JPS6175247A - Cure shrinking force measuring apparatus for thermosetting resin and cure shrinking force measurement using the same - Google Patents

Abstract

PURPOSE:To achieve a temperature correction for the measured value, by measuring a shrinking force working on a cylinder with the curing of a resin with a strain gauge attached on the inner surface of the cylinder errected in a container while the temperature is done with a temperature checking section at the upper end of the side wall of the cylinder. CONSTITUTION:A measuring apparatus 20 is heated empty with an electric oven gradually up to a high temperature from the room temperture while the temperature thereof is read from the input of a thermocouple 9 with a microcomputer 15. For example, the resistance of a strain gauge 4 is read at an interval of 10 deg. to detect an apparent strain. This operation is repeated until the addition of the temperature required for the hardening of a resin to be measured and the temperature of heat generated by hardening reaches, for example, 300 deg.C. Moreover, an apparent strain function due to temperature is determined with a microcomputer 15 to be memorized into a memory 16. Then, a thermosetting resin to be measured is placed into a space surrounded by the outer surface of a ring 3 and the inner bottom surface 2 of a container 1 and the inner surface and the same operation is done to calculate an apparent strain, which is corrected by an apparent strain function and then, the results are shown on a display 13 as measured value.

Description

[Detailed Description of the Invention] Industrial Application This invention is for measuring the curing shrinkage force of thermosetting resin! This invention relates to a curing shrinkage force measuring method using the apparatus. For example, thermosetting resins used for the exterior of electronic components, etc.
If the shrinkage force accompanying 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 to know in advance the shrinkage force of the thermosetting resin used as the exterior resin for electronic components when it is cured. This invention is
The present invention relates to an improved apparatus and method for measuring the shrinkage force of such thermosetting resins during curing.

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 ring 3 made of metal, such as iron, is fixed to the center of the inner bottom surface 2 of a cylindrical container 1 made of silicone and having a bottom and a low upper opening. A strain gauge 4 is attached to the inner peripheral surface of this ring 3,
Connect to a predetermined electronic circuit (V in the figure), etc. Then, under air temperature, a thermosetting resin is injected into the space defined between the outer peripheral surface of the ring 3 and the container 1, and the injected resin is cured by placing it in an electric oven or the like and heating it. .

At this time, the resin contracts as it hardens, and stress is applied to the outer peripheral surface of the ring 3. Therefore, from a microscopic perspective, the ring 3 is compressed or distorted by being tightened from its surroundings, 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 from this change in resistance value of the strain gauge 4,
In other words, the shrinkage force of the thermosetting resin during curing can be measured.

By the way, the strain characteristics of the strain gauge 4 generally change depending on the temperature. In other words, as shown in Fig. 6, the strain that can be determined based on the change in resistance (approximately 1) of the strain gauge 4, that is, the apparent strain, is greatly affected by temperature. As shown, 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 contraction force of the thermosetting resin based on the output of the strain gauge 4, it is necessary to use the strain gauge 4.
It is necessary to determine the true strain, not the apparent strain, and measure the curing shrinkage force based on it. For this purpose, in conventional equipment, two strain gauges 4 having approximately the same apparent strain characteristics are prepared, and one strain gauge 4 is used as a measuring device for actually injecting the thermosetting resin. The other is attached to the ring 3 of the dummy device without injecting thermosetting resin, and both are placed in the electric oven device at the same time, and the true strain is determined by the output obtained from both.

was looking for. In other words, if the output of the strain gauge 4 attached to the measuring device is r+(t>, and the output of the strain gauge 4 attached to the dummy device is r2 (t), then f (t) - fl (t) - f 2 ( t) However, for t, the true strain value was determined by temperature change.

Group 1. However, such measurement devices and measurement methods do not take into account the heat generated by thermosetting resins when they cure. The disadvantage was that it could not be used.

This is because even if the measuring device and the dummy device are placed in the same electric oven and heated, the strain gauge 4 of the measuring device will have a higher temperature due to the heat generated as the thermosetting resin hardens. This is because 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 that of the measuring device. Therefore, thermosetting resins used for the exterior of electronic components,
In particular, many of the thermosetting resins used in ceramic electronic components generate heat upon curing, and the conventional apparatus and measurement method using the apparatus as described above cannot be used.

Furthermore, even if the thermosetting resin does not generate heat during curing, the strain gauge 4 has variations in apparent strain characteristics depending on the product, as described above.

Therefore, even if gauges with similar apparent strain characteristics are used for the measuring device and for the dummy device, there will be some differences in the characteristics between the two, and these differences must be tolerated with conventional devices. However, there is also the problem that conventional devices cannot be used when strict accuracy is required for the measurement results.

In order to solve the problem, the apparatus of the present invention is constructed as follows.

A container having an inner bottom surface and an inner surface, and a cylindrical body disposed vertically in the center of the inner bottom surface of the container, the outer circumferential surface of the cylindrical body and the inner bottom surface of the container. The thermosetting resin to be measured is placed in the space defined by the inner surface and the inside surface, and the shrinkage force when the thermosetting resin hardens is applied to the outer circumferential surface of the cylindrical body. 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 a temperature measuring part of the temperature detection means is inserted into the hole. There is. The humidity sensing means measures the temperature of the cylindrical body, which can be regarded as the temperature of the strain gauge, in order to correct the strain bow caused by temperature changes in the strain gauge.

In a preferred embodiment, the temperature sensing means comprises a thermocouple, the temperature measuring part being placed in the hole described above and the gap sealed with silicone. Further, the container is made of silicone and has a circumferential inner surface with good mold releasability.

Another method invention according to this application is constituted by the following steps (1) to (4).

That is, (1) Prepare the above-mentioned 5A measurement device. ■Place the prepared device in an empty state with no resin to be measured in an atmosphere where the temperature can be varied. For example, electric oven If? Place the device in the il. (2) Raise the temperature of the atmosphere in which the device is placed from room temperature to the temperature required to cure the resin to be measured plus the exothermic temperature generated when the resin cures. (2) The resistance value of the strain gauge, which changes as the temperature of the atmosphere rises, and the humidity detected by the temperature detection means at that time are read out at a plurality of points, and the relationship between temperature and resistance value is determined. At this time, the more points to read out, ie, the points to detect how the resistance value of the strain gauge changes due to temperature changes, the better. ■Next,・
Based on the obtained temperature-resistance value relationship, a resistance value change characteristic function (apparent strain function) F (t ) due to temperature change of the strain gauge is calculated. If this calculation is preferably performed by a microcomputer, it can be obtained in a short time. (2) Next, the resin to be measured is placed in the prepared device and placed in an atmosphere where the temperature can be varied.

(2) Then, the temperature of the atmosphere is raised from room temperature to the temperature necessary for curing the resin to be measured. (2) At this time, the resistance value of the strain gauge, which changes as the temperature of the atmosphere rises, and the temperature detected by the temperature detection means at that time are detected.

■By subtracting the value of the previously calculated function F ([) from the resistance value of the strain gauge at each detected temperature, the resistance value of the strain gauge at each temperature is corrected, and the corrected strain characteristics are obtained. .

l In the method of measuring the curing shrinkage force of a thermosetting resin using the apparatus of the present invention and its 5A@, the apparatus is heated in advance in an empty state, and an apparent strain function is determined based on the temperature change of the strain gauge. Next, a thermosetting resin to be measured is actually put in and heated to harden the resin, and the strain change on the strain gauge at that time is determined. At that time, the apparent strain corresponding to the temperature is corrected using the above function. The temperature of the strain gauge almost matches the ambient temperature when the device is empty, but when the resin to be measured is placed in the device, the temperature of the atmosphere and the temperature of the strain gauge will differ due to the heat generated when the resin hardens. do not match. Therefore,
In this invention, the exact temperature in each state of the strain gauge is
The temperature is detected by a temperature detection means. Therefore, the above apparent distortion function and correction using the function can be performed accurately.

31 FIG. 1 is a schematic diagram of the device 20 of the preferred embodiment of the invention and its connection to the microcomputer 15. FIG. 2 is an enlarged partial view of the apparatus 20 of FIG.

Referring to FIGS. 1 and 2, the container 1 is of low cylindrical shape and has a bottom 2. In FIG. The container 1 is made of silicone for good mold releasability. At the center of the inner bottom surface 2 of the container 1, a cylindrical ring 3 made of, for example, iron is arranged concentrically. The ring 3 is fixed to the inner bottom surface 2 of the container, for example with 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 in the height direction of the ring 3 along the circumferential direction of the ring 3, and is pasted to the inner peripheral surface of the ring 3 using, for example, a phenolic thermosetting adhesive. It is attached. Therefore, slight expansion and contraction of the ring 3 is directly transmitted to the strain gauge 4.

As shown in FIG.
For example, a resistor made of a nickel-copper alloy; A42
are arranged so that a plurality of them are lined up in parallel in a predetermined direction. In the strain gauge 4, the resistance value changes as the length of the resistance wire changes as the member to which it is attached expands and contracts microscopically. Generally, this resistance value change is measured as a voltage change, and the strain on the attached member or the force applied to the member is determined.

Further referring to FIG. 2, a hole 8 is formed in the ring 3 downward from the upper end surface 7 of the side wall.
A thermocouple 9 is inserted into. The gap between the upper end of the hole 8 and the thermocouple 9 is sealed with silicone 10.

This 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, with reference to FIGS. 3A to 3C, the principle of measuring the resistance change of the strain gauge 4 used in this embodiment and the wiring method in that case will be explained.

Generally, a bridge circuit as shown in FIG. 3A is used to measure resistance changes. The following equation holds true for the bridge circuit of FIG. 3A.

e-(1/4)(ΔR1/R1-ΔR2/R2+ΔR3
/R3-ΔR4/R4)E However, ΔR/R: Rate of change in resistance Therefore, if strain gauge 4 is connected in place of resistor R1, the change in resistance of the strain gauge can be detected by the change in output voltage e. can. 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, Moreover, since the resistance of the lead wire changes minutely depending on the temperature, this must be removed. Therefore, the 3rd B
As shown in the figure, this embodiment uses a so-called three-wire connection system. This three-wire connection system is isometrically
The bridge circuit shown in the figure is formed, and the reciprocating lead wires 43 and 44 to which the strain gauge 4 is connected enter two different halves of the bridge circuit, one on each side, and both have the same resistance value r and the same resistance temperature coefficient. The changes cancel out. Note that the resistance value r of the lead-in lead 45 does not affect the circuit because the voltage is measured.

Returning to Figure 1, the output of strain gauge 4 and thermocouple 9
The output is given to a predetermined circuit constituted by, for example, the microcomputer 15. That is, the output of the strain gauge 4 is given to an apparent strain detection circuit 11, and the output of the thermocouple 9 is given to a temperature-apparent strain correction circuit 12. The apparent strain detection circuit 11 detects apparent strain from the rate of change in resistance 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 a predetermined apparent strain function F (t > is stored), and calculates the temperature based on the temperature given from the thermocouple 9 and the apparent strain function F (t ). , the apparent strain determined 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 method for measuring the curing shrinkage force of a thermosetting resin using this embodiment described above will be explained.

In the following explanation, the device 20 of this embodiment is connected to the microcomputer 15 as described above, and the microcomputer 15 calculates the strain value of the strain gauge 4, in other words, the thermal hardening applied to the ring 3 to which the strain gauge 4 is attached. The method for calculating the shrinkage force of a plastic resin will be explained below.

4A and 4B show the microcomputer 15
1 is a flowchart for explaining the operation of this embodiment, and measurement of curing shrinkage force of a thermosetting resin using this embodiment is performed in the order according to this flowchart. Of FIGS. 4A and 4B, FIG. 4A shows heating the device 2o in an empty state.
4B is a flowchart for calculating the apparent strain function F(t) of the strain gauge 4 in advance, and FIG. It is a flow diagram.

First, explanation will be given with reference to FIG. 4A. As shown in FIG. 1, this device 20 is prepared and the microcomputer 1
5 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 connected to, for example, an electric open circuit 1iW.
1 (not shown), and gradually heated from air temperature to high temperature using the oven device. Microcomputer 1
At step 5, the temperature input to the thermocouple 9 is read, and the resistance value of the strain gauge 4 is read every time the temperature rises by 10°C, for example, to detect apparent strain.

Then, the temperature is set in advance to meet the required temperature for curing the resin to be measured.
The temperature reading and apparent strain detection described above are repeated in 10°C increments until the temperature rises to tfA degrees plus the exothermic temperature when the resin is cured, for example, 300°C. When the measurement is completed, the microcomputer calculates the apparent strain F(t) due to temperature based on the reading and detection results. Then, the function F(1) is stored in the memory 16, and the operation ends.

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

Next, the calculated deflection St is corrected based on the gap number F (t') stored in the memory 16.

That is, for example, if the apparent strain calculated at the temperature t is St+, then the function F(tl) at the temperature [I is subtracted from the calculated strain St+, and the result is calculated based on the temperature change of the strain gauge 4. Correct apparent distortion.

In this way, measurements are repeated every time the temperature increases, for example, by 10° C., until the thermosetting resin is cured and the temperature returns to air. Then, the obtained measured value is displayed on the display bag W113 or printed bag fF, for example.
J14 is printed and the measurement operation ends.

In the above explanation, the output of this device was connected to a microcomputer to perform calculations and arithmetic processing. The calculation for correcting the apparent distortion St can also be performed by manual calculation.

11911 As described above, according to the present invention, it is possible to provide an apparatus that can accurately measure the curing shrinkage force of a thermosetting resin, and a measuring method using the apparatus. In particular, to provide a device and a measuring method using the device, which can correct the apparent strain of a strain gauge caused by the heat generation even when a thermosetting resin generates heat during curing, and can accurately measure the actual curing contraction force. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an apparatus according to an embodiment of the present invention. 2 is an enlarged partial view of the apparatus of FIG. 1; FIG. Third
Figures A to 3C are circuit diagrams showing the principle of measuring the rate of change in resistance using the strain gauge 4 and its wiring method. FIGS. 4A and 4B are flowcharts showing the sequence of operations when this device is connected to a microcomputer to perform measurements. FIG. 5 is a perspective view showing a conventional apparatus for measuring curing shrinkage force of thermosetting resin. FIG. 6 is a strain-temperature characteristic diagram of the strain gauge. In the figure, 1 is a container, 2 is an 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. Patent applicant Murata Manufacturing Co., Ltd. ~ Figure 2 Figure 3B Figure 4A Figure 4B Figure 5 Figure 6 逼&('C)

Claims (8)

[Claims] (1) A device for measuring the shrinkage force generated as a thermosetting resin is placed and heated and the resin hardens, comprising: a container having an inner bottom surface and an inner surface; and an inner bottom surface of the container. a cylindrical body disposed vertically with its central axis in a vertical direction; the resin is placed in a space defined by the outer peripheral surface of the cylindrical body and an inner bottom surface and an inner surface of the container; and further, a strain that is attached to the inner peripheral surface of the cylindrical body and whose resistance value changes according to the contractile force when the resin hardens and the contractile force is applied to the outer peripheral surface of the cylindrical body. A hole is formed in the upper end surface of the side wall of the gauge and the cylindrical body, and a temperature measuring part is inserted into the hole, and the temperature of the strain gauge is adjusted to compensate for the amount of strain caused by the temperature change of the strain gauge. A device for measuring curing shrinkage force of a thermosetting resin, comprising a temperature detection means for measuring the temperature of the cylindrical body. (2) The apparatus for measuring curing shrinkage force of a thermosetting resin according to claim 1, wherein the temperature detection means is a thermocouple. (3) The device for measuring the curing shrinkage force of a thermosetting resin according to claim 2, wherein the temperature measuring part of the thermocouple is placed in the hole and a gap is sealed with silicone. (4) The apparatus for measuring curing shrinkage force of a thermosetting resin according to claim 1, 2, or 3, wherein the container is a container with good mold releasability. (5) The apparatus for measuring curing shrinkage force of a thermosetting resin according to claim 4, wherein the container is made of silicone and the inner surface has a circumferential shape. (6) The thermosetting resin according to claim 1, 2, or 5, wherein the strain gauge is bonded with a thermosetting adhesive along the circumferential direction of the cylindrical body. A device for measuring curing shrinkage force. (7) further electrically connected to the strain gauge;
pressure calculation means for producing the pressure applied to the outer peripheral surface of the cylindrical body based on a resistance change occurring in the strain gauge; coupled to the temperature detection means and the pressure calculation means;
Claims 1, 2, or 6 further include a correction calculation means for correcting the output of the pressure calculation means by correcting the amount of change in resistance caused by the temperature change among the resistance changes occurring in the strain gauge. An apparatus for measuring curing shrinkage force of a thermosetting resin as described in 1. (8) A device for measuring the shrinkage force generated as a thermosetting resin is placed and heated and the resin hardens, the container having an inner bottom surface and an inner surface, and an inner bottom surface of the container. a cylindrical body disposed in an upright manner with its central axis in a vertical direction substantially in the center, and the resin is placed in a space defined by the outer peripheral surface of the cylindrical body and an inner bottom surface and an inner surface of the container. and further, a strain that is attached to the inner peripheral surface of the cylinder, and whose resistance value changes according to the contractile force when the resin hardens and the contractile force is applied to the outer peripheral surface of the cylinder. A hole is formed in the upper end surface of the side wall of the gauge and the cylindrical body, and a temperature measuring part is inserted into the hole to adjust the temperature of the strain gauge and correct the amount of strain due to temperature change of the strain gauge. preparing a device including a temperature detection means for measuring the temperature of the cylindrical body, which can be regarded as a cylindrical body, and placing the device in an atmosphere where the temperature can be varied in an empty state with no resin to be measured; The temperature of the atmosphere is raised from room temperature to the temperature required for curing the resin to be measured plus the heat generation temperature when the resin is cured, and the resistance of the strain gauge changes as the temperature of the atmosphere rises. value and the temperature output by the temperature sensing means at that time to determine the resistance value-temperature relationship of the strain gauge at a plurality of temperatures, and based on the determined resistance value-temperature relationship, A resistance value change characteristic function due to temperature change of the strain gauge is calculated in advance, a resin to be measured is placed in the device, the device is placed in an atmosphere where the temperature can be varied, and the humidity of the atmosphere is changed from room temperature to the temperature to be measured. Raising the temperature to a temperature necessary for curing the resin, detecting the resistance value of the strain gauge that changes as the temperature of the atmosphere increases and the temperature obtained by the temperature detection means at that time, and calculating the temperature in advance. A curing shrinkage force measuring device is used, which corrects the amount of change due to temperature from the detected resistance value based on the resistance value change characteristic function that has been set and the temperature obtained by the temperature detection means. Method for measuring curing shrinkage force of thermosetting resin.