JPH0690164B2 - Soldering inspection device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering inspection device for determining the quality of a soldered state of a component soldered on a circuit board.

2. Description of the Related Art Conventionally, most of the techniques in this field are visually inspected by human eyes, and almost no automation is performed.

As can be seen in some of the documents described later, the soldering part is heated by laser irradiation, and the quality of the soldering state is determined by observing the temperature change at a certain point in the heated soldering part. There is a device to do. (Sensor Technology, August 1985, Vol.2, No. 9, p. 47) The soldering part here is the part's terminals and circuits that are involved in the soldering of parts' terminals. This is a general term for patterns and solders, and will be used in the same meaning below.

Problems to be Solved by the Invention Problems in the conventional technology are listed below.

(1) Problems in Visual Inspection Recently, electronic components are tending to be miniaturized and are mounted on a printed circuit board at high density. Therefore, it is difficult to visually detect defects such as poor soldering conditions where the solder joint between the component terminals and the circuit pattern is only a part, and cavities inside the solder that cannot be seen from the outside. is there. In addition, since a person makes a pass / fail judgment, there are variations due to the degree of skill and fatigue, and it is difficult to make a stable and accurate pass / fail determination.

(2) Problems of the example described in the literature In the device of the literature example, the infrared temperature detector detects the temperature change at a certain point in the heating part when the soldering part is heated by one laser. The quality of the soldering state is determined based on the difference between the temperature change in the normal soldering state and the temperature change in the defective soldering state.

Generally, the temperature change of the heating part is greatly affected by the heat capacity of the soldering part. However, during normal soldering, the solder rises above the terminals or melts and flows into the gap between the circuit pattern and the terminals.
The way the solder goes up onto the terminal and the way it flows into the gap are not always uniform, and the amount of solder on the circuit pattern varies with the amount of solder attached to the terminal. Therefore, there are variations in the heat capacity of the solder on the circuit pattern and the heat capacity of the terminal, and it is difficult to make a good / bad judgment with high accuracy by detecting only the heat capacity of the solder or detecting only the heat capacity of the terminal. The sensitivity of pass / fail judgment in the example device is slightly dull, and a defective soldered part may be mistakenly judged to be normal, or conversely, a normal soldered part may be judged to be defective. There was a problem in that the quality of the attached state was judged. In view of the above-mentioned drawbacks, the present invention provides a soldering inspection device that improves the sensitivity of quality determination and accurately determines quality of a soldering state.

Means for Solving the Problems In order to solve the above problems, at least the temperature of a heated portion when a terminal of a component is heated, and a solder or a circuit pattern soldered to the terminal is provided. Measure the temperature of the heated part when either one is heated, and compare the sum of the temperature of the above terminal and the temperature of the above solder or circuit pattern with the previously obtained sum of the above temperatures under normal soldering conditions. By doing so, the quality of the soldered state of the terminal is determined.

Action The technical points of the present invention are the following two.

First, the first point is to stabilize the measured temperature in a normal soldering state during heating. That is, even if there is variation in the amount of solder on the circuit pattern or variation in the amount of solder that has adhered to the terminals during normal soldering, the overall soldering part that combines the circuit pattern and the terminals Paying attention to the fact that the amount of solder is uniform, the temperature of the solder on the circuit pattern and the temperature of the terminal 5 showing a more stable value than the temperature of only the solder on the circuit pattern during heating and the temperature of only the terminals. The point is to evaluate the quality of the soldered state based on the sum of the temperatures. The first point of view prevents the normal soldering state from being erroneously determined to be defective.

The second point is to make the measured temperature in a poor soldering state at the time of heating take a value that is clearly different from the normal temperature. That is, in the case of a defective soldering state, the temperature of the solder on the circuit pattern is higher than that in the normal case, and the temperature of the terminal in the defective soldering state is
Since the temperature is higher than that in the normal case, the sum of the temperature of the solder and the temperature of the terminal on the circuit pattern in the case of the defect is higher than the normal temperature, and the difference between the defect and the normal becomes clear.
The second point of view prevents the defective soldering state from being mistakenly judged to be normal.

Since the present invention realizes the above two points by the above means, the quality of the soldering state can be stably and accurately determined.

Embodiment A soldering inspection apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of a soldering inspection apparatus according to an embodiment of the present invention. FIG. 1A is a partially cutaway top view of a circuit board to be inspected, where 1 is a circuit board, 2 is a circuit pattern, 3 is solder, 4 is a component, and 5 is a terminal of the component 4. FIG. 1 (b) is a schematic diagram of a soldering inspection device, 6 and 7 are infrared temperature detection devices, 8 and 9 are heating devices, 10 is a storage device, 11 is an arithmetic circuit, and 12 is a display device. .

Regarding the soldering inspection device configured as described above,
The operation will be described below with reference to FIGS. 1, 2, and 3.

In FIG. 1 (b), the heating device 8 heats the solder 3 for a fixed time. The infrared temperature detector 6 starts measuring the temperature of the solder 3 immediately before the heating by the heating device 8 is started, and continues the measurement for a while even after the heating is stopped.
Further, the terminal 5 of the heating device 9 is heated for a certain time at a time different from the time when the heating device 8 heats the solder 3. The infrared temperature detector 7 starts measuring the temperature of the terminal 5 immediately before the heating by the heating device 9 is started, and continues the measurement for a while even after the heating is stopped. The memory circuit 10 stores the measured temperature of the infrared temperature inspection device 6 and the measured temperature of the infrared temperature inspection device 7. The arithmetic circuit 11 performs the following two types of arithmetic operations. That is, the first calculation of the arithmetic circuit 11 is the measurement temperature of the infrared temperature inspection device 6 and the infrared temperature inspection device 7
This is an operation for obtaining the sum of the measured temperatures of. Second of arithmetic circuit 11
The calculation of is to determine whether the sum of the measured temperatures is within an allowable range of the sum of the measured temperatures obtained in advance in a normal soldering state, and if it is within the allowable range, the terminal 5 This is an operation in which the soldering state is determined to be normal, and when it is not within the allowable range, it is determined to be defective. The display device 12 displays the determination result made by the arithmetic circuit 11.

FIG. 2 shows two examples of normal soldering conditions. In FIG. 2A, the solder is the circuit pattern 2 and the terminal 5.
The minimum amount of solder required for normal soldering flows into the gap (2), and other solder remains on the circuit pattern 2. In FIG. 2B, the solder is the circuit pattern 2 and the terminal 5.
At the same time, it flows into the gap of a little more than the above and also adheres on the terminal 5.

FIG. 3 shows the time changes of the temperature of the solder 3 and the temperature of the terminal 5 and the sum of the temperature of the solder 3 and the temperature of the terminal 5 in the two types of examples shown in FIG. is there. In FIG. 3, the horizontal axis represents time and the vertical axis represents temperature. In the horizontal axis, a time section 15 is a time section in which the heating device 8 or 9 is heating, and a time section 16 is a heating device 8 or 9 in which heating is performed. Indicates a time segment that is stopped. Fig. 3 (a) is Fig. 2 (a).
The curve 21 shows the temperature of the solder 3, the curve 22 shows the temperature of the terminal 5, and the curve 23 shows the sum of the temperature of the solder 3 and the temperature of the terminal 5. Also, FIG. 3 (b) shows the time change of the temperature in FIG. 2 (b), the curve 24 is the temperature of the solder 3, the curve 25 is the temperature of the terminal 5, and the curve 26 is the temperature of the solder 3 and the temperature of the terminal 5. Indicates the sum of temperatures.

In the soldering state of FIG. 2 (a), the amount of solder heated by the heating device 8 is large, so the temperature does not rise easily during heating, and the temperature of the solder 3 shows a small value as shown by the curve 21. . On the contrary, since the amount of solder adhered to the terminal 5 heated by the heating device 9 is small, the temperature easily rises during heating, and the temperature of the terminal 5 shows a large value as shown by the curve 22.

In the soldering state of FIG. 2 (b), since the amount of solder heated by the heating device 8 is small, the temperature tends to rise during heating, and the temperature of the solder 3 is larger than that of the curve 21 as shown by the curve 24. Indicates. On the contrary, since the amount of solder attached to the terminal 5 heated by the heating device 9 is large,
It is difficult for the temperature to rise during heating, and the temperature of the terminal 5 is smaller than that of the curve 22 as shown by the curve 25.

As shown in FIGS. 3 (a) and 3 (b), even in a normal soldering state, there are variations in how the solder flows into the gap between the terminal 5 and the circuit pattern 2 at the time of soldering, Since the way the solder goes up is not uniform, the temperature of the solder 3 varies as shown by curves 21 and 24, and the temperature of the terminal 5 shows variation as shown by curves 22 and 25. Occurs. However, the sum of the temperature of the solder 3 and the temperature of the terminal 5 is, as shown by the curves 23 and 26, in the normal soldering state, the time interval 15 to the time interval 16
Shows a substantially constant value. As above, curve 23
The reason why the curve 26 and the curve 26 show almost equal values is that even if the amount of solder that adheres to the circuit pattern 2 or the amount of solder that adheres to the terminals 5 fluctuates, the heat capacity of the solder 3 and the terminals 5 as a whole is constant. It is possible that

Next, the temperature change in the normal soldering state and the temperature change in the defective soldering state will be compared and described.

FIG. 4 shows an example in which the soldering state of the terminal 5 is normal or defective. FIG. 4 (a) shows an example in which the soldering state of the terminal 5 is normal, and FIG. 4 (b) shows that the terminal 5 and the solder 3 are joined only in a very small part, and the soldering state is shown. Is an example of a defect.

FIG. 5 shows the temperature of the solder 3, the temperature of the terminal 5, and the time change of the temperature of the solder 3 and the temperature of the terminal 5 in the respective cases of FIGS. Is represented. In FIG. 5, the horizontal axis represents time and the vertical axis represents temperature, and the time intervals 15 and 16 have the same meanings as in FIG. FIG. 5 (a) shows the time change of the temperature in FIG. 4 (a), the curve 27 is the temperature of the solder 3, and the curve 28 is the terminal 5
Curve 29 shows the sum of the temperature of the solder 3 and the temperature of the terminal 5. Also, FIG. 5 (b) shows the time change of the temperature in FIG. 4 (b), the curve 31 is the temperature of the solder 3, the curve 32 is the temperature of the terminal 5, and the curve 33 is the temperature of the solder 3 and the temperature of the terminal 5. Indicates the sum of temperatures.

In the normal soldering state of FIG. 4 (a), the second
As described in the explanation of the figure, the curve showing the temperature of the solder 3
27 and the curve 28 indicating the temperature of the terminal 5 have variations and do not converge to a stable value, but the curve 29, which is the sum of the temperature of the solder 3 and the temperature of the terminal 5, shows a stable value without variation.

On the other hand, in the state in which only a small part of FIG. 4 (b) is soldered, the cross-sectional area of the contact surface between the terminal 5 and the solder 3 is small, and the thermal conductivity between the terminal 5 and the solder 3 is small. Low. Therefore, the heat applied to the solder 3 is difficult to be conducted to the terminals 5, and the amount of heat not conducted increases the temperature of the solder 3, so that the temperature curve 31 of the solder 3 becomes higher than the normal curve 27. Similarly, since the heat applied to the terminal 5 is difficult to be conducted to the solder 3, the temperature of the terminal 5 is higher than the normal curve 28 as shown by the curve 32. Therefore, the curve 33, which is the sum of the temperature of the solder 3 and the temperature of the terminal 5, is harder than the normal curve 29.

As described with reference to FIG. 3, the temperature of the solder 3 in the normal soldering state varies, and the curve 24 of the normal solder 3 shown in FIG. 3 (b) is shown in FIG. 5 (b). The value is almost the same as that of the curve 31 of the defective solder 3 in (1), and it is impossible to distinguish between the two.

Similarly, the temperature of the terminal 5 in the normal soldering state varies, and the curve 22 of the normal terminal 5 shown in FIG. 3 (a) shows that of the defective terminal 5 in FIG. 5 (b). It shows almost the same value as the curve 32, and it is impossible to distinguish between the two.

However, there is no variation in the sum of the temperature of the solder 3 and the temperature of the terminal 5 in the normal soldering state, and the curves 23, 24 and 29 of the sum in the normal case show almost equal values,
It is possible to distinguish between the sum curve 33 in the case of failure and the quality. Therefore, by using the sum of the temperatures of the solder 3 and the terminal 5, it is possible to stably distinguish between normal and defective.

As described above, according to the present embodiment, regarding the terminals of the components soldered to the circuit board, the temperature at the time of heating the terminals and the solder on the circuit pattern being soldered and the time different from the above heating time It is possible to accurately determine the quality of the soldered state of the terminal by using the sum of the temperatures when the terminal is heated.

Although the heating device 8 is provided so as to heat the solder 3 in the above embodiment, the circuit pattern 2 of the heating device 8 or both the solder 3 and the circuit pattern 2 may be heated.

Further, the infrared temperature inspection device 6 is provided so as to measure the temperature of the solder 3, but the infrared temperature inspection device 6 measures the temperature of the circuit pattern 2 or the temperature of both the solder 3 and the circuit pattern 2. May be provided.

Further, the memory circuit 10 is provided so as to store the measured temperature of the infrared temperature inspection device 6 and the measured temperature of the infrared temperature inspection device 7. However, the memory circuit 10 uses the measured temperature of the infrared temperature inspection device 6 or the infrared temperature inspection device. Of the measured temperatures of the device 7, only the measured temperature which is measured earlier may be stored, and the measured temperature which is measured later may be stored in the arithmetic circuit without storing it.

EFFECTS OF THE INVENTION As described above, the present invention, the temperature of the heating portion when the terminal of the component is heated, and the heating portion when at least one of the solder or the circuit pattern soldered to the terminal is heated. Measure the temperature of the
By comparing the sum of the temperatures of the solder or the circuit pattern with the sum of the temperatures obtained in advance in the normal soldering state, it is possible to accurately determine the quality of the soldering state.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a soldering inspection apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view of two types of soldering examples in which the soldering state is normal, and FIG. 3 is measured by this embodiment. FIG. 4 is a graph showing the time variation of the temperature of the terminals of the components, the time variation of the temperature of the solder, and the time variation of the sum of the two temperatures in FIG.
The figure is a sectional view in each case of a normal soldering state and a bad soldering state, and FIG. 5 is a case of each of the normal soldering state and the bad soldering state of FIG. 4 measured by this embodiment. It is a graph which shows the time change of the temperature of the terminal of a component, the time change of the temperature of solder, and the time change of the sum of the two temperatures. 1 ... Circuit board, 2 ... Circuit pattern, 3 ... Solder,
4 ... Parts, 5 ... Terminals, 6, 7 ... Infrared temperature detector, 8, 9 ... Heating device, 10 ... Memory circuit, 11 ... Arithmetic circuit, 13 ... Display device.

Claims (1)

[Claims] 1. A heating means for heating a terminal of a component soldered to a circuit board, a temperature measuring means for measuring the temperature of the terminal heated by the means, and a solder or circuit soldered to the terminal. A heating means for heating at least one of the patterns, a temperature measuring means for measuring the temperature of the solder or the circuit pattern heated by the means, and a sum of the temperature of the terminal and the temperature of the solder or the circuit pattern is calculated. And a means for comparing the sum of the temperatures with the sum of the temperatures in a normal soldering state obtained in advance to determine whether the soldering state of the terminal is good or bad. Inspection device.