JP3281164B2 - Foot Lift Detection Method Using IC In-Circuit Tester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a floating foot of an IC (integrated circuit) mounted and soldered on a printed circuit board using an in-circuit tester.

[0002]

2. Description of the Related Art Conventionally, a mounting board, that is, a printed circuit board on which various electronic components are soldered, is appropriately brought into contact with probes at necessary measurement points on the board by using an in-circuit tester. The quality of the substrate is determined by objective measurement. In particular, the one in which the XY unit is installed on the measuring table on which the substrate to be inspected is mounted is provided with a Z-axis unit movable in the Y-axis direction on the arm movable in the X-axis direction, and the Z-axis unit is Since the probe is movably supported in the Z-axis direction, when the XY unit is controlled, the probe is appropriately moved in the X-axis, Y-axis, and Z-axis directions from above the substrate, and each preset The measuring points can be sequentially contacted. Since a plurality of measurement points must be measured simultaneously for each part, a plurality of sets of XY units are usually provided in the XY type in-circuit tester.

[0003] When using such an in-circuit tester to inspect a contact failure between a pin and a pattern due to a poor soldering of an IC mounted and soldered to a printed board, that is, a foot lifting, as shown in FIG. Is used, and a dedicated probe 16 having a tip 10 made of a laminate of a metal electrode 12 and an insulator 14 is used. At the time of inspection, the tip 10 of the dedicated probe 16 is connected to the digital IC 18.
After the other regular probe 20 is brought into contact with the pattern 22 on the substrate, and the conduction state between the pin 24 and the pattern 22 is known, the AC constant voltage power supply 26 A constant voltage is applied in the meantime, the current is measured using the ammeter 28, and the presence or absence of foot lifting is determined based on the current value. At that time, the dedicated probe 16
And the main body of the digital IC 18 form a capacitor of several PF. Therefore, if the soldering between the pin 24 and the pattern 22 is good, the current value increases, but if the foot is floating, the current value decreases. Note that the ordinary probe 20 is entirely elongated to the tip, has a spring property in the axial direction, and applies electrical force by applying the tip to a measurement point and applying a static load.

[0004]

However, such a dedicated probe 16 is used only when inspecting the soldering state between the pins 24 of the IC 18 and the pattern 22 among various electronic components mounted and soldered on a printed circuit board. There is a problem because it is a dedicated tool to use. This is because the normal probe 20 is used when performing electrical measurements on other electronic components. Therefore, if the dedicated probe 16 is required only for the inspection of the floating of the IC 18, the burden on the inspection increases. Because. In particular, in the XY method in-circuit tester, the dedicated probe 16 must be attached to one set of the XY units only when inspecting the floating of the IC 18.
It takes time to exchange the normal probe 20 and the dedicated probe 16 that have been used until then. Therefore, the inspection cannot be sped up, which is inconvenient.

Incidentally, when an IC is mounted and soldered on a printed circuit board, the IC is connected between an independent pattern connecting at least one pin of the IC and the ground of the board, or
There is a floating capacitance between the independent pattern connecting at least one pin and the independent pattern connecting the other at least one pin.

The present invention has been made in view of such conventional problems, and has an independent pattern for connecting at least one pin of an IC mounted and soldered on a substrate and an independent pattern for connecting at least one other pin. The use of the stray capacitance existing between the IC and the IC eliminates the need for a dedicated probe for the IC and speeds up the inspection.
It is an object of the present invention to provide a method for detecting a foot lift using an in-circuit tester.

[0007]

In order to achieve the above object, in the method for detecting a floating foot and a bridge solder by an in-circuit tester of an IC according to the present invention, at least one pin 34 of an IC 30 mounted and soldered to a substrate is connected. After discharging the charge stored in the floating capacitance 46 existing between the independent pattern 42 and the ground 44 of the substrate, charging of the floating capacitance 46 with the DC constant current I0 is started, and during the transition period, The voltage V1 and V2 at the time when two different predetermined times t1 and t2 have elapsed after the start of charging are calculated, and the value C of the floating capacitance 46 is calculated. Judgment of the presence of foot lifting and bridge soldering by comparing with the calculated stray capacitance value C0 of the same location of the same IC where the other board is well soldered. That.

In another method for detecting a foot lift by an IC in-circuit tester according to the present invention, an independent pattern 68 for connecting at least one pin 60a of an IC 56 mounted and soldered to a substrate is connected to another at least one pin 60b. Floating capacitance 7 existing between independent patterns 70
After discharging the charge stored in 2, charging of the stray capacitance 72 with a DC constant voltage V 0 is started, and a current I 1 when a predetermined time t 0 elapses after the start of charging in the transition period is measured. After discharging the electric charge stored in the floating capacitance 72 again, charging of the floating capacitance 72 with the DC constant voltage V0 is started with the polarity reversed, and the same predetermined time t0 after the start of charging in the transition period is obtained. The current I2 at the lapse of time is measured, and the presence or absence of foot lifting is determined by comparing the current value I2 with the previously measured current value I1.

Further, in another method of detecting a leg buoy using an IC in-circuit tester according to the present invention, an independent pattern 68 connecting at least one pin 60a of an IC 56 mounted and soldered to a substrate is connected to another at least one pin 60b. After discharging the charge stored in the floating capacitance 72 existing between the independent pattern 70 and the floating capacitance 72,
With a constant DC current I0, a voltage V1 is measured when a predetermined time t0 elapses after the start of charging during the transition, and the electric charge stored in the floating capacitance 72 is discharged again. The charging of the stray capacitance 72 with the DC constant current I0 is started with the polarity reversed, and the voltage V2 at the same predetermined time t0 after the start of charging during the transition period is measured, and the voltage value V2 is measured. The presence or absence of foot lifting is determined by comparing with the voltage value V1 previously observed.

[0010]

In order to carry out the above method, at least one
The probes are respectively brought into contact with the independent pattern 42 connecting the pins 34 and the ground 44 of the substrate, and the electric charge stored in the floating capacitance 46 is discharged. Thereafter, the direct current constant current I to the stray capacitance 46 is passed through both probes.
Start charging with 0. Then, voltages V1 and V2 across the stray capacitance 46 when two different predetermined times t1 and t2 have elapsed after the start of charging in the transition period are measured. However, t1 <t2. Then, stray capacitance 4
6 is C = {I0 × (t2−t1)} / (V2−V
It can be calculated from the formula 1). Therefore, if the value C0 of the stray capacitance at the same location of the same IC in which the other board is well soldered is calculated in advance, the value C of the stray capacitance 46 is compared with C0. be able to. At this time, if the soldering of the pin 34 is defective and the foot is in a floating state, the value C of the floating capacitance 46 is reduced by 20 to 30% from C0. But,
When the pin 34 of the IC 30 is, for example, a bridge solder connected to the adjacent pin 56 by solder, the value C of the stray capacitance 46 is increased by 20 to 30% from C0. As a result, it becomes possible to determine whether or not there is a foot lift and the presence of bridge solder.

[0011] Also, when performing the other methods described above,
First, the probe is brought into contact with the independent pattern 68 connected to at least one pin 60a of the IC 56 and the independent pattern 70 connected to the other at least one pin 60b, and the electric charge stored in the stray capacitance 72 is discharged. Thereafter, a constant DC voltage V to the stray capacitance 72 is supplied through both probes.
Start charging by applying 0. Then, the current I1 flowing through the stray capacitance 72 when a predetermined time t0 has elapsed after the start of charging during the transition period is measured. Thereafter, the electric charge stored in the floating capacitance 72 is discharged again, and charging of the floating capacitance 72 with the DC constant voltage V0 is started with the polarity reversed, and a predetermined time t0 after the start of charging in the transition period elapses. Current I flowing through the stray capacitance 72 when
Measure 2. Therefore, the current values I1 and I2 can be compared. At this time, if all the pins 60 connected to both patterns 68 and 70 are soldered well,
Even if the direction of applying the constant voltage V0 is reversed, the stray capacitance 7
2 are equal, and the current values I1 and I2 are I1 = I2
= (CV0) / t0. However, if the soldering of some or all of these pins 60 is bad and the pins are in a floating state, the value C of the stray capacitance 72 becomes different if the direction in which the constant voltage V0 is applied is changed. The current values I1 and I2 are different. As a result, it is possible to determine the presence or absence of foot lifting only by inspecting the IC 56 mounted and soldered on the same substrate to be inspected.

Further, when the above-mentioned other method is carried out, first, the probe is brought into contact with the independent pattern 68 connected to at least one pin 60a of the IC 56 and the independent pattern 70 connected to the other at least one pin 60b. Then, the electric charge stored in the floating capacitance 72 is discharged. Thereafter, charging of the stray capacitance 72 with the DC constant current I0 is started via both probes. Then, the voltage V1 across the floating capacitor 72 is measured when a predetermined time t0 has elapsed after the start of charging during the transition period. Thereafter, the electric charge stored in the floating capacitance 72 is discharged again, and the charging of the floating capacitance 72 with the DC constant current I0 is started with the polarity reversed, and a predetermined time t0 after the start of charging in the transition period elapses. Voltage V2 across the stray capacitance 72
Is measured. Therefore, the voltage values V1 and V2 can be compared. At this time, if the soldering of all the pins 60 connected to both the patterns 68 and 70 is performed well, the value of the stray capacitance 72 can be reduced even if the direction of flowing the constant current I0 is reversed.
Become equal, and the voltage values V1 and V2 become V1 = V2 = (I
0 t0) / C. However, those pins 60
In a case where the soldering is partly or entirely defective and the foot is in a floating state, if the direction of flowing the constant current I0 is changed, the value C of the floating capacitance 72 becomes different, and the voltage values V1 and V2 are different. As a result, it is possible to determine the presence or absence of foot lifting only by inspecting the IC 56 mounted and soldered on the same substrate to be inspected.

[0113]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a flat package IC 1 mounted and soldered on a substrate to be subjected to a method for detecting a bridge and a bridge solder by an in-circuit tester of the IC according to the present invention.
FIG. 4 is a diagram illustrating a stray capacitance existing between an independent pattern connected to a pin and a ground of a substrate. In the figure, 30 is a flat package IC, 32 is a main body of the IC 30, 34, 3
Reference numerals 6, 38, and 40 denote input pins, output pins, power pins, ground pins, which protrude from the positive and rear sides of the main body 32, respectively.
42 is an independent pattern connected to the input pin 34, 44 is a ground of the substrate (not shown), and 46 is a floating capacitance existing between the independent pattern 42 and the ground 44 of the substrate. A plurality of input pins and output pins protrude from the main body 32, respectively.

FIG. 2 is a diagram showing an example of a measuring circuit by DC constant current charging for a stray capacitance in the case where the floating of a flat package IC on such a mounting board is inspected using an XY type in-circuit tester. In the figure, 48
Is a DC constant current power supply, 50 is an open / close switch, 52 is a voltmeter, and 54 (54a, 54b, 54c) is the ground of the measurement circuit. At the time of the inspection, first, two sets of XY units provided in the in-circuit tester are controlled, and one probe is connected to the input pin 34 by the independent pattern 42.
And the other probe is connected to the ground 4 of the board.
4 or a measurement point of an independent pattern (not shown) connected to the ground 44. Then, the open / close switch 50 connected to both probes is closed, and the electric charge stored in the floating capacitance 46 is discharged. Thereafter, the open / close switch 50 is opened, and charging by the DC constant current I0 is started from the power supply 48 via both probes.

Then, as shown in FIG. 3, during the transient period after the start of charging, the voltage V across the floating capacitance 46 increases proportionally with the passage of time t for a while. Therefore, the voltages V1 and V2 across the floating capacitance 46 when two different predetermined times t1 and t2 have elapsed after the start of charging during the transition are measured by the voltmeter 52, respectively. However, t1 <t2. Then, the value C of the stray capacitance 46 becomes C = ｛I0 × (t
2−t1)｝ / (V2−V1). For example, when t1 is 1 μs, t2 is 2 μs, and I0 is 200 mA, V1 and V2 are several mV to several tens mV, and C is several tens PF. It should be noted that these controls, calculations, etc.
U (central processing unit) or the like.

Therefore, if the value C0 of the stray capacitance of the same part of the same IC in which the other board is well soldered is calculated in advance, the value C of the stray capacitance 46 is calculated as follows. It can be compared with C0. At this time, if the soldering of the input pin 34 is defective and the foot is in a floating state, the stray capacitance 4
The value C of 6 is reduced by 20 to 30% from C0. Even if the input pin 34 is satisfactorily soldered to the independent pattern 42, the value C of the stray capacitance 46 is 2-3 times larger than C0 in the case of the bridge solder connected to the adjacent input pin 56 and the like by soldering. Increase by a percentage. As a result, regarding the input pin 34,
This makes it possible to determine whether the foot floats and whether there is a bridge solder.
The same applies to other input pins.

In the above-described embodiment, as an example, a method of detecting a foot floating and a bridge solder by DC constant current charging will be described with respect to a stray capacitance 46 existing between an independent pattern 42 connecting an input pin 34 and a ground 44 of a substrate. However, with respect to the stray capacitance (not shown) existing between the independent pattern connecting the output pin 36, the power supply pin 38, and the like and the ground 44 of the substrate, it is possible to similarly detect the floating foot and the bridge solder. . However, a floating foot or a bridge solder cannot be naturally detected between the independent pattern connecting the ground pins 40 and the ground 44 of the board.

Thus, the input pin 34 of the IC 30
And the value C of the stray capacitance 46 or the like existing between the independent pattern 42 or the like connecting the output pin 36 or the power supply pin 38 and the ground 44 of the substrate, and the value C of the stray capacitance 46 or the like When the presence / absence of the bridge solder is determined, a normal probe used for electrical measurement of other mounted components can be used as it is for the inspection of the foot lifting of the IC 30 and the bridge solder. Therefore, there is no need to manufacture an IC-dedicated probe and there is no need to replace the probe, so that the inspection can be speeded up.

FIG. 4 shows an independent pattern connected to one pin of a flat package IC soldered and mounted on a substrate to be subjected to a method for detecting a foot lift by an in-circuit tester for an IC according to the present invention, and another pin connected to another pattern. FIG. 9 is a diagram illustrating a stray capacitance existing between an independent pattern. In the figure, 56
Is a flat package IC, 58 is a main body of the IC 56, 6
0 (60a, 60b), 62, 64, and 66 are input pins and output pins that protrude from the positive and rear sides of the main body 58, respectively.
A power supply pin, a ground pin, and 68 are independent patterns connected to the input pin 60a, 70 is an independent pattern connected to the input pin 60b, and 72 is a floating capacitance existing between the patterns 68 and 70. Note that a plurality of input pins and output pins protrude from the main body 58, respectively.

FIG. 5 is a diagram showing an example of a measurement circuit by DC constant voltage charging of the stray capacitance when inspecting the floating of the IC on such a mounting board using an XY type in-circuit tester. In the figure, 74 is a DC constant voltage power supply,
76 (76a, 76b) is a changeover switch, 78 is an open / close switch, 80 is an ammeter, and 82 is the ground of the measurement circuit. At the time of inspection, first, two sets of XY units provided in the in-circuit tester are respectively controlled, one probe is brought into contact with the measurement point of the independent pattern 68 connecting the input pin 60a, and the other probe is input. It comes into contact with the measurement point of the independent pattern 70 connecting the pin 60b. And
The open / close switch 78 connected to both probes is closed, and the electric charge stored in the floating capacitance 72 is discharged. After that, the open / close switch 78 is opened, and each switch 7
6, one movable contact piece is closed on the upper side and the other movable contact piece is closed on the lower side, and a constant DC voltage V0 is applied from the power supply 74 via both probes to start charging the floating capacitance 72.

Then, during a transient period after the start of charging, the current I flowing through the floating capacitance 72 decreases in inverse proportion to the passage of time t for a while. Therefore, the current I1 when a predetermined time t0 has elapsed after the start of charging in the transient period is measured by the ammeter 80 connected in series to the constant voltage application circuit. Thereafter, the electric charge stored in the floating capacitance 72 is discharged again, and in order to reverse the polarity, the movable contacts of the respective changeover switches 76 are closed in opposite directions, and charging with the same DC constant voltage V0 is started. I do. Then, the current I2 when the same predetermined time t0 has elapsed after the start of charging in the transition period is measured. Therefore, the current values I1 and I2 can be compared. At this time, if the input pins 60 connected to both the patterns 68 and 70 are well soldered, the value C of the floating capacitance 72 can be obtained even if the direction of application of the constant voltage V0 to the floating capacitance 72 is reversed. Are equal, and the current values I1 and I2 are equal to I1 = I2 = (CV0) / t0. However, if the soldering of some or all of these input pins 60 is poor and the feet are floating, changing the application direction of the constant voltage V0 will cause the stray capacitance C to differ, and the current values I1 and I2 Are different. As a result, it is possible to determine the presence or absence of foot lifting. Incidentally, when the current value I2 is measured, the connection of the ammeter 80 is naturally reversed.

In the above embodiment, as an example, a DC constant voltage charge is applied to the stray capacitance 72 existing between the independent pattern 68 connecting one input pin 60a and the independent pattern 70 connecting the other input pin 60b. The method of detecting foot floating has been described above, but foot floating can be similarly detected by focusing on the stray capacitance existing between two independent patterns regardless of the number or type of pins connected to each independent pattern.

Thus, the input pin 6 of the IC 23
0, the output pin 62, the power supply pin 64, the ground pin 66, etc., and the two independent patterns 68, 70, etc., are charged with the stray capacitance 72, etc., existing between them. Currents I1 and I2 when the same predetermined time t0 elapses after the start of charging in both transition periods, respectively, and the two current values I1 and I2 are measured.
If the presence or absence of a foot lift is determined by comparing the two, the normal probe used for electrical measurement of other mounted components can be used as it is for the inspection of the IC 56 for the foot lift. In addition, since the presence or absence of foot lifting can be determined only by the IC 56, it is not necessary to compare it with another substrate. Therefore, there is no need to manufacture a probe dedicated to the IC or replace the probe, and it is not necessary to consider the variation in the stray capacitance due to the difference in the substrate to be inspected, so that the inspection can be speeded up.

FIG. 6 is a diagram showing an example of a measuring circuit by DC constant current charging for the stray capacitance in the case where the floating of the foot of the IC shown in FIG. 4 is inspected using an XY type in-circuit tester. In the figure, 84 is a DC constant current power supply, 86 (86a, 8
6b) is a changeover switch, 88 is an open / close switch, 90
Is a voltmeter, and 92 is the ground of the measurement circuit. At the time of inspection, as in the above embodiment, first, one probe is brought into contact with the independent pattern 68 connecting the input pin 60a, and the other probe is connected to the independent pattern 7 connecting the input pin 60b.
Contact 0. Then, after discharging the electric charge stored in the floating capacitance 72, a DC constant current I0 is supplied from the power source 84 to the floating capacitance 72 via both probes to start charging.
Then, naturally, the voltage V across the floating capacitance 72 increases proportionally with the lapse of time t for a while during the transient period after the start of charging. Therefore, the voltage I when the predetermined time t0 has elapsed after the start of charging within the transient time is measured by the voltmeter 90.
Measure 1.

After discharging the electric charge stored in the floating capacitance 72 again, the same constant current I0 is applied to the floating capacitance 72 with the polarity reversed, and charging is started. Then, the voltage V2 is measured when the same predetermined time t0 has elapsed after the start of charging in the transition period. Therefore, the voltage values V1 and V2
Can be compared. At that time, both patterns 68, 70
In the case where the input pins 60 connected to each other are well soldered, the value C of the stray capacitance 72 is equal even if the direction of flowing the constant current I0 is reversed, and the voltage values V1 and V2 are equal to V1.
= V2 = (I0 t0) / C. However, when the soldering of some or all of these input pins 60 is defective and the feet are floating, the stray capacitance C becomes different when the direction of flowing the constant current I0 is changed, and the voltage values V1 and V2 are changed. Are different. As a result, it is possible to determine the presence or absence of foot lifting. By the way, when measuring the voltage value V2, the connection of the voltmeter 90 is naturally reversed.

In the above embodiment, as an example, the DC constant current charging is performed with respect to the stray capacitance 72 existing between the independent pattern 68 connecting the one input pin 60a and the independent pattern 70 connecting the other one input pin 60b. The method of detecting a foot lift was described above, but it is also possible to detect a foot lift in the same manner by paying attention to the stray capacitance existing between two independent patterns regardless of the number or type of pins connected to each independent pattern. it can.

Thus, the input pin 6 of the IC 23
0, the output pin 62, the power supply pin 64, the ground pin 66, etc., and the two independent patterns 68, 70, etc., are charged with the stray capacitance 72, etc., existing between them. And the voltage values V1 and V2 are measured when the same predetermined time t0 has elapsed after the start of charging in both transition periods, and the two voltage values V1 and V2 are measured.
When the presence or absence of foot lifting is determined by comparing
A normal probe, which is also used for electrical measurement of other mounted components, can be used as it is for the inspection of the foot lift of the IC 56. In addition, since the presence or absence of foot lifting can be determined only by the IC 56, it is not necessary to compare it with another substrate. Therefore, there is no need to manufacture a probe dedicated to the IC or replace the probe, and it is not necessary to consider the variation in the stray capacitance due to the difference in the substrate to be inspected, so that the inspection can be speeded up.

[0028]

According to the present invention described above, according to the first and second aspects of the present invention, when inspecting the foot lift of an IC mounted and soldered on a substrate, an independent pattern for connecting at least one pin of the IC is used. Utilizing a stray capacitance existing between the other independent pattern connecting at least one pin and measuring a current value or a voltage value at both ends of the stray capacitance by DC constant voltage charging or DC constant current charging with respect to the stray capacitance. As a result, a normal probe used for electrical measurement of another mounted component can be used as it is for the inspection of the foot lift of the IC. In addition, since the presence or absence of foot lifting can be determined only by the IC, it is not necessary to compare with other substrates. Therefore, there is no need to manufacture a probe dedicated to the IC or replace the probe, and it is not necessary to consider the variation in the stray capacitance due to the difference in the substrate to be inspected, so that the inspection can be speeded up.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the presence of a foot lift by an in-circuit tester of an IC according to the present invention, between an independent pattern connected to pin 1 of a flat package IC soldered to a substrate to be subjected to a bridge solder detection method and ground of the substrate; FIG. 4 is a diagram showing a floating capacitance that changes.

FIG. 2 is a diagram showing an example of a measurement circuit by DC constant current charging with respect to a stray capacitance in the case of inspecting a floating foot of the flat package IC using an XY in-circuit tester.

FIG. 3 is a diagram showing a state in which the voltage across the stray capacitance increases proportionally with the passage of time for a while during a transient period after the start of charging.

FIG. 4 shows an independent pattern connected to one pin and an independent pattern connected to another one pin of a flat package IC soldered and mounted on a substrate to be subjected to a method for detecting a foot lift by an IC in-circuit tester according to another invention. FIG. 4 is a diagram showing a stray capacitance existing between the two.

FIG. 5 is a diagram showing an example of a measurement circuit by DC constant-voltage charging with respect to a stray capacitance in the case of inspecting a floating foot of the flat package IC using an XY system in-circuit tester.

FIG. 6 is a diagram showing an example of a measurement circuit using DC constant current charging for a stray capacitance in the case of inspecting a floating foot of the flat package IC using an XY system in-circuit tester.

FIG. 7 is a diagram showing an example of a measurement circuit in the case of inspecting a floating foot of a flat package IC soldered to a conventional mounting board by using an XY in-circuit tester.

[Explanation of symbols]

30, 56 ... Flat package IC 34, 56, 6
0 ... input pins 36, 62 ... output pins 38, 64 ... power supply pins 46, 66 ... ground pins 42, 68, 70
... Independent pattern 44 ... Ground of the board 46,72 ...
Stray capacitance 48, 84 DC constant current power supply 50, 78,
88 ... open / close switch 52, 90 ... voltmeter 54, 8
2, 92: ground of measurement circuit 74: DC constant voltage power supply 76, 86: changeover switch 80: ammeter

Claims (2)

(57) [Claims] In a method for detecting a foot lift of an IC mounted and soldered on a substrate by an in-circuit tester, the method includes the steps of:
After discharging the charge stored in the floating capacitance existing between the independent pattern connecting at least one pin and the independent pattern connecting the other at least one pin, the DC constant voltage charging of the floating capacitance is performed. After measuring the current at a lapse of a predetermined time after the start of charging in the transition period, discharging the charge stored in the stray capacitance again, and then charging the DC at the same constant voltage to the stray capacitance in the opposite direction. And starting, measuring the current after the same predetermined time has elapsed after the start of charging in the transition period, and determining the presence or absence of foot lifting by comparing the current value with the previously measured current value. Method of detecting foot lifting by an in-circuit tester of an IC. 2. A method for detecting foot lifting by an in-circuit tester of an IC mounted and soldered on a substrate, comprising the steps of:
After discharging the charge stored in the floating capacitance existing between the independent pattern connecting at least one pin and the independent pattern connecting the other at least one pin, a DC constant current charging for the floating capacitance is performed. After measuring the voltage at the elapse of a predetermined time after the start of charging in the transition period, discharging the charge stored in the stray capacitance again, and then charging the DC with the same constant current to the stray capacitance in the opposite direction. Starting, measuring the voltage at the same predetermined time after the start of charging in the transition period, and comparing the voltage value with the previously measured voltage value to determine the presence or absence of foot lifting. Method of detecting foot lifting by an in-circuit tester of an IC.