conventionally, as described in Patent Document 1, after a sealing material such as a thermosetting resin is put into each cavity formed by combining an upper mold and a lower mold, a substrate or a lead frame or the like is molded 2. Description of the Related Art Resin sealing devices that perform resin sealing by compression molding by placing a plurality of semiconductor chips (mounting materials) mounted on a product and applying pressure to each cavity are known.

  In this way, when a plurality of semiconductor chips are resin-sealed by a single compression molding, the resin sealing device applies a uniform sealing pressure to each cavity, but the sealing material put into the cavity Or variations in volume on the molded product side (variation of semiconductor chips, loss of passive components, etc.) causes variations in sealing pressure between the cavities.

  As a method for solving this problem, in the resin sealing device described in Patent Document 1, a plurality of cavities are connected by flow paths (runners) through which resin can freely flow, so The sealing pressure is made uniform (Patent Document 1, Paragraph 0010), and cavity blocks (compression molds) that apply pressure to each cavity are made independent, and each cavity block is further separated by an independent coil spring. There is also known a resin sealing device in which variation in sealing pressure applied to each cavity is suppressed by supporting (Patent Document 1, Paragraph 0011).

  On the other hand, as described in Patent Document 2, there is also known an apparatus for sequentially resin-sealing one semiconductor chip instead of resin-sealing a plurality of semiconductor chips at a time.

JP 2003-133350 A JP-A-9-187831

  However, even when trying to connect the cavities with flow paths (runners) through which resin can flow, slits are often provided between the semiconductor chips or the like disposed on the substrate or the lead frame, so that the flow is easy. Road (runner) may not be set. Further, the slit is mainly intended to relieve stress due to contraction of each molding block, and connecting them may distort the entire molded product such as a substrate and a lead frame.

  In addition, the original advantage of compression molding is to “suppress the flow of resin injected into the cavity and minimize the influence on the internal structure of the bonding wire”. On the other hand, the flow of the resin is induced, and there is a possibility of adversely affecting the internal structure (for example, cutting of a bonding wire, short circuit). In addition, depending on the viscosity of the resin, a pressure difference exceeding the allowable range may remain between the cavities due to pressure loss when passing through the connected flow paths.

  Moreover, in a resin sealing device in which independent compression molds for applying pressure to each cavity are supported by coil springs, the compression molds are moved up and down independently to seal between the cavities. The pressure difference can be absorbed. However, in order to maintain the thickness accuracy of the molded product after resin sealing, it is necessary to move it up and down while maintaining the flatness of the pressing surface (cavity surface) of the compression mold. Is required separately. Further, when the area of the pressing surface in the compression mold becomes larger than a certain level, a single coil spring may not be able to cover the burden, and a plurality of coil springs may be required. In such a case, even if it is difficult to evenly and accurately align the load and spring constant of each spring even for one compression mold, if there are multiple compression molds, More difficult.

  Furthermore, in the case of resin-sealing for each semiconductor chip described in Patent Document 2, it is necessary to perform compression molding a plurality of times to resin-encapsulate one substrate or lead frame. , Production efficiency is bad.

  The applicant has already proposed an invention that solves these problems (Japanese Patent Application No. 2005-353916: not known at the time of filing). Here, by supporting each of the plurality of compression molds with so-called “beams”, it is possible to relieve the sealing pressure difference between the compression molds and simultaneously support the compression molds with high accuracy. Although the occurrence of the sealing abnormality itself is greatly reduced by this proposed invention, an abnormal situation exceeding the assumed range sometimes occurs. That is, although the sealing pressure difference generated between the cavities can be eliminated by the elastic mechanism using the beam, a pressure difference that cannot be eliminated even by the elastic mechanism is generated, or some abnormality ( For example, the beam itself bends when a load exceeding the yield point is applied to the beam, or the sliding resistance of the compression mold against the frame mold is excessive, and the original sealing pressure cannot be generated. It is not always possible to deal with abnormal situations.

  Therefore, the present invention is a further improvement of the proposed invention, and it is an object to add a highly accurate fail-safe mechanism with a simple configuration to prevent early abnormality detection and continuous production of defective products. It is what.

  The present invention provides a first mold to which a product to be molded is supplied, and a frame-shaped mold and a plurality of through holes provided in the frame-shaped mold, which are arranged to face the first mold. A compression mold including a second mold having a plurality of compression molds capable of moving forward and backward with respect to the first mold while being fitted, wherein the plurality of compression molds are Each compression mold is connected to a single plate member via an independent elastic mechanism, and the elastic mechanism has a column portion standing on the plate member and a beam portion supported by the column portion. By disposing the compression mold in the beam portion, the position of the compression mold with respect to the plate member can be displaced independently in the advancing and retreating direction, and the amount of displacement is further changed for each compression mold. The above-described problem is solved by providing a detecting means capable of detecting the above.

  By adopting such a configuration, when pressure exceeding the allowable range is generated for each compression mold, abnormalities such as an abnormality in the elastic mechanism itself, an increase in the sliding resistance of the compression mold relative to the frame mold, etc. Can be detected early and reliably. For example, if the displacement detected by the detection means exceeds a predetermined range, the advance / retreat is stopped and a predetermined notification process is performed, so that continuous production of defective products can be prevented.

  Specifically, if the detection means is configured to have a strain gauge affixed to the beam portion and a Wheatstone bridge circuit connected to the strain gauge, the design change of the mold that has already been proposed can be made. The detection means can be configured without necessity.

  In this case, a plurality of strain gauges are affixed to the beam portion, and at least one of the strain gauges is estimated based on a position where no strain is generated even by the displacement or a measurement value of another strain gauge. If it is configured to be attached at a possible position, temperature correction of a strain gauge that is easily affected by temperature becomes possible, and an improvement in accuracy can be expected. That is, some strain gauges of a plurality of strain gauges (resultingly) are used only for detecting temperature changes, so that other strain gauges are detecting strain (ie, displacement) of the beam portion. It is possible to correct the temperature for the detected result.

  Further, if the detection means is constituted by a position displacement meter, it becomes easy to obtain a stable detection result without requiring correction due to the difference in the attachment position as in a strain gauge.

  Further, if the detecting means is configured so that the displacement amount can be calculated as the pressing force of the compression mold, the abnormality detection can be managed based on the pressing force of the compression mold, that is, the pressure base generated in each cavity. It becomes possible.

  By applying the present invention, it becomes possible to prevent the occurrence of a sealing pressure difference occurring between the cavities, and it is possible to provide a fail-safe in case of an abnormal situation.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of a compression molding die to which the present invention is applied, in which (A) is a front view and (B) is a side view.

<Composition of compression mold>
The upper mold (first mold) 10 according to the present embodiment can hold the substrate (molded product) 5 by suction at a predetermined timing. Here, a substrate is described as an example, but the same applies to a lead frame, for example. Although not shown, a plurality of semiconductor chips (mounting materials) are arranged on the substrate 5. Further, the upper die 10 is supported and fixed by an upper die set 30 located on the upper portion of the upper die 10. Further, the upper die set 30 is provided with a heater 30H, and the temperature is controlled so that a predetermined temperature can be maintained (for example, 175 degrees).

  On the other hand, a lower mold (second mold) 20 having a frame-shaped mold 23 and a compression mold 24 is disposed so as to face the upper mold 10. The compression mold 24 is configured to be able to advance and retreat (advance and retreat with respect to the upper mold 10: up and down movement in this case) while fitting into a plurality of through holes 23 </ b> A provided in the frame-shaped mold 23. A cavity 32 is formed by being surrounded by the upper mold 10 and the lower mold 20 (the frame-shaped mold 23 and the compression mold 24) described above.

  The compression mold 24 is connected and fixed to a lower die set (plate member) 40 via an elastic mechanism 21 having a beam portion 21A and a column portion 21B. The frame-shaped mold 23 is supported from the lower die set 40 via a coil spring (not shown), and is configured to be movable up and down independently. The lower die set 40 also has a built-in heater 40H and is temperature controlled so that a predetermined temperature can be maintained.

  Although not shown, the lower die set (plate member) 40 is supported by a press mechanism (not shown) or the like, and the entire lower die 20 can be opened and closed with respect to the upper die 10 at a predetermined timing. It is said that. Further, for example, a load cell is disposed between the press mechanism and the lower die set 40 to detect the pressure generated by the press mechanism.

  The elastic mechanism 21 is configured to have a column portion 21B standing on the lower die set 40 and a beam portion 21A hung so as to connect the column portion 21B. In the present embodiment, the beam portion 21A and the column portion 21B are configured as separate members, but may be configured integrally. As a result of this configuration, a gap portion 21C is formed immediately below the beam portion 21A, the beam portion 21A is allowed to bend due to the presence of the gap portion 21C, and can function as the elastic mechanism 21. Has been. In addition, at least the beam portion 21A in the elastic mechanism 21 is formed of a member (for example, iron or the like) that can be processed with high accuracy.

  The compression mold 24 is placed at substantially the center of the beam portion 21A, and both ends of the beam portion 21A are supported from the lower die set (plate member) 40 side by the column portions 21B. That is, it is arranged and configured to function as a “both supported beam”. As described above, since the compression mold 24 is placed on the beam portion 21A formed of a member that can be processed with high accuracy, the compression portion 24A is compressed by giving the beam portion 21A sufficient strength at the time of design. It is not necessary to provide a separate guide mechanism in preparation for the displacement of the mold 24.

  Further, as shown in FIG. 1B, when the mold is viewed from the side, independent compression molds 24 are fitted in the plurality of through holes 23A provided in the frame-shaped mold 23, respectively. It is arranged to be able to move forward and backward. Each of the compression molds 24 is placed on the beam portion 21A of the independent elastic mechanism 21 in the same manner as described above. Although the elastic mechanism 21 in the present embodiment has a completely independent configuration, for example, in addition to this, the column portions 21B may be integrally formed, and only the beam portion 21A may be independent. That is, it can be said that it is an “independent elastic mechanism” as long as the beam portion 21A corresponding to each compression mold 24 can be bent independently. With such a configuration, one of the plurality of compression molds 24 is not affected by the reaction force of the sealing pressure received by the other compression molds 24 through the beam portion 21A.

  Further, a strain gauge 50 is affixed in the vicinity of the mounting position of the compression mold 24 in the beam portion 21A. In the present embodiment, the strain gauge 50 is affixed to the upper surface side of the beam portion 21A. However, the strain gauge 50 is not limited to this location, and “when the cavity 32 is compressed by the compression mold 24 in the beam portion 21A. As long as it is the “position where distortion occurs”, it can be placed anywhere. In the present embodiment, only one strain gauge 50 is attached, but a configuration in which a plurality of strain gauges are attached and the average value of each gauge is taken to increase detection accuracy may be employed. .

  Further, since the strain gauge 50 changes its own resistance value due to the occurrence of strain, a Wheatstone bridge circuit 60 for taking out the changing resistance value as a change in voltage is connected. The Wheatstone bridge circuit 60 is connected to the calculation unit 80 and the control unit 90 via an amplifier 70 for amplifying its own output signal.

  The calculation unit 80 converts the electrical signal output from the strain gauge 50 and the Wheatstone bridge circuit 60 as detection means into a displacement amount (amount of deflection of the beam portion 21A = a displacement amount of the lower die set 40 of the compression mold 24). It is possible to convert. For example, an output value (an output value from the Wheatstone circuit 60) with respect to a known displacement amount is stored in advance as known information, and the displacement amount can be detected by comparing with the stored information. Further, if it is made to correspond to a known pressure (pressure generated in the cavity 32 = pressure generated on the pressing surface 24A of the compression mold 24), management based on an allowable pressure base for each product can be performed. In addition, the control unit 90 can set and store the allowable range of the displacement amount and the pressure in advance, and if the calculation result by the calculation unit 80 exceeds the range, a predetermined value is stored. It is possible to perform processing (for example, stopping the advance and retreat of the lower mold 20, lighting a warning lamp, generating a warning sound, etc.).

<Operation of compression mold>
A substrate (molded product) 5 to be sealed with resin is supplied to the upper mold 10 by a supply mechanism (not shown), and is sucked and held by the upper mold 10. On the other hand, resin as a sealant is supplied to the lower mold 20 side by a supply mechanism (not shown). The resin supplied here may be a molten resin (liquid resin) that has already melted at the time of supply, or a resin that is not yet melted, such as a chip, powder, granule, or plate. It may be. If it is not yet melted at the time of supply, it is melted by the heater.

  Thereafter, a press mechanism (not shown) is operated so that the frame-shaped mold 23 comes into contact with the upper mold 10. Even after the frame-shaped mold 23 comes into contact with the upper mold 10, the compression mold 24 further moves in the through-hole 23 </ b> A of the frame-shaped mold 23 by operating a press mechanism (not shown). Proceed toward the 10th side. By this operation, the charged resin seals the semiconductor chip while compressing it. The press is stopped when a set load of the press mechanism (for example, detected by a load cell disposed between the press mechanism and the lower die set 40) is reached.

  On the other hand, in the compression molding die, compression molding is performed simultaneously in the plurality of cavities 32 by the plurality of compression dies 24 in one press operation. Therefore, there is a possibility that a sealing pressure difference may occur on the pressing surface 24A of each compression mold 24 depending on the amount of resin put into each cavity 32 and the volume of the molded product itself supplied to each cavity 32. . That is, when the original volume of each cavity 32 is uniform and the sealing pressure of the press mechanism is evenly distributed to each compression mold 24, the amount of sealing material put into one of the cavities Is larger than the other cavities 32, or when the volume of the molding itself placed in one cavity 32 is large, even if compression molding is performed by the same pressure, In comparison, the pressure in the other cavities 32 is relatively low. As a result, the desired pressure is not reached, resulting in molding defects such as voids remaining.

  However, in the compression mold according to the present embodiment, each compression mold 24 is supported by the elastic mechanism 21 as described above. This elastic mechanism 21 has a structure in which a compression mold 24 is placed at a substantially central portion of the beam portion 21A, and is supported by a column portion 21B from a lower die set (plate member) 40 at both end portions of the beam portion 21A. Therefore, when a reaction force due to sealing is applied to the pressing surface 24A of the compression mold 24, the beam portion 21A is bent to absorb this pressure. That is, even when a pressure difference is generated on the pressing surface 24A of each compression mold 24 due to, for example, a difference in the amount of resin charged, each beam portion 21A is bent by a necessary amount so that the pressure difference is within an allowable range. Can be absorbed.

  For example, when the specific gravity of the resin to be input is 2, the accuracy of the resin amount to be input to each cavity 32 is about ± 50 mg, and the size of the sealing portion (that is, the size of the cavity 32) is 40 mm × 60 mm The thickness error of the sealing portion based on the resin amount error is about ± 0.01 mm.

  In the present embodiment, pressure (applied to the compression mold 24) is calculated from the second moment of section due to the cross-sectional shape of the beam portion 21A of the elastic mechanism 21, the longitudinal elastic modulus that is the material characteristic of the elastic mechanism 21, and the length of the beam portion 21A. Since the beam portion 21A is designed so that the beam portion 21A has a deflection amount of 0.2 mm with respect to 10 MPa (sealing reaction force), for example, the thickness of the 0.01 mm sealing portion is changed. However, the sealing pressure applied to the pressing surface 24A of the compression mold 24 increases only by about 0.5 MPa in addition to the original sealing pressure. If the sealing pressure changes to this extent, there will be no molding failure.

  Of course, the above-mentioned numerical value shows an example and is not limited to the numerical value. It can be changed as appropriate depending on the type and material of the molded product to be sealed, and the type of resin as the sealing material. However, in order to exert pressure equalization by the mechanism of the present proposal, it is preferable to set the material and shape of the beam portion so that the above-described deflection amount is 100 MPa / mm or less.

  Furthermore, in the present embodiment, a strain gauge 50 is attached to the beam portion 21A, and the degree of strain of the beam portion 21A, that is, the amount of displacement of the compression mold 24 is detected. Therefore, in the unlikely event that a pressure difference that cannot be resolved by the elastic mechanism 21 occurs, or the elastic mechanism 21 itself is subjected to some abnormality (for example, the beam 21A itself is bent due to a load exceeding the yield point). The press mechanism is immediately stopped even if an abnormal situation occurs, such as when the compression die 24 slides excessively on the frame die 23 and the original sealing pressure cannot be generated. It is possible to make it. As a result, defective products are not continuously produced.

  Although not shown in the drawing, based on a position where no distortion occurs (for example, a position on the opposite side of the mounting position of the compression mold 24 in the beam portion 21A) or a measured value of the strain gauge 50 attached to the beam portion 21A. Therefore, if a strain gauge of the same type is separately attached at a position where the relative strain level can be estimated, the detection accuracy can be improved.

  The mold may be equipped with a heater and is always in an environment where temperature changes can occur. Since the resistance value of the strain gauge changes due to the temperature change of the mold, it is necessary to perform temperature correction in order to detect an accurate value. Therefore, if a strain gauge of the same type is separately attached to, for example, “a position where no strain is generated even when the compression mold moves back and forth in the sealing process”, the resistance value of the strain gauge changes only with temperature changes. It becomes. By using this changed value as the correction value, it is possible to improve the accuracy of the detection result of the original strain gauge that detects the strain (that is, the displacement amount) of the beam portion.

  In addition, as a secondary effect, it is possible to detect an abnormality in the load cell arranged separately. That is, the load cell abnormality can be detected by associating the detection result of the load cell in the normal state with the detection result of the detection means.

  Next, an example of another embodiment will be described with reference to FIG.

  In addition, about the part which is the same as that of the compression molding die demonstrated using FIG. 1, or only the last 2 digits of a number attaches | subjects the same code | symbol, description of the overlapping structure and description of an effect | action are abbreviate | omitted.

  FIG. 2 is a front view showing a compression mold showing an example of another embodiment according to the present invention.

  In the other embodiment in FIG. 2, the difference from the compression mold in the first embodiment is that the deflection of the beam portion 121A by the displacement meter 151 embedded in the lower die set 140, that is, the compression mold 124 is used. The amount of displacement with respect to the lower die set 140 is directly detected. In the case of a strain gauge, it is necessary to correct each time depending on the place where the gauge is attached. However, when the displacement meter 151 is used, such correction is unnecessary and it is easy to obtain a stable detection result. Become. The displacement meter 151 can employ various methods such as an overcurrent method, an optical method, an ultrasonic method, a laser focus method, and a contact method. Of course, even in the case of the present embodiment, it is possible to detect an abnormality for each compression mold as described above.

  In addition, although it is common in all the above-mentioned embodiments, the material of the beam portion does not necessarily need to be a single material. For example, different materials may be laminated to form a specific amount of bending. Good. Further, the shape may not be a single shape, and for example, it may be set to become thinner (or thicker) as it approaches the portion where the compression mold is placed. Of course, these may be combined. As described above, the design of the deflection amount can be realized by various approaches.

  Further, in the description of the above-described embodiment, the support column part constituting the “elastic mechanism” is configured as a member different from the lower die set. However, in the elastic mechanism according to the present invention, it is not an essential requirement that the strut portion and the lower die set are formed of one member. For example, it is possible to adopt a configuration in which the shape of the lower die set is changed to form the column part integrally with the lower die set, and the beam part made of another member is supported on the column part.

  In addition, in the above description, the column portion in the so-called “both-end supported beam structure” is positioned at the end portion of the beam portion, but the configuration in which the column portion is positioned other than the end portion (for example, the column portion with respect to the beam portion). It is good also as a structure which has a mechanism which can be moved and fixed to a horizontal direction. It is possible to adjust the amount of bending also by changing the position of the column in this way.

  For example, it is suitable as a mold for a resin sealing device in which a molded product having a plurality of semiconductor chips mounted on one substrate or lead frame is compression-molded at a time by one press mechanism.

It is a figure which shows the structure of the compression mold which shows an example of embodiment of this invention, Comprising: (A) is a front view, (B) is a side view. Front view of compression molding mold showing an example of another embodiment (second embodiment) of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 ... Board | substrate 10 ... Upper metal mold | die 20 ... Lower metal mold | die 21 ... Elastic mechanism 21A ... Beam part 21B ... Column part 21C ... Space | gap part 23 ... Frame-shaped metal mold 23A ... Through-hole 24 ... Compression mold 24A ... Pressing surface 30 ... Upper die set 32 ... Cavity 40 ... Lower die set 50 ... Strain gauge 60 ... Wheatstone bridge circuit 70 ... Amplifier 80 ... Calculation unit 90 ... Control unit

Claims (6)

A first mold to which a product to be molded is supplied, and a first mold that is disposed opposite to the first mold, and are respectively fitted into a frame-shaped mold and a plurality of through holes provided in the frame-shaped mold. A compression mold having a second mold having a plurality of compression molds movable forward and backward with respect to the first mold,
The plurality of compression molds are connected to a single plate member via an independent elastic mechanism for each compression mold,
The elastic mechanism has a column part standing on the plate member and a beam part supported by the column part,
By disposing the compression mold on the beam portion, the position of the compression mold with respect to the plate member can be independently displaced in the advancing and retracting direction,
Furthermore, the compression molding die characterized by including the detection means which can detect this displacement amount for every said compression die. In claim 1,
The compression molding die, wherein when the displacement detected by the detecting means exceeds a predetermined range, the advance / retreat is stopped and a predetermined notification process is performed. In claim 1 or 2,
The compression molding die, wherein the detecting means includes a strain gauge attached to the beam portion and a Wheatstone bridge circuit connected to the strain gauge. In claim 3,
A plurality of the strain gauges are affixed to the beam part, and at least one of the strain gauges is a position where no strain is generated even by the displacement or a position where the degree of strain can be estimated based on the measurement value of another strain gauge. A compression mold characterized by being affixed. In claim 1 or 2,
The compression molding die, wherein the detection means is a position displacement meter. In any of claims 3 to 5,
The detection means can further calculate the displacement amount to the pressing force of the compression mold. A compression mold.

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