JP3703042B2 - Detection method of foot float by IC in-circuit tester and foot presser - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of detecting a foot lift of an IC (integrated circuit) mounted on a printed circuit board using an in-circuit tester such as an XY method or a pin board method, and the foot presser.
[0002]
[Prior art]
Conventionally, a mounting board, that is, a printed circuit board on which a large number of electronic components are mounted and soldered, uses an in-circuit tester to appropriately contact the tip of the pin probe with a necessary measurement point of the board, and Presence / absence of the substrate is determined by electrically detecting the presence or absence, or by electrically measuring the characteristic value of each component. This type of in-circuit tester has a pin board type in which a fixture (pin board) as an inspection jig is placed on a measurement table on which a substrate to be inspected is placed, and an XY on a measurement table on which the substrate to be inspected is placed. There are some of the XY type in which units are installed.
[0003]
In the pin board method, the number of pin probes equal to the number of measurement points on the board to be inspected is provided on the board in correspondence with the positions of the measurement points, and each pin probe is mounted on the board to be inspected. In contact with each measuring point. On the other hand, in the XY system, a Z-axis unit movable in the Y-axis direction is provided on an arm movable in the X-axis direction, and one pin probe is supported by the Z-axis unit so as to be movable in the Z-axis direction. By controlling the XY unit, the pin probe is appropriately moved from above the substrate in the X-axis, Y-axis, and Z-axis directions, and sequentially contacts each preset measurement point. Therefore, the pin board type is suitable for measuring a large amount of the same substrate to be inspected, while the XY method is suitable for measuring a large number of types of substrates to be inspected. In general, a measuring pin probe having a sharp tip is used.
[0004]
When an in-circuit tester using these methods is used to inspect for poor contact between a pin (lead) and a pattern due to poor soldering of an IC mounted on a printed circuit board, that is, when the IC foot float is inspected, usually the IC pin and its pin The measurement pin probe is brought into contact with the pattern on the substrate to be soldered, and the resistance value indicating the conductive state between the pin and the corresponding pattern is measured to determine whether or not there is a foot lift. At that time, accurate probing is required for the pins of the IC.
[0005]
[Problems to be solved by the invention]
However, the pin pitch of the IC has been narrowed in recent years, and the fine pitch has become remarkable. Therefore, even if an in-circuit tester is used to inspect a foot lift for an IC with a narrow pin pitch, it is difficult to accurately set up a measuring pin probe having a sharp tip protruding on the pin. In particular, in order to increase the accuracy of foot float detection, it is necessary to measure the resistance value by the four-terminal method as shown in FIG. In the figure, 10 is an IC, 12 is a pin, 14 is a printed circuit board, and 16 is a wiring pattern. Further, 18 is a measuring section, 20 is a constant current source thereof, 22 is a DC ammeter, 24 is a DC voltmeter, and 26 is a measurement pin probe. In addition, since the tip of the measurement pin probe protrudes sharply, if it is pressed against an IC pin or pattern, a dent is scratched.
[0006]
The present invention has been made paying attention to such a conventional problem. First, it is easy to cope with finer pin pitch of the IC, and it is based on the in-circuit tester of the IC that can reduce the dent scratch. An object of the present invention is to provide a foot float detection method. It is another object of the present invention to provide a foot press suitable for use in a foot floating detection method using an IC in-circuit tester.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, the first embodiment of the IC in-circuit tester uses the in-circuit tester to detect the lift of the foot, and the in-circuit tester is used to determine the conduction state between the IC pin mounted on the printed circuit board and the corresponding pattern. The amount of electricity shown is measured, and the presence or absence of the IC foot lift is determined from the measurement result.
[0008]
At that time, one measurement pin probe is pressed against the pattern to be connected to the ground or power supply pin of the IC and the pattern to be connected to the input or output pin to be inspected, and between the patterns corresponding to the ground or power supply pin. Measure the quantity of electricity that indicates the state of conduction between the input or output pin to be inspected and the corresponding pattern, and press the insulating pressure probe against the ground or power supply pin and the input or output pin to be inspected. Then, an electric quantity indicating both conduction states between the pattern corresponding to the ground or the power supply pin and between the pattern corresponding to the input or output pin for inspection is measured, and the difference between the two electric quantities is compared with a threshold value.
[0009]
Also, the foot presser that uses the IC in-circuit tester for the second purpose to detect the foot lift and presses the IC ground or power pin and the input or output pin to be inspected is the IC ground or power pin or the device to be inspected. As an insulating pressure probe for pressing an input or output pin , at least two rod-like bodies having an insulating material are provided at the tip, and the base end portions of both insulating pressure probes are integrated with a support member. Bonding is preferred .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a diagram showing an arrangement relationship between a pin and a pattern at the time of an inspection of a foot lift of an IC of a measurement pin probe and a foot presser provided in an XY in-circuit tester to which the present invention is applied. In the figure, 28 is a U-shaped foot presser, 30 (30a, 30b) is a rod-shaped insulating pressure probe, and 32 is a rod-shaped support member that joins the base ends of both insulating pressure probes 30. .
[0011]
The foot presser 28 is used by being attached to the piston rod tip 34 of an air cylinder (not shown) installed in the Z-axis unit of the XY unit. Then, a pressure is applied to the pair of pins 12 to be inspected by the corresponding probe 30 at the time of the foot float inspection of the IC 10. Therefore, it is necessary for both the pressurizing probes 30 to make at least the tip portions 36 (36a, 36b) insulative, and when using a U-shaped metal rod for the foot presser 28, both the tip portions 36 are made of an insulating material. Respectively. At that time, if the tip of the metal rod is flattened or an insulating material such as rubber is used as the insulating material, the pin 12 is hardly scratched. Further, the entire foot presser can be formed of an insulating material such as plastic. In FIG. 1, the numbers used in the description of the conventional example are used for the corresponding parts.
[0012]
When inspecting the foot float of the IC 10 using such an XY in-circuit tester having the measurement pin probe 26 and the foot retainer 28, first, the pattern 16a to which the ground (GND) pin 12a of the IC 10 is to be connected. The measurement pin probe 26 (26a, 26b) is pressed against the pattern 16b to which the one input or output pin 12b selected for inspection is to be connected. The measurement pin probe 26 can be operated as a piston rod of an air cylinder.
[0013]
Then, a constant current is supplied from the constant current source 20 to the IC 10 through both measurement pin probes 26. Then, as shown in FIG. 2, the parasitic diode 38 (38a, 38b) always exists between the ground pin 12a and each of the many existing input or output pins 12b (12b1, 12b2). Current flows. At that time, if the ground pin 12a is in a floating state and is away from the corresponding pattern 16a, no current flows, but the input or output pin 12b for inspection is in the floating state, and the corresponding pattern Even if they are separated from 16b, a current flows between the ground pin 12a and each pattern 16 because parasitic diodes related to other plural input or output pins 12b are usually connected in parallel. In FIG. 2, only two input or output pins 12b are illustrated.
[0014]
Therefore, the voltage meter 24 measures the voltage value V1 shown both conduction state between the ground pins 12a and corresponding between and inspected for input or output pin 12b of the pattern 16a and the corresponding pattern 16b. Next, the foot presser 28 is lowered, and the insulating pressurizing probe 30 is pressed against the ground pin 12a and the input or output pin 12b for inspection. Then, even if the ground pin 12a and the input or output pin 12b to be inspected are in a floating state, the pins 12a and 12b come into good contact with the corresponding patterns 16b.
[0015]
Again, a constant current is caused to flow from the constant current source 20 to the IC 10 through both measurement pin probes 26, and the pattern 16b corresponding to the input or output pin 12b to be inspected or between the pattern 16a corresponding to the ground pin 12a by the voltmeter 24. Measure a voltage value V2 indicating a state of electrical conduction between the two. Then, the difference between the two voltage values V1 and V2 is compared with a threshold value, and when the difference is larger than the threshold value, it is determined that the input or output pin 12b to be inspected is floating, and when the difference is small, there is no floating. And decide. When the ground pin 12a is floating, the voltage value V1 increases as it approaches infinity. Therefore, it is possible to determine whether the foot is floating by simply measuring the voltage value V1.
[0016]
In this way, when the foot lift 28 of the IC 10 is inspected using the foot retainer 28 including the two insulating pressure probes 30, there is no need to stand the measurement pin probe 26 on the pin 12, and the pin 12 Since it is only necessary to stand on the pattern 16 that is usually a little wider, it is possible to cope with the finer pin pitch of the IC 10 and to perform probing easily. Moreover, when such a foot presser 28 is provided with a mechanism for changing the distance between the probes of the both-insulating pressurizing probe 30 (not shown), the same foot presser 28 is used to provide a large number of each provided in the IC 10. It is more convenient because the foot float of the input or output pin 12b can be sequentially checked. In addition, each insulating pressurizing probe 30 may be made independent and operated separately.
[0017]
In the above-described embodiment, the measurement unit 18 includes the constant current source 20 and the DC voltmeter 24, and the voltage value is measured before and after pressing the ground pin 12a and the input or output pin 12b to be inspected by the both-insulating pressure probe 30. V1 and V2 were measured to determine whether the input to be inspected or the output pin 12b was lifted. The measuring unit 18 was equipped with a constant voltage source and a DC ammeter. Current values I1 and I2 are measured before and after the pin 12a and the input or output pin 12b are pressed, and the difference between the current values I1 and I2 is calculated and compared with a threshold value. It is also possible to determine whether or not the pin 12b is lifted.
[0018]
In the above-described embodiment, both insulative pressure probes 30 are used, and electric quantities such as voltage value and current value are measured before and after pressing the ground pin 12a and the input or output pin 12b to be inspected. However, since there is always a parasitic diode between the power supply (Vcc) pin and each input or output pin in the IC, both insulative processing is similarly performed. Using a pressure probe, the amount of electricity can be measured before and after pressing the power supply pin and the input or output pin to be inspected to determine whether or not the input or output pin to be inspected is lifted. However, the directionality of the parasitic diode existing between the power supply pin and the input or output pin is opposite.
[0019]
In the above embodiment, the insulating pressurizing probe 30 provided on the foot retainer 28 is pressed against the ground or power supply pin and the input or output pin to be inspected one by one. You may use the foot pressing tool provided with the insulation pressure probe which can be pushed.
[0020]
In the above-described embodiment, the method of detecting the foot lift of the IC 10 by the XY in-circuit tester has been described. However, the foot lift of the IC 10 can also be detected by the pin board in-circuit tester. In the latter case, the corresponding measurement pin probes provided on the pin board are pressed against the respective patterns 16 corresponding to all the pins 12 of the IC 10, and then the patterns corresponding to the ground or power supply pins and the input to be inspected. Alternatively, the quantity of electricity indicating both conductive states between the output pin and the corresponding pattern is measured.
[0021]
【The invention's effect】
According to the present invention described above, in the first aspect of the invention, when inspecting the floating of the IC, the measuring pin probe is pressed against a pattern that is usually slightly wider than the pin, and the pin is insulated. Since the pressure pressing probe is pressed, it is easy to set up a measurement pin probe and to cope with fine pitching of IC pins. In addition, the IC pin is not damaged.
[0022]
According to the second aspect of the present invention, the pattern to be connected to the ground or power supply pin and the pattern to be connected to the input or output pin to be inspected for each of the two insulating pressing probes provided in the foot presser In contrast, the number of XY units for operating the insulating pressure probe can be reduced.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing an arrangement relationship between pins and patterns when an IC foot float inspection of an IC of a measurement pin probe and foot retainer provided in an XY in-circuit tester to which the present invention is applied.
FIG. 2 is a diagram showing a parasitic diode existing between an IC ground pin and an input or output pin.
FIG. 3 is a diagram showing an arrangement relationship between pins and patterns when an IC foot float inspection is performed by a four-terminal method of a measurement pin probe provided in a conventional XY in-circuit tester.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... IC 12a ... Ground pin 12b ... Input or output pin 14 ... Printed circuit board 16 ... Pattern 18 ... Measurement part 20 ... Constant current source 24 ... Voltmeter 26 ... Measurement pin probe 28 ... Foot presser 30 ... For insulation pressurization Probe 32 ... support member 36 ... probe tip 38 ... parasitic diode

Claims (2)

Using an in-circuit tester, measure the amount of electricity indicating the conduction state between the IC pin mounted on the printed circuit board and the corresponding pattern, and use the in-circuit tester to determine whether the IC has lifted from the measurement result. In the floating detection method, one measurement pin probe is pressed against the pattern to be connected to the ground or power supply pin of the IC and the pattern to be connected to the input or output pin to be inspected, and corresponds to the ground or power supply pin. Measure the amount of electricity that indicates the continuity between the patterns to be inspected and between the input or output pins to be inspected and the corresponding patterns, and press the insulating pressure probe between the ground or power supply pin and the input or output pin to be inspected. Similarly, between the pattern corresponding to the ground or power supply pin and the pattern corresponding to the input or output pin for inspection Measuring the electrical quantity indicative of both conduction state between over emissions, feet floating detection method with the in-circuit tester of the IC, wherein the comparing the difference between the quantity of electricity that such a threshold. A foot presser for pressing an IC ground or a power supply pin and an input or output pin to be inspected for use in the method of detecting a foot float by an in-circuit tester of the IC according to claim 1. Insulating pressure probes that push the input or output pins are equipped with at least two rod-shaped bodies having an insulating material at the tip, and the base end portions of both insulating pressure probes are joined together via a support member. A foot retainer characterized by

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