JPH1114574A - Soldering inspection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an inspection accuracy by heating a measurement surface located near the terminal of a substrate, measuring temperature, and judging whether soldering is appropriate or not from the obtained temperature data. SOLUTION: Laser beams L being emitted from a pulse laser 13 based on a signal from a trigger device 11 heats the measurement surface of a substrate body 21 around the junction part between a lead 32 and a terminal 22 and the measurement surface of the substrate body 21 around the terminal 22. At the same time, the temperature of the substrate body 21 that is heated by a thermoviewer 14 starts to be measured. When the junction between the lead 32 and the terminal 22 is improper, heat at a temperature measurement part simply escapes to the substrate body 21, so that heat easily stays. Therefore, the maximum temperature increases as compared with a case where soldering is being made appropriately and at the same time a cooling speed is delayed. In this manner, the maximum temperature or the cooling temperature at the temperature measurement part is measured and is compared with a predetermined threshold, thus judging whether soldering is appropriate or not.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering inspection method and a soldering inspection apparatus for performing a soldering inspection of an electronic component mounted on a substrate in a non-contact manner.

[0002]

2. Description of the Related Art There are known several soldering inspection methods for inspecting the quality of soldering of an electronic component mounted on a board in a non-contact manner. For example, there are known a method of analyzing vibration of a lead when vibration is applied, a method using X-rays, a method using eddy current, and the like.

The method of applying vibration is a method in which a target lead is blown using air, and the vibration of the observed lead portion is confirmed by laser speckle. Other known methods include blowing a lead with air and detecting the vibration of the lead by heterodyne with an optical probe. The method using the lead vibration is an excellent method in view of the fact that the bonding strength can also be measured. However, there is a limitation that the inspection can be performed only on a lead having a shape that easily vibrates as an inspection target.

In the method using X-rays, transmission observation of a soldered portion is performed using a micro X-ray source.
Since the target portion is regarded as a mere “shadow”, it is impossible to inspect the true bonding state, and it is insufficient to actually inspect the presence or absence of soldering.

[0005] The method using eddy current is a powerful method that can measure the electrical conductivity of the joint portion by using the inductance change of the sensor coil due to the eddy current generated in the inspection portion. However, there are problems that the sensor has one surface of the displacement sensor and that the measurement spatial resolution cannot be reduced. In the eddy current method, the positioning accuracy of the sensor is severe, and this is a problem.

On the other hand, the soldering inspection method utilizing heat conduction does not have the drawbacks of the other soldering inspection methods described above. In this method, the behavior of heat that heats the leads of the electronic components mounted on the board and escapes from the leads to the terminals of the board,
For example, the quality of soldering is inspected by observing the cooling rate using a thermoviewer or the like that detects radiated infrared rays.

That is, if the lead and the terminal are sufficiently bonded, the heat of the lead can easily escape to the terminal.
If the cooling rate is high and the connection between the lead and the terminal is insufficient, the heat of the lead is difficult to escape and the cooling rate is low. In addition, if the lead has a void structure, the maximum temperature increases, so that a defect can be detected.

[0008]

The above-mentioned conventional soldering inspection method utilizing the thermal conduction of the leads has the following problems. That is, the emissivity of the lead greatly changes depending on the surface condition of the lead, the color of the solder, and the like.
Further, since the radiated infrared rays have directivity, the emissivity is apparently different even when the lead is inclined or in a different posture. Therefore, even when the same type of lead is used, the maximum temperature and the cooling rate are different, so that the inspection result is affected, and there is a problem that an accurate pass / fail judgment cannot be performed.

Accordingly, the present invention provides a method for inspecting the quality of soldering of an electronic component mounted on a substrate by a non-contact method using heat conduction. It is an object of the present invention to provide a soldering inspection method and a soldering inspection device capable of performing a high-accuracy pass / fail determination without being affected by variations in emissivity due to the above.

[0010]

In order to solve the above-mentioned problems and to achieve the object, the invention according to claim 1 is directed to a joint between a lead of an electronic component mounted on a substrate and a terminal of the substrate. In a soldering inspection method for inspecting the quality of soldering, a heating step of heating a measurement surface located near the terminal of the substrate, a measurement step of measuring the temperature of the measurement surface, Determining whether the soldering is good or bad from the temperature data obtained.

According to a second aspect of the present invention, in the first aspect of the present invention, it is preferable that in the measuring step, the temperature is measured without contact by a thermoviewer.
According to a third aspect of the present invention, in the first aspect of the present invention, it is preferable that the determining step is to determine based on a maximum temperature of the measurement surface.

According to a fourth aspect of the present invention, in the first aspect of the present invention, it is preferable that the determining step determines based on a cooling rate of the measurement surface. An invention according to claim 5 is a soldering inspection device for inspecting the quality of soldering at a joint between a lead of an electronic component mounted on a substrate and a terminal of the substrate. A heating unit that heats the measurement surface located, and a measurement unit that measures the temperature of the measurement surface,
A determination unit for determining the quality of soldering based on the temperature data obtained by the measurement unit is provided.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, it is preferable that the measuring section includes a thermoviewer for detecting the temperature of the measurement surface in a non-contact manner.

According to a seventh aspect of the present invention, in the fifth aspect of the present invention, it is preferable that the determination unit determines the quality of the soldering based on the maximum temperature of the measurement surface.

According to an eighth aspect of the present invention, in the fifth aspect of the invention, it is preferable that the determination section determines the quality of the soldering based on a cooling rate of the measurement surface.

As a result of taking the above measures, the following operation occurs. That is, according to the first aspect of the present invention, the measurement surface located near the terminal of the substrate is heated, the temperature of the measurement surface is measured, and the quality of the soldering is determined from the temperature data obtained at this time. I have to. Therefore, temperature data of the substrate having a stable emissivity can be obtained, and accurate measurement can be performed.

According to the second aspect of the present invention, since the temperature is measured by the thermo-viewer in a non-contact manner, the temperature can be measured without giving an error to the measurement result.
According to the third aspect of the invention, by measuring the maximum temperature of the measurement surface, when the temperature is equal to or higher than the predetermined temperature, it is possible to determine that the soldering at the joint is defective.

According to the fourth aspect of the present invention, by measuring the cooling rate of the measurement surface, it is possible to determine that the soldering at the joint is defective if the cooling rate is lower than a predetermined rate.

According to the fifth aspect of the present invention, the measurement surface located near the terminal of the substrate is heated, the temperature of the measurement surface is measured, and the quality of the soldering is determined from the temperature data obtained at this time. Like that. Therefore, temperature data of the substrate having a stable emissivity can be obtained, and accurate measurement can be performed.

According to the invention described in claim 6, since the temperature is measured by the thermo-viewer in a non-contact manner, the temperature can be measured without giving an error to the measurement result.
According to the invention described in claim 7, by measuring the maximum temperature of the measurement surface, when the temperature is equal to or higher than the predetermined temperature, it can be determined that the soldering at the joint is defective.

In the invention described in claim 8, by measuring the cooling rate of the measurement surface, it is possible to judge that the soldering at the joint is defective if the cooling rate is lower than a predetermined rate.

[0022]

FIG. 1 is a view showing a configuration of a soldering inspection apparatus 10 according to an embodiment of the present invention, and FIG. 2 is a view showing a board 20 and an electronic component 30 to be inspected by the soldering inspection apparatus 10. FIG.

The soldering inspection device 10 includes a trigger device 11 for determining the timing of measurement, an LD controller 12 connected to the trigger device 11, and a pulse laser connected to the LD controller 12 and emitting a laser beam L for heating. 13, a thermo-viewer 14 for detecting the temperature of the soldering point in a non-contact manner, a sensor amplifier 15 for amplifying a signal from the thermo-viewer 14, and connected to the sensor amplifier 15 and to the trigger device 11. A frame grabber 16 and a computer 17 connected to the frame grabber 16 are provided.

In FIG. 1, reference numeral 20 denotes a mounting board, and 30 denotes a QF.
1 illustrates a P (quad flat package) type electronic component. The mounting board 20 includes a board body 21 and a plurality of terminals 22. Also, the electronic component 30
It has a component body 31 and a plurality of leads 32 each soldered to the terminal 22.

For the temperature measurement in the thermoviewer 14, the Stefan-Boltzmann law is used. That is, the electromagnetic wave intensity W from the heated temperature measuring point P on the substrate main body 21 is proportional to the output of the thermoviewer 14, and this value has the following relationship with the temperature of the measuring point P.

[0026]

(Equation 1)

Where C1 and C2 are wavelength-dependent constants,
T indicates the absolute temperature (° K) of the black body, λ indicates the wavelength, σ indicates the Stefan-Boltzmann constant, and ε indicates the emissivity of the substrate body 21. Here, ε is measured in advance for accurate temperature measurement of the substrate main body 21.

The soldering inspection apparatus 10 configured as described above inspects the quality of soldering as follows. That is, the laser light L emitted from the pulse laser 13 based on the signal from the trigger device 11 is indicated by a two-dot chain line G in FIG.
As shown in the figure, the joint between the lead 32 and the terminal 22 and the substrate body 21 around the terminal 22 are heated for a predetermined time. In addition,
The reason why the heating area is provided in both the lead 32 and the substrate body 21 is simply to facilitate heating.

At the same time, measurement of the temperature of the heated substrate body 21 by the thermoviewer 14 is started. And
An image is sent to the computer 17 every time a predetermined time elapses. In addition, image processing for emissivity correction, various corrections, etc. are performed as needed.

In FIG. 3A and FIG. 3B, P indicates a temperature measurement point by the thermo viewer 14. Here, if the lead 32 and the terminal 22 are satisfactorily joined, the heat at the temperature measurement point P escapes to the other part of the substrate body 21 indicated by the arrow α in FIG. As shown in FIG.
1 or to another part of the substrate body 21. Therefore,
The maximum temperature at the temperature measurement point P decreases, and the cooling rate also increases.

On the other hand, if the connection between the lead 32 and the terminal 22 is defective, the heat at the temperature measurement point P is only the heat that escapes to the substrate body 21 indicated by the arrow α in FIG. It will be easier. Therefore, the maximum temperature is higher than when the soldering is performed well, and the cooling rate is lower.

As described above, the maximum temperature or the cooling rate at the temperature measurement point P is measured, and the quality of the soldering is determined by comparing the maximum temperature or the cooling rate with a predetermined threshold value. On the other hand, the substrate body 2
1 has different emissivity depending on the material, but if the material used is limited, the emissivity is almost constant and there is little variation between samples. In addition, since the surface color of the substrate body 21 is usually green, the emissivity is larger than that of the soldering surface, and the S / N ratio is 4 to 5 times that of the case where the leads 32 are measured. Is possible. Furthermore, since the substrate body 21 has better flatness than the leads 32, there is no difference in the directivity of the emitted infrared rays.

Therefore, the measurement error can be minimized as compared with the case where the temperature of the lead 32 is measured. FIG.
Is a diagram showing a modification of the embodiment described above. That is, in the present modification, the line sensor 40 is used instead of the above-described thermo-viewer 14. Line sensor 40
Is constituted by arranging the temperature sensors 41 in an array type. In addition to such a line sensor 40, a stand-alone point sensor may be used.

The present invention is not limited to the above embodiment. That is, in the above embodiment, a laser beam is used as a heating source, but the present invention is not limited to this. Although a thermo-viewer and a line sensor are used as the measuring unit, a temperature sensor such as a single point-type sensor may be used. Further, although the determination unit makes the determination using the cooling rate and the maximum temperature of the lead, the rate of change such as the differential coefficient of the heating / cooling cycle may be used. Furthermore, QFP is used as an electronic component, but TCP (tape-carrier pack) is used.
Kage) can be applied to other types of electronic components. The measurement error may be further reduced by providing the pulse laser 13 with a means such as a kaleidoscope for keeping the irradiation intensity constant. In addition, it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0035]

According to the first aspect of the present invention, the measuring surface located near the terminal of the substrate is heated, the temperature of the measuring surface is measured, and the temperature data obtained at this time is used for soldering. The pass / fail is determined. Therefore, temperature data of the substrate having a stable emissivity can be obtained, and accurate measurement can be performed.

According to the second aspect of the present invention, since the temperature is measured by the thermo-viewer in a non-contact manner, the temperature can be measured without giving an error to the measurement result. According to the third aspect of the invention, by measuring the maximum temperature of the measurement surface, when the temperature is equal to or higher than the predetermined temperature, it can be determined that the soldering at the joint is defective.

According to the fourth aspect of the invention, by measuring the cooling rate of the measurement surface, it is possible to determine that the soldering at the joint is defective if the cooling rate is lower than a predetermined rate. it can.

According to the fifth aspect of the present invention, the measurement surface located near the terminal of the substrate is heated, the temperature of the measurement surface is measured, and the quality of the soldering is determined from the temperature data obtained at this time. The decision is made. Therefore, temperature data of the substrate having a stable emissivity can be obtained, and accurate measurement can be performed.

According to the sixth aspect of the present invention, the temperature is measured without contact by the thermoviewer, so that the temperature can be measured without giving an error to the measurement result. According to the invention described in claim 7, by measuring the maximum temperature of the measurement surface, when the temperature is equal to or higher than the predetermined temperature, it can be determined that the soldering at the joint is defective.

According to the invention described in claim 8, by measuring the cooling rate of the measurement surface, it is possible to determine that the soldering at the joint is defective if the cooling rate is lower than a predetermined rate. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a soldering inspection device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a board and electronic components to be inspected by the same device.

FIG. 3 is a view showing a principle of determination by the device.

FIG. 4 is a view showing a modification of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Soldering inspection apparatus 13 ... Pulse laser 14 ... Thermo viewer 17 ... Computer 20 ... Substrate 21 ... Substrate main body 22 ... Terminal 30 ... Electronic component 32 ... Lead 40 ... Line sensor

Claims (8)

[Claims] In a soldering inspection method for inspecting the quality of soldering at a joint between a lead of an electronic component mounted on a substrate and a terminal of the substrate, a measuring surface of the substrate located near the terminal is provided. A soldering inspection method, comprising: a heating step of heating; a measurement step of measuring the temperature of the measurement surface; and a determination step of determining the quality of soldering from the temperature data obtained in the measurement step. . 2. The soldering inspection method according to claim 1, wherein in the measuring step, the temperature is measured in a non-contact manner by a thermoviewer. 3. The method according to claim 1, wherein the determining step is based on a maximum temperature of the measurement surface.
Inspection method described in 1. 4. The method according to claim 1, wherein the determining step is performed based on a cooling rate of the measurement surface.
Inspection method described in 1. 5. A soldering inspection apparatus for inspecting the quality of soldering at a joint between a lead of an electronic component mounted on a substrate and a terminal of the substrate, wherein a measuring surface of the substrate located near the terminal is provided. A soldering inspection device comprising: a heating unit for heating; a measurement unit for measuring the temperature of the measurement surface; and a determination unit for determining the quality of the soldering from the temperature data obtained by the measurement unit. . 6. The soldering inspection apparatus according to claim 5, wherein the measurement unit includes a thermoviewer that detects a temperature of the measurement surface in a non-contact manner. 7. The soldering inspection apparatus according to claim 5, wherein the determination unit determines the quality of the soldering based on a maximum temperature of the measurement surface. 8. The soldering inspection apparatus according to claim 5, wherein the determination unit determines the quality of the soldering based on a cooling rate of the measurement surface.