JPH076932B2 - Apparatus for measuring cure shrinkage force of thermosetting resin and method for measuring cure shrinkage force using the apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus for measuring the curing shrinkage force of a thermosetting resin and a method for measuring the curing shrinkage force using the apparatus. For example, the thermosetting resin used for the exterior of electronic parts is
If the shrinkage force associated with the curing is too strong, it may cause cracks in the electronic component or deteriorate the characteristics of the electronic component. Therefore, it is necessary for the thermosetting resin as the exterior resin of the electronic component to know the shrinkage force during curing in advance. This invention
It relates to an improved apparatus and method for measuring the shrinkage force during cure of such thermosetting resins.

2. Description of the Related Art Generally, a strain gauge is used to measure the shrinkage force of a thermosetting resin during curing. For example, as shown in FIG. 5, a metallic ring 3 made of, for example, iron is fixed to the center of the inner bottom surface 2 of a cylindrical container 1 having a low bottomed upper surface opening made of silicone. Attach the strain gauge 4 to the inner surface of this ring 3,
It is connected to a predetermined electronic circuit (not shown) or the like. Then, at room temperature, a thermosetting resin is injected into a space defined between the outer peripheral surface of the ring 3 and the container 1, and the thermosetting resin is placed in an electric oven device or the like and heated to cure the injected resin. At this time, the resin shrinks as it hardens, and stress is applied to the outer peripheral surface of the ring 3. Therefore, when viewed microscopically, the ring 3 is tightened from the surroundings to be contracted or distorted, and the stress at that time appears as a change in the resistance value of the strain gauge 4 attached to the inner peripheral surface of the ring 3. Therefore, the stress applied to the ring 3, that is, the shrinkage force when the thermosetting resin is cured, can be measured from the change in the resistance value of the strain gauge 4.

By the way, the strain gauge 4 generally has a strain characteristic that changes with temperature. That is, as shown in FIG. 6, the strain that can be obtained based on the change in the resistance value of the strain gauge 4, that is, the apparent strain, is greatly affected by the temperature. Further, as shown by hatching in FIG. 6, the amount of change in apparent strain due to temperature change varies within a certain range depending on the product, and the change is also non-linear.

Therefore, when actually measuring the curing shrinkage force of the thermosetting resin based on the output of the strain gauge 4,
It is necessary to obtain the true strain, not the apparent strain, and to measure the cure shrinkage force based on the true strain. For this reason, in the conventional device, two strain gauges 4 having apparent strain characteristics whose apparent strain characteristics are almost equal to each other are prepared in advance, and one strain gauge 4 is a device for measurement in which thermosetting resin is actually injected. No. 3 was attached to the ring 3, and the other was attached to the ring 3 of the dummy device in which the thermosetting resin was not injected, both were placed in the electric oven device at the same time, and the true strain was obtained by the output obtained from both. . That is,
The output of the strain gauge 4 attached to the measuring device is f
₁ (t), the output of the strain gauge 4 attached to the dummy device is f ₂ (t), f (t) = t ₁ (t) −f ₂ (t) where t is the true strain value due to temperature change. Was seeking.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a measuring device and measuring method, heat generated by the thermosetting resin during curing is not taken into consideration, and the curing shrinkage force of the thermosetting resin accompanied by heat during curing is not considered. It has the drawback that it cannot be used for measurements. This is because even if the measuring device and the dummy device are put in the same electric oven device and heated, only the heat generated by the curing of the thermosetting resin is equivalent to the strain gauge 4 of the measuring device.
This is because the temperature becomes higher and the apparent strain obtained by the strain gauge 4 of the dummy device cannot be said to be the characteristic obtained under the same conditions as those of the measuring device. Therefore, many thermosetting resins used for the exterior of electronic parts, especially thermosetting resins used for ceramic electronic parts, generate heat as they cure, and the conventional device as described above and the measuring method using the device. There was a problem that was not available.

Further, even if the thermosetting resin does not generate heat during curing, the strain gauge 4 has variations in the apparent strain characteristics for each product as described above. Therefore, even if gages with similar apparent strain characteristics are used for the measuring device and the dummy device, respectively, there is some difference in the characteristics between the two, and the difference cannot be ignored in conventional devices. ,
There is also a problem that the conventional device cannot be used when the measurement result is strongly required to be strict.

Means for Solving the Problems Then, the device of the present invention is configured as follows.

A container having an inner bottom surface and an inner side surface, and a cylindrical body that is arranged upright in a substantially central portion of the inner bottom surface of the container so that the central axis is in a vertical direction, and the outer peripheral surface of the cylindrical body and the inner bottom surface of the container are included. The thermosetting resin to be measured is placed in the space defined by the inner surface and the inner surface, and the contraction force when the thermosetting resin cures is applied to the outer peripheral surface of the inner peripheral surface of the cylinder. At this time, a strain gauge whose resistance value changes according to the pressure is attached, and a hole is formed in the upper end surface of the side wall of the cylindrical body, and the temperature detecting unit of the temperature detecting means is inserted in the hole. There is. The temperature detecting means is adapted to measure the temperature of the cylindrical body which can be regarded as the temperature of the strain gauge in order to correct the amount of strain accompanying the temperature change of the strain gauge. Then, the apparent strain detecting means is electrically connected to the strain gauge, and the apparent strain applied to the outer peripheral surface of the cylindrical body is detected based on the resistance change generated in the strain gauge. Further, the temperature detecting means and the apparent strain detecting means are coupled with the correction calculating means, whereby the apparent strain detected by the apparent strain detecting means is based on the change amount caused by the temperature change in the resistance change occurring in the strain gauge. To correct.

In the preferred embodiment, the temperature sensing means comprises a thermocouple and the temperature sensing portion is placed in the hole described above and the gap is sealed with silicone. Further, as the container, for example, a container whose inner surface is formed of silicone and has a good releasability and whose circumference is circular is used.

Another method invention according to this application is constituted by the following steps shown in to.

That is, the measuring device described above is prepared. The prepared device is placed in an atmosphere in which the temperature can be changed, with the resin to be measured empty. For example, place the device in an electric oven device. The temperature of the atmosphere in which the device is placed is raised from room temperature to the temperature required for curing the resin to be measured, plus the exothermic temperature generated when the resin is cured. The resistance value of the strain gauge that changes as the temperature of the atmosphere rises and the temperature detected by the temperature detection means at that time are read out at a plurality of points to obtain the temperature-resistance value relationship. At this time, the more points to read, that is, the more detection points how the resistance value of the strain gauge changes due to temperature change, the better. Next, based on the obtained temperature-resistance value relationship, a temperature-apparent strain function F (t) representing a change in apparent strain due to a temperature change in the strain gauge is calculated. If this calculation is preferably performed by a microcomputer, it can be obtained in a short time. Next, the resin to be measured is put into the prepared apparatus and placed in an atmosphere in which the temperature can be changed. And
The temperature of the atmosphere is raised from room temperature to the temperature required for curing the resin to be measured. At this time, the resistance value of the strain gauge that changes as the temperature of the atmosphere rises and the temperature detected by the temperature detecting means at that time are detected. Calculate the apparent strain based on the resistance value detected in <>.
The apparent strain under a specific temperature is obtained by the temperature-apparent strain function calculated in <> and the temperature obtained by the temperature detecting means in <>. Then, the apparent strain found in <> is subtracted from the apparent strain found in <> to find the true strain.

Action In the device of the present invention and the method for measuring the curing shrinkage force of a thermosetting resin using the device, the device is preheated in an empty state, and the apparent strain function based on the temperature change of the strain gauge is obtained. Next, the thermosetting resin to be measured is actually put and heated to cure the resin, and the strain change of the strain gauge at that time is obtained. Then, at that time, the apparent strain corresponding to the temperature is corrected by the above function. The temperature of the strain gauge is almost the same as the temperature of the atmosphere when the equipment is empty, but when the resin to be measured is put in the equipment, the temperature of the atmosphere and the temperature of the strain gauge are generated by the heat generated when the resin cures. And do not match. Therefore,
In this invention, the exact temperature in each state of the strain gauge is
It is detected by the temperature detecting means. Therefore, the apparent distortion function and the correction using the function are accurately performed.

Embodiment FIG. 1 is a schematic view of an apparatus 20 of a preferred embodiment of the present invention and the apparatus connected to a microcomputer 15. FIG. 2 is an enlarged partial view of the device 20 of FIG.

Referring to FIGS. 1 and 2, the container 1 has a low cylindrical shape and has a bottom 2. The container 1 is made of silicone so as to have a good releasability. At the center of the inner bottom surface 2 of the container 1, a concentric cylindrical ring 3 made of, for example, iron is arranged. The ring 3 is fixed to the inner bottom surface 2 of the container with, for example, an adhesive. A strain gauge 4 is attached to the inner peripheral surface of the ring 3. The strain gauge 4 is arranged near the center of the ring 3 in the height direction and along the circumferential direction of the ring 3, and is attached to the inner surface of the ring 3 with a phenolic thermosetting adhesive so as to be in close contact with the ring 3. Has been. Therefore, the slight expansion and contraction of the ring 3 is directly transmitted to the strain gauge 4.

As shown in FIG. 2, the strain gauge 4 has a plurality of resistance wires 42 made of, for example, nickel-copper alloy arranged in parallel in a predetermined direction on, for example, a polyimide thin film piece 41 or a bakelite paper piece 41. It was placed in. The strain gauge 4 is such that the member to which it is attached expands and contracts in a microscopic manner, whereby the length of the resistance wire changes and the resistance value changes. Generally, this change in resistance value is measured as a change in voltage, and the strain of the adhered member or the force applied to the member is obtained.

With further reference to FIG. 2, the ring 3 has a hole 8 formed downward from the upper end surface 7 of the side wall.
A thermocouple 9 is inserted in. The gap between the upper end of the hole 8 and the thermocouple 9 is sealed with silicone 10. The thermocouple 9 measures the temperature of the ring 3, in other words, the temperature of the ring 3, which can be regarded as the temperature of the strain gauge 4 attached to the ring 3.

Here, the measurement principle of the resistance change of the strain gauge 4 used in this embodiment and the connection method in that case will be described with reference to FIGS. 3A to 3C.

Generally, a bridge circuit as shown in FIG. 3A is used to measure the resistance change. For the bridge circuit of FIG. 3A, the following equation holds.

e = (1/4) {ΔR1 / R1−ΔR2 / R2 + ΔR3 / R3−ΔR4 / RS} E where ΔR / R: rate of change of resistance Therefore, if strain gauge 4 is connected instead of resistance R1,
A change in the resistance of the strain gauge can be detected by a change in the output voltage e. However, when connecting the strain gauge 4 to this bridge circuit, if the connecting lead wire from the strain gauge 4 to the bridge circuit is long, the resistance value of the lead wire is added in series to the resistance value of the strain gauge 4, In addition, the resistance of the lead wire changes slightly depending on the temperature and must be removed. Therefore, as shown in FIG. 3B, a so-called three-wire connection system is adopted in this embodiment. This three-wire connection method is equivalently a bridge circuit as shown in FIG. 3C, and the reciprocating lead wires 43 and 44 to which the strain gauge 4 is connected respectively enter into different pieces of the bridge circuit on one side respectively, and both are the same. Due to the resistance value r and the temperature coefficient of resistance, the change is canceled. In addition, lead-in lead 45
The resistance value r of does not affect the circuit for voltage measurement.

Returning to FIG. 1, the output of the strain gauge 4 and the thermocouple 9
The output of is given to a predetermined circuit composed of the microcomputer 15, for example. That is, strain gauge 4
Is output to the apparent strain detection circuit 11, and the thermocouple 9
Is supplied to the temperature-apparent distortion correction circuit 12.
The apparent strain detection circuit 11 detects the apparent strain from the resistance change rate measured based on the above-described principle, and outputs it to the temperature-apparent strain correction circuit 12. The temperature-apparent strain correction circuit 12 includes a memory 16 in which an apparent strain function F (t) obtained in advance is stored, and based on the temperature given from the thermocouple 9 and the apparent strain function F (t). The apparent strain calculated from the resistance change of the strain gauge 4 is corrected, and the corrected value is displayed on the display device 13 and printed by the printing device 14.

Next, a measuring method in the case of measuring the curing shrinkage force of the thermosetting resin using this embodiment described above will be described.
In the following description, the apparatus 20 of this embodiment is connected to the microcomputer 15 as described above, and the microcomputer 15 heat-sets the strain value of the strain gauge 4, in other words, the ring 3 to which the strain gauge 4 is attached. A method of calculating the shrinkage force of the resin will be described.

FIG. 4A and FIG. 4B are flow charts for explaining the operation of the microcomputer 15, and the measurement of the curing shrinkage force of the thermosetting resin using this example is performed in the order according to this flow chart. Of FIGS. 4A and 4B, FIG. 4A is a flow chart in the case where the apparatus 20 is heated in an empty state and the apparent strain function F (t) of the strain gauge 4 is obtained in advance. The figure is a flow chart in the case where a thermosetting resin to be measured is put into this device 20 and the curing shrinkage force thereof is measured.

First, a description will be given with reference to FIG. 4A. As shown in FIG. 1, this device 20 is prepared and connected to the microcomputer 15 so that the output of the strain gauge 4 and the output of the thermocouple 9 are given to the microcomputer 15. Then, this device 20 is put in, for example, an electric oven device (not shown), and is gradually heated from room temperature to a high temperature by the oven device. The microcomputer 15 reads the temperature which is the input of the thermocouple 9, for example, the resistance value of the strain gauge 4 is read every time the temperature rises by 10 ° C., and the apparent strain is detected. Then, the temperature is determined by adding the exothermic temperature when the resin is cured to the temperature required for curing the resin to be measured in advance, for example, until the temperature rises to 300 ° C, reading of the above temperature in 10 ° C increments and apparent strain Repeat detection of. Then, when the measurement is completed, the microcomputer calculates an apparent strain function F (t) due to temperature based on the reading and detection results. Then, the function F (t) is stored in the memory 16,
Finish the operation.

Next, the thermosetting resin to be measured is put into the apparatus 20 of this embodiment. The thermosetting resin is applied to the ring 3 as described above.
It is placed in a space surrounded by the outer peripheral surface of the container 1, the inner bottom surface 2 of the container 1, and the inner peripheral surface. Then, it is placed in, for example, an electric oven device and gradually heated from room temperature to a predetermined curing temperature by the electric oven device. At this time, the microcomputer 15 connected to the device 20 of this embodiment reads the resistance change detected by the strain gauge 4 every time the temperature, which is the output of the thermocouple 9, rises by, for example, 10 ° C. The microcomputer 15 calculates the apparent strain St based on the read resistance change.

Next, the calculated strain St is corrected based on the function F (t) stored in the memory 16. That is, for example, if the apparent strain calculated at the temperature t ₁ is St ₁ ,
From the calculated strain St ₁ to the function F (t at the temperature t ₁
Subtract ₁ ) to correct the apparent strain due to the temperature change of strain gauge 4.

In this way, for example, the measurement is repeated every time the temperature rises by 10 ° C., and the measurement is performed until the thermosetting resin cures and returns to room temperature. Then, the obtained measurement value is displayed on the display device 13 or printed by the printing device 14, and the measurement operation is completed.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to provide a device that can accurately measure the curing shrinkage force of a thermosetting resin, and a measuring method using the device. Particularly, even if the thermosetting resin generates heat during curing, the apparent strain of the strain gauge caused by the heat is corrected, and an actual curing shrinkage force can be accurately measured, and a measuring method using the device is provided. You can

[Brief description of drawings]

FIG. 1 is a perspective view showing an apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged partial view of the device of FIG. 3A
3 to 3C are circuit diagrams showing the principle of measuring the rate of change in resistance by the strain gauge 4 and the wiring method thereof. Figures 4A and 4B
The figure is a flow chart showing the operation sequence when this device is connected to a microcomputer for measurement. FIG. 5 is a perspective view showing a conventional apparatus for measuring the curing shrinkage force of a thermosetting resin. FIG. 6 is a strain-temperature characteristic diagram of the strain gauge. In the figure, 1 is a container, 2 is the inner bottom surface of the container, 3 is a cylindrical ring, 4 is a strain gauge, 8 is a hole formed in the ring,
9 indicates a thermocouple.

Claims (7)

[Claims] 1. A device for measuring a shrinkage force generated by hardening a thermosetting resin when the thermosetting resin is put in the container, the container having an inner bottom surface and an inner side surface, and The inner bottom surface includes substantially a central portion, and a cylindrical body that is arranged upright so that the central axis is in a vertical direction. The resin is provided in a space defined by the outer circumferential surface of the cylindrical body and the inner bottom surface and the inner side surface of the container. Is attached to the outer peripheral surface of the cylindrical body, and when the contracting force when the resin cures is applied to the outer peripheral surface of the cylindrical body, the resistance value changes according to the contracting force. Strain gauge to be, and a hole is formed in the upper end surface of the side wall of the cylindrical body, the temperature detecting portion is inserted in the hole, in order to correct the strain amount due to the temperature change of the strain gauge, of the strain gauge. The above, which can be regarded as temperature Temperature detection means for measuring the temperature of the cylindrical body, electrically connected to the strain gauge, the apparent strain detection means for detecting the apparent strain applied to the cylindrical outer peripheral surface based on the resistance change occurring in the strain gauge, A correction calculation unit that is coupled to the temperature detection unit and the apparent strain detection unit, and based on a change amount caused by a temperature change among resistance changes generated in the strain gauge, corrects the apparent strain detected by the apparent strain detection unit. An apparatus for measuring the curing shrinkage force of a thermosetting resin, including: 2. The apparatus for measuring the curing shrinkage force of a thermosetting resin according to claim 1, wherein the temperature detecting means is a thermocouple. 3. The thermosetting resin curing shrinkage force measuring device according to claim 2, wherein the thermocouple has a temperature detecting portion inserted in the hole and a gap is sealed with silicone. 4. The apparatus for measuring the curing shrinkage force of a thermosetting resin according to claim 1, 2, or 3, wherein the container is a container having a good releasability. 5. The container is made of silicone,
A fourth aspect of the present invention, wherein the inner surface has a circumferential shape.
An apparatus for measuring the curing shrinkage force of a thermosetting resin according to the item. 6. The thermosetting method according to claim 1, wherein the strain gauge is bonded with a thermosetting adhesive along the circumferential direction of the cylindrical body. Measuring device for curing shrinkage force of resin. 7. An apparatus for measuring a shrinkage force generated by hardening a thermosetting resin when the thermosetting resin is placed in the container, the container having an inner bottom surface and an inner side surface; The inner bottom surface includes a cylindrical body which is vertically arranged with its central axis in a substantially central portion, and the resin is provided in a space defined by the outer peripheral surface of the cylindrical body and the inner bottom surface and the inner side surface of the container. Is attached to the outer peripheral surface of the cylindrical body, and when the contracting force when the resin cures is applied to the outer peripheral surface of the cylindrical body, the resistance value changes according to the contracting force. Strain gauge to be, and a hole is formed in the upper end surface of the side wall of the cylindrical body, the temperature sensing portion is inserted into the hole, in order to correct the strain amount due to the temperature change of the strain gauge, The cylinder that can be regarded as temperature A first step of preparing a device including a temperature detecting means for measuring the temperature of the device; and And a third step of increasing the temperature of the atmosphere in the second step from room temperature to a temperature required for curing the resin to be measured plus a heat generation temperature when the resin is cured, In the third step, the resistance value of the strain gauge that changes with the temperature rise of the atmosphere and the temperature output by the temperature detection means at that time are detected, and the resistance value of the strain gauge at a plurality of temperatures-the temperature Based on the fourth step of obtaining the relationship and the resistance value-temperature relationship obtained in the fourth step, a temperature-apparent strain function representing the change of the apparent strain due to the temperature change of the strain gauge is previously set. A fifth step of calculating, a sixth step of placing a resin to be measured in the apparatus and arranging the apparatus in an atmosphere in which the temperature can be changed, and a temperature of the atmosphere in the sixth step is room temperature To a temperature required for curing the resin to be measured, and a resistance value of the strain gauge that changes with the temperature rise of the atmosphere in the seventh step, and at that time by the temperature detecting means. An eighth step of detecting the obtained temperature, a ninth step of obtaining an apparent strain based on the resistance value detected in the eighth step, and the temperature calculated in advance in the fifth step A tenth step of obtaining an apparent strain under a specific temperature by an apparent strain function and a temperature obtained by the temperature detecting means in the eighth step, and from the apparent strain obtained in the ninth step. An eleventh step of subtracting the apparent strain obtained in the tenth step to obtain a true strain, and a method for measuring the curing shrinkage force of a thermosetting resin using a device for measuring the curing shrinkage force.