JPS59122970A - Apparatus for detecting solder bridge between lead terminals of electronic parts - Google Patents

Abstract

PURPOSE:To attain to shorten a detecting time by enabling the automation in the detection of a solder bridge, by detecting the presence or absence of the solder bridge between lead terminals by measuring voltage corresponding to the resistance between the lead terminals. CONSTITUTION:The respective solder parts of lead terminals 2, 3 of a switch are connected to a constant-current circuit through contact pins 10, 11 and the voltage between the terminals 2, 3 is measured through contact pins 16, 17 and an A/D converter 22. The presence or absence of the solder bridge 5 is automatically detected regardless of the state of a movable contact piece on the basis of the voltage corresponding to the resistance value between the terminals 2, 3 changed corresponding to the presence or absence of the solder bridge 5 and the contact or not of the movable contact piece 6. By this constitution not requiring the change-over of the contact piece, the detection of the solder bridge can be automated and the detecting time of the solder bridge is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solder bridge detection device between lead terminals of an electronic component, in which a constant current is supplied between points on a pattern to which respective lead terminals to be measured are connected. By detecting the potential difference between the lead terminals and measuring the resistance value, the presence or absence of a solder bridge between the lead terminals can be detected.For example, the presence or absence of a solder bridge between the lead terminals of a switch can be detected without changing the connection position of the switch. To provide a device for detecting solder bridges between lead terminals of electronic components, which eliminates the need for the process of changing the connection position of a switch, automates the process of inspecting printed circuit board circuits, and shortens inspection time.

Generally, electronic components are soldered onto a printed circuit board, and a printed circuit board circuit is inspected on a platform. During soldering, a contact bin is brought into contact with the part, and two contact bins, for example, are selected from each of the contact bins. A current is passed through a single electronic component, and the voltage during this time is measured to inspect the constants of each electronic component and the wiring pattern for short circuits, etc.

Here, a switch 1 on a printed circuit board as shown in FIG. 1 may produce a solder bridge 5 between its lead terminals 2 and 3, resulting in a short circuit between the lead terminals 2 and 3. For this purpose, two lead terminals 2, 3, 3, 4, or 2.4 are sequentially selected from among the lead terminals 2.3.4 of the switch, and a current is passed between them and the voltage between these lead terminals is measured. The presence or absence of a solder bridge is inspected. If the lead terminals 2 and 3 to be inspected are in a conductive state by the movable contact piece 6, the presence or absence of a solder bridge between the lead terminals 2 and 3 is detected.
I can't do it. For this reason, conventionally, during the test of the switch, the connection position of the movable contact H was sequentially changed so that the lead terminals under test would not be electrically connected by the movable contact piece. Therefore, in printed circuit board circuits that have a large number of lead terminals and a large number of switching cycles, or are equipped with a large number of switches, the switching operation of the above-mentioned switches requires phase detection, and this switching operation process takes time. There was a drawback.

Here, the resistance value when the lead terminals are electrically connected by the solder bridge is about 1 mΩ or less, and the resistance value when the lead terminals are electrically connected by the movable contact piece is about 5 to 30 IIlΩ depending on the contact resistance. If the difference between these resistance values can be detected, the H
However, since there is contact resistance between the lead terminal and the contact pin, it is not possible to measure the difference in resistance value through the contact pin even if a low resistance measuring device is used. It's impossible. Furthermore, since low-resistance measuring instruments require an AC constant current source as their signal source, the alternating current signals interfere between the four cables connecting the measuring instrument and the lead terminals of the switch, causing measurement errors. I can not use it.

It is also possible to use image processing technology to detect solder bridges between the lead terminals of a switch. In some parts of soldering, the white patterns overlap, making it difficult to distinguish them from solder bridges, and if solder bridges are minute, it is difficult to detect them.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described with reference to FIG. 2 and the following figures.

FIG. 2 shows a block system diagram of an embodiment of the apparatus of the present invention. In the same figure, 8 is a constant current circuit, which is composed of a DC voltage source 9 and a resistor Rs connected in series with the DC voltage source 9. A contact bin 10 is connected to one end of the resistor Rs by a lead wire 11, and a DC voltage source At one end of the source 11 is a contact bottle 1.
2 are connected by lead wires 13. Here C゛, when inspecting the presence or absence of a solder bridge between the lead terminals 2 and 3 of the switch 1 shown in the first diagram, contact bin 10゜12
Each is brought into contact with a solder hole 14, 15 on the solder surface of the printed circuit board shown in FIG. The printed circuit board shown in the third diagram corresponds to the switch 1 shown in the first diagram, and the lead terminals 2 and 3 of the soldered switch 1 are arranged in the soldering pattern 14. , 15, respectively.

Further, contact pins 16 and 17 are brought into contact with the lead terminals 2 and 3 of the switch 1, respectively. The contact bins 16, 17 are connected to the first . It is connected to the second input terminal. The differential amplifier 20 differentially amplifies the voltages applied to the nineteenth and second input terminals to obtain the differential voltage. This differential voltage is amplified by a DC amplifier 21, then converted into a digital value by an A/D converter 22, and supplied to a microcomputer 23, where it is compared with a predetermined value.

Here, the voltage of the DC voltage source 9 is set to 20■, and the resistance Rs is set to 1Ω.
When the contact pins 10 and 12 are shorted as shown in FIG. 1, the current i is 20 mA. In addition, contact bin 10,
Terminals 3 and 4 are the contact resistance and the resistance of the lead wires 11 and 13 when each of the soldered parts 14 and 15 comes into contact with each other.
The contact resistance when conductive by the movable contact piece 6 is usually 10 or less in total, and the fluctuation Δi of the above current i due to these resistances is 0.02111A or less, and the constant current circuit 8 has a fluctuation rate of 0.1% and a 20 m A constant current of A is supplied.

] When the contact pin 10.12 is brought into contact with the solder joint 14°15, if the lead terminals 2 and 3 do not have the solder bridge 5 and the movable contact piece 6, the resistance value between the lead terminals 2 and 3 is At infinity, current 1 does not flow, and the voltage between lead terminals 2 and 3 is 20V.

Next, when the lead terminals 2 and 3 are electrically connected by the movable contact piece 6 and there is no solder bridge 5, the current i flows and the contact resistance due to the movable contact piece 6 between the lead terminals 2 and 3 is reduced to 10, for example.
If it is mΩ, the voltage drop across 2.3 lead terminals is 0.2m.
It becomes V. In addition, when there is a solder bridge 5 between the lead terminals 2 and 3, the voltage drop between the lead terminals 2 and 3 is equal to the resistance value between the lead terminals 2 and 3 caused by the solder bridge 5 of 1 m.
Since it is Ω or less, it is 0.02 mV or less.

The voltage between the lead terminals 2 and 3 is converted into a differential voltage by the differential amplifier 20, and the digital value is input to the microcomputer 2.
The microcomputer 23 stores a digital value of a reference voltage corresponding to a voltage of 0.1 mV in its built-in memory, and this lead terminal 2
9. During the inspection between 3 and 3, the digital value of the differential voltage and the digital value of this reference voltage are compared and discriminated, and the differential voltage is lower than the reference voltage.9. When the value is high, it is assumed that there is no solder bridge, and information about the presence or absence of a solder bridge is written to the memory.

The circuit configuration for this test is represented by the equivalent circuit shown in FIG. Contact resistance of L2 R+, R
2 and the resistances R3 and R4 of the lead wires 11 and 13 can be almost ignored as described above, and when the lead terminals 2 and 3 are electrically connected by the movable contact piece 6 or the solder bridge 5, A current i from the constant current circuit 8 flows through the resistor RX between them. In addition, the input impedance Rs and R6 of the differential amplifier 20 are replaced by the contact resistances R7 and Ra of the contact bins 16 and 17 and the resistances R9 and RIG of the lead wires 18 and 19.
Compared to -C, the contact resistance of this contact bottle 16.
．． The resistors R9 and RlO of the differential amplifier 20 can be ignored. The potential of the second input terminals is equal to the potential of the lead terminal 2.3. For this reason, lead terminal 2,
In the conventional method, a contact bin is brought into contact with each of the three contact bins, a constant current is passed between them, and the voltage between the contact bins is measured. Contact resistance R+, R
The voltage drop Rx-1 between the contact bins, which could not be measured accurately due to the voltage drop caused by 2, can be measured with high accuracy, and it is possible to distinguish between the resistance value due to the solder bridge and the resistance value due to the movable contact piece. be. Therefore, it is not necessary for the movable contact piece 6 of the switch 1 to switch the lead terminal 3.4 into conduction. During this inspection, the contact pins 10.12 on the constant current circuit 8 side may be brought into contact with the wiring patterns connected to the lead terminals 2.3, but the contact pins 10.12 on the differential amplifier 20 side .17 must be in contact with lead terminals 2 and 3, respectively.

After the inspection between the lead terminals 2 and 3, a relay (not shown) is switched by the microcomputer 23, and the soldered contact pin 10 connected to the lead terminal 4 in the wiring pattern is connected to the part 24. The presence or absence of a solder bridge between the lead terminals 3 and 4 is detected by switching the contact bin 16 to the contact 1-bin that is in contact with the lead terminal 4. - The presence or absence of solder bridges between the lead terminals of all the switches provided on the printed circuit board circuit is then detected in the same manner.

In this way, the complicated and time-consuming process of switching the connection position of the movable contact piece during inspection of the switch can be eliminated.

After the switch is inspected, it goes without saying that other electronic components of the printed circuit board circuit are inspected as usual.

In addition to switches, it is also possible to detect solder bridges between lead terminals of electronic components that have an internal DC resistance value and whose lead terminals are narrowly spaced, such as IFT (intermediate frequency transformer) coils and volume regulators. Not limited to implementation.

As described above, the solder bridge detection device between the lead terminals of an electronic component according to the present invention detects the resistance value between the lead terminals of an electronic component that is soldered to the wiring pattern of a printed circuit board and is in a conductive state internally. To perform the measurement, a direct current is supplied between the points on the wiring pattern to which the lead ends to be measured are connected, the voltage between the measurement lead terminals is detected, and the resistance between the lead terminals is measured. In order to detect the presence or absence of a solder bridge between lead terminals by distinguishing the difference between the resistance value 1 = resistance value through the inside of the electronic component and the resistance value through the solder bridge between the lead terminals, for example, the movable contact piece of the switch is It is possible to detect the presence or absence of solder bridges between the switch lead terminals even when the switch is in a different connection position. Therefore, the switching operation process of changing the connection position of the switch is no longer necessary, and the inspection process of printed circuit board circuits can be completely completed. It has the advantage of being automated and shortening the inspection time.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway side view of an example of a switch, Fig. 2 is a block diagram of an embodiment of the device of the present invention, and Fig. 3 is a half-lu of an example of a printed circuit board circuit to which the device of the present invention is applied. FIG. 4 is an equivalent circuit diagram of a portion of FIG. 2. 1...Switch, 2-4...Lead terminal, 5...
Solder bridge, 6... Movable contact piece, 8... Constant current circuit, 9... DC voltage source, 1.0.12.16.17...
・Contact bottle, 11, 13, 18. 19... Lead wire, 14. 15. 24... Solder (=J[pu part, 2
o... Differential amplifier, 21... DC amplifier, 22...
・A/D...Converter, 23...Micro Combi Coater. Procedural amendment dated February 24, 1980 1, Case indication 1982 Patent Application No. 229584 2, Title of invention Solder bridge detection device between lead terminals of electronic components 3, Person making the amendment Patent Applicant Address Tatami 221 3-12 Moriya-cho, Kanayō-ku, Yokohama, Kanagawa Prefecture Name (432) Japan Victor Co., Ltd. Representative Tori Hi+Yaku President Shishi Michi Part 6 Unrepresented, details of the invention in the specification subject to amendment Explanatory blinds and drawings. Contents of Z correction (1) In the specification, "11" in the second line of page 5 is corrected to "9". (2) r3, 4J in the seventh line of page 6 is corrected to r2.5J. (6) Amend Figure 2 of the drawings so that it can be written in red on the attached copy of the drawings.

Claims (1)

[Claims] Solder the lead terminals to the wiring pattern on the printed circuit board 1
To measure the resistance value between the wire terminals of an electronic component that has been connected to the wire and is in a conductive state internally, a direct current is supplied to the measurement lead between the points on the wiring pattern to which each wire terminal is connected. Detect the voltage between the lead terminals to be measured, measure the resistance between the lead terminals, and measure the difference between the resistance value through the inside of the electronic component and the resistance value through the solder bridge between the lead terminals. 1. A device for detecting solder bridges between lead terminals of electronic components, which detects the presence or absence of solder bridges between the lead terminals.