JP4042430B2 - Method and apparatus for detecting mold release force of molded product - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting a release force from a mold of a molded product obtained by molding a raw material such as a thermosetting resin in a mold, and a mold release force detecting device for the molded product used in the detection method. .
[0002]
[Prior art]
FIG. 1 shows a general molding die and a data collection / analysis apparatus for manufacturing a molded product by thermoforming raw materials. In FIG. 1, the molding die is shown by a schematic cross-sectional view. FIG. 2 is a schematic cross-sectional view showing an example of a mold release state in the vicinity of a molded product in the mold shown in FIG. In the molding die 1, a raw material such as molten resin is cast into a molding cavity 9 between the upper die 2 and the lower die 3. After the raw material is heated and cured in the cavity, the mold is opened, and at the same time, the mold is released from the upper mold cavity by the upper ejector pin 12, and the molded product is held in the lower mold cavity. Next, as shown in FIG. 2, the mold is released from the lower mold cavity by the lower mold ejector pin 12 'to complete the molding.
If an excessive force is applied to the molded product at the time of mold release, for example, in the case of a semiconductor package, the internal chip cracks or peels off from the resin, causing problems that impair the function and reliability of the semiconductor product. Evaluation of mold release force is important.
The measurement of the mold release force of the resin molded product according to the prior art is referred to as an end of the lower mold ejector pin 12 ′ provided in the cavity 9 that is not in contact with the molded product 18 (hereinafter referred to as the other end). ) Was provided with a load meter 15. As shown in FIG. 2, the load applied to the ejector pin is detected by the load meter during the mold release operation in which the molded product 18 is released from the lower mold cavity by the ejector pin 12 '. The maximum value of the load was taken as the mold release force applied to the molded product.
[0003]
[Problems to be solved by the invention]
However, when the raw material is a resin, particularly a thermosetting resin, the viscosity is about an order of magnitude smaller than that of the thermoplastic resin. FIG. 3 shows a schematic view of the burr generation situation around the ejector pin of the molding die. However, only the eject pin 12 'is a side view. As shown in FIG. 3, in the case of a resin having a particularly low viscosity, the resin enters the clearance (clearance) 20 between the ejector pin 12 'and its sliding hole 19 during molding, and this resin is placed around the ejector pin 12'. As a result, the burr 21 is cured. This burr causes a large sliding resistance of the ejector pin, and there is a problem that a force larger than the force (load) applied to the molded product is transmitted to the load meter and the effective release force cannot be detected.
Here, the effective release force is defined as a force (load) applied to the molded product in order to release the molded product.
[0004]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the inventors of the present invention have a load profile applied to an ejector pin at the time of mold release and a load at the time of an air mold release operation of the ejector pin that is not accompanied by mold release. Focusing on obtaining an effective release force of the molded product by detecting the profile, that is, the sliding resistance load of the ejector pin, and canceling out the sliding resistance load, the present invention has been achieved.
[0005]
That is, the first detection method in the present invention is:
Detecting the load applied to the ejector pin by the operation of releasing the molded product by sliding the ejector pin in the molding die and outputting it as a first load signal;
Collecting and analyzing the first load signal to detect a release load profile (F1);
A step of detecting a load applied to the ejector pin by an operation in which the ejector pin slides empty after the molded product is released, and outputs the second load signal, and collects and analyzes the second load signal. A step of detecting a separation load profile (F2) corresponding to the ejector pin sliding resistance;
A step of obtaining an effective mold release force applied to the molded product by subtracting the air release mold load profile (F2) from the mold release load profile (F1). This is a detection method.
[0006]
The second detection method in the present invention is a step of detecting a load applied to the ejector pin by an operation of releasing the molded product by sliding the ejector pin in the molding die and outputting it as a load signal;
Collecting and analyzing the load signal to detect a release load profile (F1);
Estimating the load of the sliding resistance (F2 ′) of the ejector pin based on the release load profile (F1);
A step of obtaining an effective mold release force applied to the molded product by subtracting the load of the estimated sliding resistance (F2 ′) from the mold release load profile (F1). This is a mold release force detection method.
[0007]
The first detection device in the present invention detects the load applied to the ejector pin by the operation of releasing the molded product by sliding the ejector pin in the molding die, and outputs it as a first load signal. Means for detecting a load applied to the ejector pin by an operation in which the ejector pin slides empty after the molded product is released and outputs it as a second load signal;
Means for collecting and analyzing the load signal and detecting the release load profile (F1) from the first load signal and the release load profile (F2) corresponding to the ejector pin sliding resistance from the second load signal. When,
A mold release force for the molded product comprising means for obtaining an effective mold release force loaded on the molded product by subtracting the air release mold load profile (F2) from the mold release load profile (F1). It is a detection device.
[0008]
The second detection device in the present invention is a means for detecting the load applied to the ejector pin by the operation of releasing the molded product by sliding the ejector pin in the molding die and outputting it as a load signal;
Means for collecting and analyzing the load signal to detect a release load profile (F1);
Means for estimating the load of the sliding resistance (F2 ′) of the ejector pin based on the release load profile (F1);
A molded product comprising means for obtaining an effective mold release force loaded on the molded product by subtracting the estimated sliding resistance (F2 ′) load from the mold release load profile (F1). This is a release force detecting device.
The load of the sliding resistance (F2 ′) of the ejector pin is estimated by interpolating an approximate expression between the point at which effective release is started and the point at which release is completed into the release load profile F1. preferable.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment according to the present invention will be described with reference to the drawings. In this aspect, a method and an apparatus for detecting an effective mold release force for molding a semiconductor package using an epoxy resin for semiconductor encapsulation will be described. The effective mold release force is defined as a force (load) applied to the molded product in order to release the molded product.
[0010]
First, the structure of the molding die and the process from molding to mold release will be briefly described with reference to FIGS. The molding die 1 is a multi-pot molding die for molding a resin-encapsulated semiconductor package 18. The molding die 1 has an upper mold 2 and a lower mold 3, and although not shown, operations such as heating conditions and mold release start can be set by a molding condition setting unit of a molding apparatus.
[0011]
The potting 4 provided in the center of the lower mold 3 is charged with a semiconductor sealing epoxy resin 6 tableted in a tablet shape. The molding die is heated to around 180 ° C., and the molten resin is cast into the molding cavity 9 via the runner 7 and the gate 8 by the upward movement of the plunger 5. A lead frame 11 on which a semiconductor chip 10 is mounted is set in the cavity 9 in advance, and the semiconductor chip 10 is molded and sealed with the resin.
The upper and lower ejector plates 13, 13 ′ 14, 14 ′ are moved by ejector rods (not shown) built in the molding die. After the sealing resin is heat-cured, the lower mold 3 is operated downward to open the mold, and at the same time, the upper mold ejector plates 13 and 14 are first operated downward, whereby the upper mold ejector pin 12 is moved. The mold is slid and released from the cavity of the upper mold 2. The semiconductor package 18 which is a molded product is held in the cavity of the lower mold 3.
Thereafter, as shown in FIG. 2, the lower mold ejector plates 13 'and 14' are moved upward and the lower mold ejector pin 12 'slides to release the molded product from the lower mold cavity. Is completed.
[0012]
In order to detect the release force of the molded semiconductor package 18, the detection device of the present invention first has means for detecting a load applied to the ejector pin and outputting it as a load signal. An example of this means is a load meter, and a load meter 15 (for example, a crystal piezoelectric load cell manufactured by Kistler) is connected to the lower ejector pin 12 'in the molding die. Due to the structure of the molding die, the load meter is provided at the other end, that is, the lower portion of the lower ejector pin 12 '.
The detection device of the present invention has means for collecting and analyzing the load signal and obtaining a load profile from the load signal. As this means, a data collection / analysis device such as an amplifier 16 or a personal computer 17 can be used.
[0013]
The first detection method and detection apparatus of the present invention will be described.
In the first detection method of the present invention, first, the load applied to the ejector pin is detected by the operation of releasing the molded product (for example, a semiconductor package) by sliding the lower mold ejector pin. Output as a load signal.
Specifically, the operation of releasing the molded product is performed by releasing a semiconductor package molded product that has been cured in the mold 1 from a state in which the upper mold is removed, under a predetermined mold release speed (lower mold ejector pin 12 2), the mold is released at the sliding distance of the ejector pin 12 'to reach the state shown in FIG. This operation is hereinafter referred to as a molded product release operation.
[0014]
The first load signal is then collected and analyzed to obtain a release load profile. That is, the load signal output from the load meter is taken into a collection / analysis device such as a personal computer 17 through the amplifier 16, and load data is collected and analyzed by the device.
The load signal from the load cell 15 is preferably loaded into the personal computer 17 as a function of time at a time interval of at least 500 microseconds (μs) in order to clarify the release behavior.
The load meter 15 senses the filling pressure in the resin filling process in addition to the mold release load of the molded product. Therefore, in order to detect only the load during the mold release operation, the load signal from the load meter is collected using the mold release operation start signal from the molding condition setting unit (not shown) as a trigger, and the collection time is It is preferable to set the mold release completion time of the molded product (semiconductor package).
FIG. 4A shows an example of a release load profile (change in release load with time) per one ejector pin (hereinafter referred to as release load profile F1) 22 obtained from the first load signal. Show.
[0015]
Subsequently, after the molded product is released, the load applied to the ejector pin by the operation of sliding the ejector pin in the sky is detected and output as a second load signal.
That is, a lower mold ejector pin is returned to the position before the mold release operation is started, and a mold release operation (hereinafter referred to as an air mold release operation) is performed in which there is no molded product. This empty mold release operation is automatically performed by setting the operation of the molding apparatus. The load at this time is detected by a load meter in the same manner as described above and output as a second load signal.
[0016]
The second load signal is collected and analyzed to obtain an isolated load profile.
In the same manner as described above, the load signal output from the load cell is taken into a collection / analysis device, and load data is collected and analyzed by the device. FIG. 4B shows an example of a release load profile (hereinafter referred to as an “release load profile F2”) 23 per ejector pin during the release operation. The air mold release load profile 23 corresponds to the load due to the sliding resistance of the ejector pin 12 ′ since the molded product has already been released by the above-described molded product release operation.
[0017]
From the release load profile shown in FIGS. 4A and 4B, the release behavior that has not been clarified in the past has been clarified. That is, (1) there is a large peak at the beginning of the ejector pin operation start (due to static friction of the ejector pin), and (2) mold release is about 22 milliseconds (ms) after the ejector pin starts operating. (3) Even after completion of mold release, it was revealed that the ejector pin was subjected to a sliding load (due to the dynamic friction of the ejector pin).
As described above, it is understood that the release load profile 22 shown in FIG. 4A is far from the effective release force.
[0018]
Therefore, the effective mold release force applied to the molded product is subtracted from the mold release load profile (F2) 23 shown in FIG. 4B from the mold release load profile (F1) 22 shown in FIG. Can be obtained.
[0019]
In the first detection device of the present invention, means for outputting the load due to the mold release operation as a first load signal, and outputting the load due to the air release operation as a second load signal;
In addition to collecting and analyzing a load signal and detecting a release load profile F1 from the first load signal and an air release load profile F2 from the second load signal,
Means for obtaining an effective mold release force loaded on the molded product by subtracting F2 from F1 is included. As a means for subtracting F2 from F1, a data collection / analysis device such as a personal computer 17 can be used, and may be the same as or different from the data collection / analysis device for detecting the release load profile.
[0020]
The result of subtracting F2 from F1 in FIG. 4 to obtain the effective release force is shown in FIG. From the effective release force (F) profile 24 shown in FIG. 5A, it can be read that the maximum release force (the maximum value of the effective release force) is 2.6 N (per ejector pin). . Incidentally, it can be seen that in the conventional method in which the mold release load is determined by only one mold release operation, the maximum mold release force is determined to be 4.9 N and does not represent the effective mold release force.
[0021]
It should be noted that the large load peak at the beginning of the operation of the ejector pin (1) described above is very low in the viscosity of a thermosetting resin such as a semiconductor-sealed epoxy resin, and therefore, as shown in FIG. The resin enters the gap (clearance) 20 between the first and second sliding holes 19 to form burrs 21, which are caused by static friction. In particular, since the semiconductor-sealed epoxy resin is filled with silica particles of several micrometers to submicrometers, wear of the ejector pins by the burr 21 proceeds. As a result, the sliding resistance increases each time the molding is repeated, and therefore the processing shown in the present invention is indispensable for obtaining an effective release force.
As described above, the effective mold release force profile can be obtained by subtracting the mold release load profile obtained by the mold release operation in the absence of the molded product from the mold release load profile obtained by the mold product release operation.
[0022]
Next, the second detection method and detection apparatus of the present invention will be described.
Examining the release load profile (F1) 22 shown in FIG. 4A and the air release load profile (F2) 23 shown in FIG. 4B, only the release load profile (F1) shown in FIG. From this, it is possible to estimate and determine the load of the separation-type load profile, that is, the load of the sliding resistance (F2 ′) of the ejector pin.
That is, the sliding resistance of the ejector pin can be estimated based on F1 by interpolating F1 with an approximate expression of the point A at which effective mold release is started and the point B at which mold release is completed. FIG. 5B shows a state in which an approximate expression based on the points A and B is inserted into F1.
In FIG. 5, from the example of FIG. 4A, an approximate expression for the sliding resistance of the ejector pin is the following expression (1).
F2 '= 2.4689 t ^-0.1367 (1)
Where F2 ′: Ejector pin sliding resistance (N), t: Time (ms)
From the time t = 12.5 ms at the load peak point P excluding the load peak immediately after the start of the ejector pin operation at F1, and the equation (1), the estimated sliding resistance (F2 ′) 25 of the P point is 1. 73N.
By subtracting the estimated load of the sliding resistance F2 ′ from the release load profile F1, an effective release force loaded on the molded product can be obtained. For example, when 1.73N is subtracted from the load 4.18N at the load peak point P of F1, an effective release force of 2.45N is obtained. This value is not much different from the maximum value 2.6N of the effective release force obtained by the first detection method.
[0023]
As described above, according to the second detection method, it is possible to estimate the sliding resistance of the ejector pin from the release load profile 22 and obtain the effective release force by subtracting the sliding resistance. it can. In addition to the means for outputting the load signal and the means for detecting the release load profile, the second detection device of the present invention detects the load of the sliding resistance F2 ′ of the ejector pin based on the release load profile F1. A means for estimating and means for subtracting the load of F2 'from F1 to obtain an effective mold release force applied to the molded product, and a data collecting / analyzing device such as a personal computer 17 can be used as the latter two means. As long as these means are included, the same device as the first detection device may be used.
In the above, the case where the raw material of the molded product is an epoxy resin has been described. However, the detection method and the detection device of the present invention are thermosetting resins other than epoxy resins, thermoplastic resins, and ceramics as long as they are molded by a molding die. Further, it can be applied to molding of powder metal, molten metal and the like.
[0024]
【Example】
Example 1
In this example, the mold and apparatus shown in FIG. 1 were prepared.
That is, in order to detect the mold release force of the molded semiconductor package, a load meter 15 (a crystal piezoelectric load cell manufactured by Kistler) was provided below the lower ejector pin 12 '. The load signal from the load meter 15 is taken into the personal computer 17 through the amplifier 16, and load data is collected and analyzed. Since the load meter 15 senses the filling pressure in the resin filling process in addition to the mold release load of the molded product, in this embodiment, the molding conditions are set so that only the load during the mold release operation can be detected. A load signal is taken into the personal computer 17 using a release operation start signal from a part (not shown) as a trigger, and the take-in time is set as the release completion time of the semiconductor package.
[0025]
A semiconductor package LQFP (20 × 20 × 1.4 mm) was molded under the conditions of a mold temperature of 180 ° C. and a molding pressure of 10 MPa using a biphenyl epoxy resin filled with 80% by volume of silica filler as a sealing resin.
The molded product of the semiconductor package cured in the mold 1 was released under the conditions of a mold release speed (speed of the ejector pin 12 ′) of 8 mm / s and a sliding distance of the ejector pin 12 ′ of 3 mm (mold release). Operation). A load signal (first load signal) from the load cell 15 was taken into the personal computer 17 as a function of time at a time interval of 500 microseconds (μs) to obtain a release load profile.
A release load profile 22 obtained from the first load signal is shown in FIG.
[0026]
Further, after the first release operation, the ejector pin 12 'was continuously returned to the position before the start of the initial release operation, and then the release operation was performed without a molded product. This operation is automatically performed according to the setting of the molding apparatus. The load at this time was collected and analyzed in the same manner as the first load signal from the second load signal detected by the load meter in the same manner as described above to obtain an air separation type load profile.
This idle load profile 23 is shown in FIG. The air release load profile 23 is a load due to the sliding resistance of the ejector pin 12 ′ because the molded product has already been released in the first release operation.
[0027]
Calculation was performed by the personal computer 17, and the effective release force was obtained by subtracting the air release load profile 23 shown in FIG. 4 (b) from the release load profile 22 shown in FIG. 4 (a).
The result is shown in FIG. From the effective mold release force (F) profile 24 shown in FIG. 5A, it was read that the maximum mold release force was 2.6 N (per ejector pin).
As described above, an effective release force profile could be obtained by subtracting the empty release load profile without the molded product from the release load profile for releasing the molded product.
[0028]
(Example 2)
From only the first release load profile 22 shown in FIG. 4A obtained in Example 1, the release load profile, that is, the sliding resistance of the ejector pin, was determined as follows.
That is, as shown in FIG. 5B, the sliding resistance of the ejector pin was estimated by interpolating a point A at which effective release was started and a point B at which release was completed by an approximate expression.
From the first release load profile 22 in FIG. 4A, the approximate expression is the following expression (1).
F2 '= 2.4689 t ^-0.1367 (1)
Where F2 ′: Ejector pin sliding resistance (N), t: Time (ms)
Thus, from time t = 12.5 ms at the load peak point P excluding the load peak immediately after the start of the ejector pin operation, F2 ′ is 1.7 N from the equation (1). When 1.7 N was subtracted from the load 4.2 N at the load peak point P, an effective release force of 2.5 N was obtained. This value was not much different from the maximum effective release force 2.6 N obtained by the method of Example 1 above.
[0029]
As described above, according to this embodiment, the effective release force can be obtained by estimating the sliding resistance of the ejector pin from the release load profile 22 and subtracting the sliding resistance.
[0030]
(Comparative example)
The same procedure as in Example 1 was performed except that the conventional method for determining the release load with the release load profile 22 from the release operation for releasing the molded product shown in FIG. The maximum release force was determined to be 4.9 N, and it was found that it did not represent the effective release force.
[0031]
【The invention's effect】
According to the present invention, the effective release force between the molding die and the molded product can be detected, and even if the sliding resistance of the eject pin increases each time the molding is repeated, the effective release force at each molding time. Can be easily detected.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a molding die and a data collection / analysis device.
2 is a schematic cross-sectional view showing an example of a mold release state in the vicinity of a molded product in the mold shown in FIG.
FIG. 3 is a schematic cross-sectional view showing a state of occurrence of burrs around an ejector pin of a molding die.
FIG. 4A shows an example of a release load profile according to the present invention.
(B) The figure which shows an example of the separation-type load profile by this invention.
5A is a diagram showing an effective release force profile according to the release load profile of FIG. 4; FIG.
(B) The figure which shows the estimation method of the ejector pin sliding resistance load by the mold release load profile of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Molding die 2 ... Upper mold 3 ... Lower mold 4 ... Pot 5 ... Plunger 6 ... Epoxy resin 7 for semiconductor sealing ... Runner 8 ... Gate 9 ... Cavity 10 ... Semiconductor chip 11 ... Lead frame 12 ... Upper mold Ejector pin 12 '... Lower ejector pins 13, 14 ... Upper ejector plate 13', 14 '... Lower ejector plate 15 ... Load meter 16 ... Amplifier 17 ... Personal computer 18 ... Semiconductor package (molded product) 19 ... Ejector pin sliding hole 20 ... Clearance 21 ... Burr 22 ... Release load profile 23 ... Air release load profile 24 ... Effective release force profile 25 ... Estimated ejector pin sliding resistance load

Claims (3)

Detecting the load applied to the ejector pin by the operation of releasing the molded product by sliding the ejector pin in the molding die and outputting as a load signal;
Collecting and analyzing the load signal to detect a release load profile (F1);
Estimating the load of the sliding resistance (F2 ′) of the ejector pin based on the release load profile (F1);
A step of obtaining an effective mold release force applied to the molded product by subtracting the load of the estimated sliding resistance (F2 ′) from the mold release load profile (F1). Mold release force detection method. The estimated load of the ejector pin sliding resistance (F2 ′) is obtained by interpolating an approximate expression based on the point at which effective release is started and the point at which release is completed into the release load profile (F1). The mold release force detection method of the molded product according to claim 1 to be estimated. Means for detecting the load applied to the ejector pin by the operation of releasing the molded product by sliding the ejector pin in the molding die and outputting it as a load signal;
Means for collecting and analyzing the load signal to detect a release load profile (F1);
Means for estimating the load of the sliding resistance (F2 ′) of the ejector pin based on the release load profile (F1);
A molded product comprising means for obtaining an effective mold release force applied to the molded product by subtracting the estimated sliding resistance (F2 ′) load from the mold release load profile (F1). Release force detection device.

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