JPS582375B2 - Handanure Seishiken Sochi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring the solderability of electronic components, printed circuit boards, etc.

Among conventional wettability testing methods, there is an interfacial tension wetting test method that quantitatively displays wettability, has good measurement accuracy, and is relatively easy to handle.

This method uses a strain gauge or the like to detect the interfacial tension between the test piece and the molten solder, which occurs when the test piece is immersed in the molten solder.

However, in conventional devices, the initial strain applied to the strain gauge varies each time the weight of the sample changes.

Figure 2 is a diagram showing the relationship between the strain of the strain gauge and the change in characteristic values.
When using a strain gauge whose strain-resistance value characteristics are in the relationship shown by curve 16, the strain gauge has ε.

When sample 4 is attached, which has a weight that causes a strain such as ε.

When a sample 4' having a weight that causes a strain of ε0+ε1 is attached to the strain gauge, ε.

This results in a distortion of +ε1.

If these two samples 4 and 4' both have wettability that causes a strain of ε1, a strain of ε0 + ε1 will occur for sample 4, a strain of ε0 + 2ε1 will occur for sample 4', and as an output, sample 4 will have a resistance value. R0+R1, and sample 4' has a resistance value of R0+R1.
+R2.

In this way, even if the wettability is the same, the output is different, so a direct comparison cannot be made and it is necessary to always perform conversion.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to automatically adjust the initial strain amount of the strain gauge due to the difference in sample weight to a constant value, thereby improving the accuracy of measuring the degree of wetness. The purpose of the present invention is to provide a solderability testing device that increases the efficiency of work.

In order to achieve the above objective, a movable balance weight is installed in a part of the arm of the solderability testing device, so that the amount of strain acting on the strain gauge is always constant in the initial state according to changes in the weight of the test piece. It has a mechanism that automatically moves the balance weight.

The present invention will be explained below with reference to Examples.

An embodiment of the invention is shown in FIG.

In this figure, the solder bath 3 is installed on the lifting platform 2,
It can be moved up and down freely using a separate drive device (not shown in this figure).

The arm 6 has a sample holder 5 at one end, and a balance weight 11 and a balance weight moving device 13 according to the invention are attached to the other end.

One end of the strain gauge 8 is attached to a strain gauge mounting bracket 7 provided on the arm 6, and the other end is fixed to a support 10 erected from the pedestal 1.

Further, the arm 6 is supported by a fulcrum 9 and a fulcrum stand 12.

The output from the strain gauge 8 is transmitted to a strain detection device 1 that converts the amount of strain into voltage by incorporating the strain gauge into a resistor bridge, for example.
4 and detected by the distortion detection device 14, for example, is amplified by the amplifier 15, and the motor is equipped with a DC motor whose rotational speed and direction are determined by the magnitude and polarity of the voltage, for example. Balance weight moving device 13
sent to.

The balance weight moving device 13 is set to move the balance weight in the axial direction of the arm 6 in response to a signal sent from the amplifier 15, and to stop when the signal input becomes zero.

For such a device, first attach the sample 4 to the sample mounting bracket 5, and then turn on the power (not shown in the figure) connected to the strain detection device 14, amplification device 15, and balance weight moving device. A tension is applied to the gauge, and a signal having a magnitude proportional to this tension is detected by the strain detection device 14.

This signal is amplified by the amplifier 15 and sent to the balance weight moving device 13.

In this case, the strain gauge 8 has a structure that always detects only the tension, so if the tension becomes zero, the support of the arm 6 may become unstable. A circuit is configured so that the output signal from the strain gauge becomes zero when a constant tension is applied to the gauge.

In this state, if the tension acting on the strain gauge is below the above-mentioned certain value, a negative signal will be detected.
In this case, the balance weight moving device 13 acts to move the balance weight closer to the fulcrum 9, and as the balance weight moves, the tension of the strain gauge increases, approaches the above-mentioned constant strain value, and matches the constant value. At this point, the strain detected by the strain detection device 14 becomes zero, and the movement of the balance weight 11 stops.

When the tension is equal to or greater than the above-mentioned constant strain value, a positive signal is generated, and the balance weight 11 moves in a direction away from the fulcrum 9, and stops when the signal becomes zero.

In this way, balance weight 1 is placed at a position where the tension on the strain gauge is always constant regardless of the weight of sample 4.
1, the output from the strain gauge 8 is switched to a measuring device such as a recorder, and the wettability test is started.

As explained above, according to the present invention, when the sample 4 is attached to the sample fixture 5, regardless of the weight of the sample 4,
The tension acting on the strain gauge 8 is always set to a constant value.

Therefore, the troublesome operation of removing the influence of the sample weight from the measured value every time the sample weight differs, as in the conventional method, becomes unnecessary, and work efficiency can be improved.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the solder wetting test device according to the present invention, and FIG. 2 shows the relationship between the amount of strain of the strain gauge and the change in characteristic value R. 3...Solder bath, 4,4'...Sample, 6...Arm, 8
...Strain gauge, 11...Balance weight, 13...Balance weight moving device,

Claims (1)

[Claims] 1 Support one point of the arm with a support fixed on the pedestal,
A sample 2 fixture is provided at one end of the arm via this fulcrum, and an arm portion having a balance weight and a balance weight moving device at the other end, and a strain gauge fixture is provided on a part of the arm, and this mounting bracket and a strain detection section with a strain gauge attached parallel to the arm section between the pillar fixed on the pedestal, and the balance weight of the arm section is moved by the output of the strain detection section to determine the measurement starting point. A solderability testing device characterized by having a mechanism that automatically adjusts to a constant point at all times.