JPS62237346A - Soldering inspection device for surface packaging component - Google Patents

Abstract

PURPOSE:To detect even a part which is not soldered securely although connected electrically by utilizing heat conduction to detect a defectively soldered part. CONSTITUTION:Terminals 2a of an electric component are fixed to the copper foil pattern 1a of an electric circuit board 1 by soldering 3. A heating means 4 which heats solder 3 is provided on the opposite side of the substrate 1 from the component 2. A temperature measuring means 5 which measures the surface temperature of the terminal parts to be soldered without contacting is provided on the fitting surface side of the substrate 1 for the component 2. The output of the means 5 is connected to a decision means 6. Then when heat rays are irradiated from the reverse surface of the substrate 1 by the means 4, the solder 3 is heated through the pattern 1a of the substrate 1. The means decides whether the soldering is normal or not from the heat conduction state of the solder a certain time after the start of said heating. Thus, even a part which is electrically connected but not securely soldered can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application) The present invention relates to a soldering inspection device for surface mount components that performs reflow soldering of components arranged on the surface of an electric circuit board.

(Prior Art) Conventionally, electrical components soldered to electrical circuit boards have been electrically inspected. In this method, an in-circuit board tester applies a voltage between two or more soldered points, and determines whether the product is good or bad based on the magnitude of the amount of current flowing.

(Problem to be solved by the invention) However, in the above-mentioned electrical inspection, even if the soldering is incomplete and only a small part of the solder is attached, or if there is no solder at all and there is simply contact, the electrical There was a risk that the product would be judged as non-defective because it was electrically conductive. Particularly in glue-flow soldering for surface mount components, in which a flexible printed circuit board is used as an electrical circuit board, components are lined up on the board, and terminals are soldered using a reflow method. In some cases, the welded parts of the parts were destroyed, and electrical continuity could no longer be established. Therefore, even if the board passes inspection, defects often occur due to bending of the board during storage.

The present invention has been made in view of the above-mentioned conventional drawbacks, and is a surface mount component that can inspect not only whether electrical continuity is established but also whether the terminals of electrical components are securely fixed by soldering. The purpose of the present invention is to provide a soldering inspection device.

(Means and effects for solving the problems) The configuration of the present invention will be explained using FIG. 1.

Terminals 2a of an electrical component 2 are fixed to the copper foil pattern 1a of the electrical circuit board 1 with solder 3. A heating means 4 for heating the solder 3 by irradiating heat rays such as infrared rays is provided on the opposite side of the circuit board 1 from the electrical components 2. Also board 1
Temperature measuring means 5 is provided on the mounting surface side of the electrical component 2 for non-contactly measuring the surface temperature of the terminal portion to be soldered. The output of the temperature measuring means 5 is connected to a determining means 6 for determining the quality of soldering.

Next, the operation of the present invention configured as described above will be explained. When the heating means 4 irradiates heat rays from the back surface of the substrate 1, the solder 3 is heated through the copper foil pattern 1a of the substrate 1.

After a certain period of time has elapsed from the start of heating, the heat conduction state is measured by the temperature measuring means 5, and based on this output, the determining means 6
determines whether the half-F opening is good or bad.

(Example) An example of the present invention will be described using FIGS. 2 to 6. A lamp 11 that emits a light beam containing infrared rays for heating is installed in a reflective umbrella 12 for evenly irradiating the flexible printed circuit board 15 to be inspected. An optical filter 13 is provided to cut out light in a wavelength range that increases the temperature of the substrate 15 when absorbed by the substrate 15. For example, if a polyimide film base or glass epoxy is used as the substrate 15, this wavelength range may be set to a longer wavelength side than about 800 nanometers. These lamps 11
, a reflector 12, and a filter 13 constitute a heating means 4.

A copper foil pattern 15affi is applied to the substrate 15, and an electrical component 16 is soldered onto this pattern 15a with solder 17 (see FIG. 4). This substrate 15 is placed on the support member 14, and the positioning bins 14a, 14b
is positioned. Support member 14 is copper foil pattern 1
It is made of a glass material that allows the heating light that heats the substrate 15 to pass through well, or a heat-resistant material that is perforated so that the back surface of the measurement portion of the substrate 15 is exposed. Said substrate 15
Above the side on which electrical components are attached (hereinafter referred to as the front side and the opposite side as the back side), heat rays generated from the solder 17 by irradiation with the lamp 11 are detected by a sensor array 21, which will be described later. A shutter 1B is provided to prevent this.

Above this, a mirror 1 is placed relative to the support member 14.
9 is installed obliquely at 45°. The right side of this mirror 19 (
(in the drawing) is provided with a mirror lens 20 as an optical system for projecting an image of the substrate onto a sensor array 21 constituting the temperature measuring means 5. The sensor array 21 is composed of a plurality of minute pyroelectric elements that sense heat rays such as infrared rays and convert them into electrical signals. A shielding mask 22 is provided on the mirror 19 side of the sensor array 21 to prevent thermal radiation from directly entering the sensor array.

Next, the determining means 6 which processes the output of the sensor array 21 to determine the soldering state will be explained with reference to FIG.

As described above, the sensor array 21 is made up of a plurality of micro pyroelectric elements, and each pyroelectric element is connected to the electrical scanning means 23. This scanning means 23 is connected via a buffer 7 amplifier 24 to an analog-to-digital (AD) converter 25, the output of which is connected to a memory 26. This memory 26
The output is input to a processor 27 that determines the soldering process state, and this processor 27 is also connected to the output of a memory 29 that stores good soldering patterns in advance. The determination output from the processor 27 is connected to a display device @30, so that the determination results are displayed.

The operation of one embodiment of the present invention constructed as described above will be explained with reference to FIGS. 4 to 6.

The circuit board 15 to be inspected is attached to the support member 14, and the lamp 11 is turned on. The copper foil pattern 15a is selectively heated due to the spectral characteristics of the filter 13, and the solder 17 is also heated due to heat conduction. When solder 17 gets hot,
Heat rays having wavelengths in the infrared region are emitted from the surface of the solder 17. Starting measurement of the surface temperature of the solder 17 using the sensor array 21 requires a certain amount of time for heat to be conducted, so it is preferable to measure the temperature a certain period of time after starting heating. For this reason, the shutter 18 is kept closed until the measurement is started, so as not to adversely affect the sensor array 21. After the predetermined period of time has elapsed, the shutter 18 is opened and the heat rays emitted from the surface of the solder 17 are reflected by the mirror 19 and imaged by the mirror lens 20 onto the sensor array 21 . The output of each micro pyroelectric element of the sensor array 21 is converted into a time series by the scanning means 23, converted into a digital signal by the AD converter 25 via the buffer amplifier 24, and stored in the memory 26. The processor 27 determines whether the soldering of the electrical circuit board 15 to be measured is good or bad based on the values stored in the memory 26 and the output pattern when the soldering is good stored in the memory 29, based on the criteria described later. Make a judgment. This determination result is displayed on the display device 30.

Next, the criteria for the determination made by the processor 27 will be explained. In a good soldering state, Fig. 4 (a)
), the terminal 16a of the electrical component 16 is completely covered with the solder 17. When the surface temperature of the solder 17 after heating is measured based on the output of the sensor array 21, an isothermal diagram having a peak at the center point 17a of the solder 17 as shown in FIG. 5(a) is obtained.

Further, if the temperature distribution is taken along the longitudinal direction (A-A') of the terminal 16a, a diagram as shown in FIG. 6 (a>) in which the temperature is plateau-like in regions x1 and x2 is obtained.

Next, regarding the defective soldering state, as shown in FIG. 4(b), only a small portion of the terminal 16a is soldered, and most of the terminal 16a is exposed. The temperature distribution on the surface of the solder 17 after heating this defective soldered board is an isothermal temperature distribution with a peak at a point 17b, which is slightly away from the center point 17a and where the terminal 16a is soldered, as shown in FIG. 5(b). Obtain a line diagram. This is because most of the terminal 16a is not covered with solder, and the only heat conduction is from the solder near the point 17b and through the air in the gap between the terminal 16a and the solder 17a, resulting in extremely poor heat conduction. be.

The longitudinal direction of the terminal 16a (B-
If you take the temperature distribution along the line B-), the peak will be at a point away from the center, as shown in Figure 6(b), and the temperature will be in the region x1.
It can be seen that the temperature is low at x2.

Another type of defective soldering is so-called bridging, where the solder in two places protrudes and becomes conductive.

About. The temperature distribution in this case is shown in FIG. 5(C). As can be seen from the figure, in this case terminal 16
t) The temperature distribution in the longitudinal direction is almost the same as that of a well-soldered board.

However, this is different from good soldering in that the solder portion that short-circuits the two terminals 16a and 16b is hotter than the surrounding area.

If the temperature distribution between the terminals 16a and 16b (C-CM) is drawn along the longitudinal direction of the terminals, it will be as shown in FIG. 6(C), with a peak of .degree. C.1.

To summarize the above state, the processor 27 is connected to terminal 1.
The temperature distribution is taken along the longitudinal direction of region x1.6a. x
If the temperature between the terminals 16a and 16b is low, it is determined to be defective, and if the temperature is high, then the temperature distribution is detected along the longitudinal direction between the terminals 16a and the adjacent terminals 16b. In order to improve the judgment that if a high temperature is detected, it is judged as defective, and if a low temperature is detected, it is judged as good, the area x1. Integrate the output of x2 (specifically, the area x1.x2
It is better to take the sum of the outputs between the two.

Next, another embodiment of the present invention will be described using FIG. 7.

A major difference is that the lamp 11 was used as the heating means 4 in the previous embodiment, whereas the laser 31 was used in this other embodiment.

The laser 31 uses, for example, a YAG laser with a wavelength of 1060 nanometers, is movable by a mechanical scanning member (not shown), and is provided with a focusing lens 32.

Further, a diaphragm 33 that moves together with the laser 31 is provided on the front side of the substrate 15. This diaphragm 33 is provided to allow only the heat rays generated by the laser beam to enter a pyroelectric element 34, which will be described later. As the temperature measuring means 5, a single pyroelectric element 34 is used instead of the sensor array 21, and the output changes according to the movement of the laser 31. Therefore, the electrical scanning means required in the previous embodiment is unnecessary. Since the configuration other than the above-described configuration is the same as that of the previous embodiment, the same parts are denoted by the same reference numerals and detailed explanations will be omitted.

The operation of another embodiment configured as above will be explained. The laser 31 is focused into a narrow beam by the lens 32, and the substrate 1 is
5. Heat the copper foil pattern from the back side. As a result, heat rays are emitted from the surface of the solder 17 as in the first embodiment, and are input to the pyroelectric element 34 via the aperture 33, mirror 19, and mirror lens 20. Since the laser 31 moves as described above, the output of the pyroelectric element 34 becomes a time-series signal. This signal is processed in the same manner as in one embodiment and is processed by the processor 2.
7, it is determined whether the soldering is good or bad.

If such a configuration is adopted, it will take time for inspection, but the sensor can be made of a single element, resulting in a relatively simple configuration. Furthermore, since a focused laser beam is used as a heating means, it is possible to detect minute parts. Furthermore, if the output of the laser beam is increased, reheating can be performed to correct defective soldering points, so there is an advantage that if a defective point is detected by inspection, it can be repaired immediately.

Although the above embodiment is configured to move the laser 31, the configuration is not limited to this. For example, the laser 31 may be fixed and the substrate 15 may be moved, or the lamp 11 of one embodiment may be used instead of the laser 31. Of course, the lamp 11 and the substrate 15 may be fixed and the mirror 19 may be rotated.

In the above description of the embodiments, the wavelength of the hot ray and the substrate material were selected so as not to heat the substrate while heating the copper foil pattern. This method selectively heats the copper foil pattern, so it can be inspected with extremely high accuracy; however, for boards with copper foil patterns on both sides, the humidity distribution may be tilted because heat is absorbed even on the back side pattern. There is. For such double-sided patterned substrates, it may be better to heat the substrate material for better accuracy.

(Effects) As described above, the present invention uses heat conduction to detect defective soldering points, so even if the electrical connection is established, it can also detect points that are not properly soldered. There are advantages to what you can do.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the concept of the present invention, Fig. 2 is a diagram showing the configuration of an embodiment of the invention, Fig. 3 is an electric circuit diagram showing an embodiment of the invention, and Fig. 4 (a) (b). 5(a), (b), and (c) are partially enlarged sectional views of one embodiment of the present invention.
) are planar temperature distribution diagrams of solder in one embodiment of the present invention.
FIG. 7 is a diagram showing another embodiment of the present invention. 1... Electric circuit board 2... Electrical component 3... Half 4... Heating means 5... Temperature measuring means 6... Sensing means Patent applicant Issued by Olympus Optical Industry Co., Ltd. 1) 1st Illustration ゝ, -〆Figure 2 Figure 312I Figure 4 Figure 5 Bill ℃Ne City Main Gate May 16, 1986 Mr. Uga Retirement, Commissioner of the Patent Office
1. Indication 11 of 1. Patent Application No. 80825 of 1961 2. Title of the invention: Soldering inspection device for surface mount components 3. Person making the correction (Hakko) (1) Description No. "Nishitara" written in line 9 of page 5,
Change it to "If the wavelength is transparent." (2) At the end of the 6th line on page 6, next to ``Provided.'', ``This shutter 18 is heated by heat rays from the heat source 4.''
This is to prevent the sensor array 21 from being heated by the heat rays that have passed through areas other than the copper foil pattern 15a while the solder 17 is being heated. ” is inserted. (3) The phrase “statement.” written in line 16 on page 10 will be corrected to “statement.” (4) "Peakro" described in page 11, line 5 of the same page is replaced with "
"The peak that exceeds the failure judgment threshold t1 at the position corresponding to the short circuit". (5) "According to movement" stated in page 12, line 14 of the same
is changed to "As the aperture 33, mirror 19, mirror lens 20, and pyroelectric element 34 move, the pyroelectric element 34 moves in accordance with this movement."

Claims (2)

[Claims] (1) In a soldering inspection device for surface mount components that performs reflow soldering by arranging components on the surface of an electric circuit board, a heating means that heats the electric circuit board by irradiating a hot ray or the like from the opposite side of the component mounting surface. and a non-contact temperature measuring means for measuring the surface temperature of a terminal portion of a component to be soldered from the component mounting surface side of the electric circuit board, and an output of the temperature measuring means after being heated for a certain period of time by the heating means. What is claimed is: 1. A soldering inspection device for surface mount components, comprising: determining means for determining whether soldering is good or bad based on . (2) The soldering inspection apparatus for surface mount components according to claim 1, wherein the determining means stores a temperature distribution pattern when soldering is good, and performs the determination by comparing it with this pattern. .