JPH0675061B2 - Soldering inspection method - Google Patents

Description

The present invention relates to a soldering inspection method.

[Conventional technology]

As a conventional technique, for example, there is a soldering inspection method disclosed in Japanese Patent Publication No. 60-8707.

The conventional soldering inspection method is configured to include means for irradiating the soldering surface with light conically focused by a convex lens, and means for imaging the soldering surface from above.

Next, a conventional soldering inspection method will be described in detail with reference to the drawings.

FIG. 3 is a schematic view showing an example of the conventional art, and FIG.
FIG. 4C is a perspective view showing the operation of the soldering inspection method shown in FIG.

The light a from the light source 101 is condensed by the projection lens 104, folded as projection light b, reflected by the mirror 105, and projected onto the solder surface 102 on the printed circuit board 106.

At this time, if the soldering is normal, a circular figure c is observed on the camera 103, if there is a dent in the solder, it is observed as a defective figure d ₁ , and if there is little solder, it is observed as a small area figure d _2. The quality of soldering is determined by the shape of the imaged figure.

[Problems to be solved by the invention]

In the above-described conventional soldering inspection method, since the quality of soldering is determined only from the outer shape of the soldered portion, it is not possible to know the connection strength of the soldered portion, and the defective product can be regarded as a good product. However, there is a drawback that it may be erroneously detected as a defective product.

[Means for solving problems]

The soldering inspection method of the present invention comprises a means for cooling the soldered connection portion, and a magnetic transformation of the first alloy layer of the soldered connection portion caused by cooling of the connection portion, and then the first alloy layer of the first alloy layer. Means for measuring magnetic characteristics, means for measuring magnetic characteristics of the second alloy layer after magnetic transformation of the second alloy layer of the soldered connection portion by further cooling, and determination of solderability And a means for judging acceptability by comparing the magnetic characteristic with the threshold value.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a graph showing magnetic transformation of an alloy layer.

A chip resistor composed of the electrode 1 and the body 2 is soldered on the mounting pad 4 of the printed circuit board 5.

In the solder portion 3, an alloy layer 6 of the electrode 1 of the chip component and the solder and a alloy layer 7 of the solder and the mounting pad 4 having a thickness of several μm are formed. However, if soldering is not normal, the alloy layers 6 and 7 cannot be formed, or even if they are formed, the amount of the alloy layers is small.

Both the electrode 1 and the mounting pad 4 are made of a non-magnetic material of a copper-based alloy. However, since some additives are mixed in the solder during soldering, it is possible that the solder portion 3 is magnetic. Alloy layers 6 and 7 having a transformation point are generated.

The paramagnetic to non-magnetic transformation temperature T ₁ of the alloy layer 6 and the alloy layer 7
The paramagnetic to non-magnetic transformation temperature T _{2 of} is generally different.

While the temperature is lowered by the cooler 11, the magnetic sensors 8 use the paramagnetic magnetization temperatures TA ₂ and TB _{2 of the} nonmagnetic magnetization temperatures TA ₁ and TB ₁ respectively to obtain the magnetization amounts MA ₂ , MB ₂ , MA ₁ and MB ₁ of the solder portion 3. If you measure the alloy layer 6,7
The quantities Qa and Qb can be measured, and can be expressed by equations (1) and (2).

_{Qa = k (MA 2 -MA 1} ) ............ (1) Qb = k (MB 2 -MB 1) ............ (2) where k denotes the magnetization constant.

To judge the quality of soldering, the magnetization amount measured by the magnetic sensor 8 is amplified by the amplifier 9, converted into the amount of alloy by the judgment device 10, and then compared with a predetermined value. If the number is small, it is determined to be defective and output to the output terminal 12.

〔The invention's effect〕

In the soldering inspection method of the present invention, the amount of alloy can be directly obtained by measuring the amount of alloy between the electrode and the solder and the amount of alloy between the mounting pad and the solder, which can be obtained during good soldering, as the amount of magnetization. Therefore, there is an effect that the quality of soldering can be surely determined.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention, FIG. 2 is a graph showing the magnetic transformation of an alloy layer, FIG. 3 is a schematic view showing an example of the prior art, and FIG. 4 is a defect in FIG. It is a perspective view showing a detection example. 1 ... Electrode, 2 ... Body, 3 ... Solder part, 4 ... Mounting pad, 5 ... Printed circuit board, 6,7 ... Alloy layer,
8 ... Magnetic sensor, 9 ... Amplifier, 10 ... Judgment device, 11 ...
… Cooler, 12 …… Output terminal.

Claims (1)

[Claims] 1. A means for cooling a soldered connection portion, and a magnetic transformation of the first alloy layer of the soldered connection portion caused by cooling the connection portion, and then measuring a magnetic characteristic of the first alloy layer. Means for measuring the magnetic characteristics of the second alloy layer after magnetically transforming the second alloy layer of the soldered connection portion by further cooling, and a constant for determining the quality of soldering. And a means for judging acceptability by comparing the magnetic characteristic with the threshold value and the soldering inspection method.