JPH07218580A - Digital ic leg floatage, bridge solder detecting method by in-circuit tester - Google Patents

Abstract

PURPOSE:To make no need of a probe exclusively used for a digital IC and carry out inspection at high speed. CONSTITUTION:Regarding digital ICs 30, 32 which are mounted on and soldered with a board and are provided with a plurality of input protective circuits connecting all the electric power source pins 34, 40 to one another and all the ground pins 38, 44 to one another in respectively independent patterns 46, 50 and connecting at least one input pin 42 with one output pin 36 in an independent pattern 48; a.c. or d.c. rated voltage is applied between the independent pattern 48, in which the input and output pins 42, 36 are connected, and either the independent pattern 46 or the independent pattern 50, in which all the electric power source pins 34, 40 or all the ground pins 38, 44 are connected respectively, and the electric current between the patterns 48 and either 46 or 50 is measured. Based on the obtained current value, whether leg floating and bridge soldering exist or not is judged.

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 foot floating and bridge soldering of a plurality of digital ICs with input protection mounted and soldered on a printed circuit board using an in-circuit tester.

[0002]

2. Description of the Related Art Conventionally, a printed circuit board, that is, a printed circuit board to which various electronic parts are soldered, uses an in-circuit tester, and a probe is appropriately contacted with each necessary measurement point on the board to electrically connect the parts. The quality of the substrate is determined by dynamic measurement. In particular, the one in which the XY unit is installed on the measuring table on which the board to be inspected is mounted has the Z-axis unit movable in the Y-axis direction on the arm movable in the X-axis direction. Since the probe is supported so as to be movable 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 to set each preset value. The measurement points can be contacted in sequence. Since it is necessary to simultaneously measure a plurality of measurement points for each component, an XY in-circuit tester is usually equipped with a plurality of sets of XY units.

When using such an in-circuit tester to inspect a contact failure with a pin pattern due to a soldering failure of a digital IC (integrated circuit) mounted and soldered on a printed circuit board, that is, a floating foot, FIG. A dedicated probe 16 in which the tip portion 10 as shown is expanded and the tip portion 10 is composed of a laminated body of a metal electrode 12 and an insulator 14 is used. At the time of inspection, the tip portion 1 of the dedicated probe 16
0 is widely contacted with the upper surface of the main body of the digital IC 18, and another normal probe 20 is contacted with the pattern 22 on the substrate.
A constant voltage is applied between the probes 16 and 20 from the AC constant voltage power source 26, the current is measured using the ammeter 28, and the presence or absence of foot floating is determined by the current value. At this time, since the dedicated probe 16 and the main body of the digital IC 18 form a capacitor of several PF, the current value becomes large if the soldering of the pin 24 and the pattern 22 is good, but the current becomes large if the foot is in a floating state. The value becomes smaller. The general probe 20 is elongated to the tip and has a spring property in the axial direction. The tip is applied to a measurement point and a static load is applied to obtain electrical contact.

[0004]

However, such a dedicated probe 16 is used only when inspecting the soldering state of the pin 24 and the pattern 22 of the digital IC 18 among various electronic components mounted and soldered on the printed circuit board. There is a problem because it is a dedicated tool used for. This is because the normal probe 2 is used when making electrical measurements of other electronic components.
This is because 0 is used, and the inspection probe becomes heavy if the dedicated probe 16 is required only for the inspection of the floating of the digital IC 18. In particular, in the XY type in-circuit tester, the dedicated probe 16 must be attached to one XY unit only when inspecting the floating of the digital IC 18, but with the normal probe 20 used up to that point. It takes time to replace the dedicated probe 16. Therefore, the inspection cannot be speeded up, which is inconvenient.

Incidentally, a plurality of digital I's are provided on the printed circuit board.
When C is mounted, normally all the power supply pins and all the ground pins of those digital ICs are connected in independent patterns, but at least one input pin and one output pin are further connected between the digital ICs. Many are connected through independent patterns. Moreover, each digital IC usually has an input protection circuit.

The present invention has been made by paying attention to such a conventional problem, and by utilizing a peculiar connection relation existing between digital ICs, the need for a dedicated probe for the digital ICs is eliminated. An object of the present invention is to provide a method for detecting foot floating and bridge solder by an in-circuit tester of a digital IC, which can speed up inspection.

[0007]

In order to achieve the above object, in the method for detecting foot floating and bridge soldering by an in-circuit tester of a digital IC according to the present invention, all the power supply pins 34 and 40 are mounted on a board and soldered. All ground pins 38 and 44 are connected by independent patterns 46 and 50, respectively, and at least one input pin 42 and one output pin 3 are connected.
The input / output pin 4 is connected to a plurality of digital ICs 30 and 32 with an input protection circuit for connecting 6 by an independent pattern 48.
Independent pattern 48 connecting 2 and 36, and all power pins 3
Between the independent pattern 46 connecting 4 and 40 or the independent pattern 50 connecting all the ground pins 38 and 44,
The current is measured by applying a constant voltage of AC or DC, and the presence or absence of foot floating and bridge soldering is determined by the current value.

[0008]

The internal equivalent circuit of the input pin of the digital IC 32 with the input protection circuit has two diodes 60 and 62 connected in series between the power supply pin 40 and the ground pin 44 with their cathodes facing the power supply pin 40 side. , A resistor 64 is connected between the input pin 42 and the connection point of the diodes 60 and 62, and the output pin internal equivalent circuit has two diodes 5 between the power supply pin 34 and the ground pin 38.
2, 54 are connected in series with each cathode facing the power supply pin 34 side, and the output pin 36 and the connection point of both diodes 52, 54 are directly connected. Therefore, the probe is brought into contact with the independent pattern 48 that connects the input / output pins 42 and 36, the independent pattern 46 that connects all the power supply pins 34 and 40, or the independent pattern 50 that connects all the ground pins 38 and 44. When a constant voltage of AC or DC is applied from the power source 66, the constant voltage is applied to the diode 60.
Alternatively, it is added to the series circuit of the resistor 62 and the resistor 64 and the diode 52 or 54 connected in parallel to both ends thereof.

Therefore, if an ammeter 68 is connected in series to the constant voltage application circuit, the current (combined current) flowing to the outside through these internal circuits can be measured. At that time, each of the independent patterns 46, 48 or 48, 50 with which both probes come into contact
To each pin 34, 36, 40, 42 or 36, 3
Currents when all of the soldering of Nos. 8, 42, 44 are performed well, and the respective pins 34, 36, 40, 42 of those currents
Alternatively, when compared with the current when one or more soldering of 36, 38, 42 and 44 is defective and the feet are in a floating state, the current value of the latter is reduced by 20 to 30%. However, in the case of bridge solder in which the input pins or output pins of the same digital IC are connected by solder, the current value increases by 20 to 30%. As a result, it is possible to determine whether or not the foot is floating and the bridge solder is present based on the current value. If multiple output pins are connected to one input pin in an independent pattern, multiple diodes are connected in parallel in a series circuit of a diode and a resistor. If a plurality of input pins are connected in an independent pattern, a plurality of series circuits of a diode and a resistor are connected in parallel to the diode.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows two digital I with an input protection circuit mounted and soldered on a substrate which is a target of a method for detecting a floating foot by an in-circuit tester of a digital IC according to the present invention.
It is a figure which shows the peculiar connection relation which exists between C. In the figure,
30 and 32 are first and second digital ICs, 34, 36 and 3
Reference numeral 8 denotes power supply, output, and ground pins of the first digital IC 30, 40, 42, and 44 denote power supply, input, and ground pins of the second digital IC 32, and 46 denotes both power supply pins 34,
Independent pattern connecting 40, 48 input / output pin 36,
Independent pattern for connecting 42, 50 for both ground pins 3
It is an independent pattern that connects 8 and 44. The independent pattern 46 is connected to the power source, and the independent pattern 50 is connected to the ground of the substrate (not shown).

The output pin internal equivalent circuit of the first digital IC 30 has two diodes 52 and 54 between the power supply pin 34 and the ground pin 38 as shown in FIG. Connected in series and output pin 3
6 and the connection point of both diodes 52 and 54 are directly connected. The FETs 56 and 58 are regarded as equivalent to the diodes 52 and 54, respectively. Further, the input pin internal equivalent circuit of the second digital IC 32 is provided with an input protection circuit so that two diodes 60 and 62 are provided between the power supply pin 40 and the ground pin 44 as shown in FIG. It has a configuration in which it is connected in series toward the pin 40 side, and a resistor 64 is connected between the input pin 42 and the connection point of the diodes 60 and 62.

FIG. 4 is a diagram showing a circuit example in the case of inspecting the floating of the digital IC on such a mounting board by using an XY type in-circuit tester. 66 in the figure
Is an AC or DC constant voltage power source, 68 is an ammeter, 70 (7
0a, 70b) is the ground of the measurement circuit. At the time of inspection, first, two sets of XY provided for the in-circuit tester.
Each unit is controlled, and one probe is brought into contact with the independent pattern 48 connecting the input / output pins 42 and 36, and the other probe is brought into contact with the independent pattern 46 connecting the power supply pins 34 and 40. Therefore, when a constant voltage is applied from the power source 66, the constant voltage is applied to the series circuit of the diode 60 and the resistor 64 and the diode 52 connected in parallel to both ends thereof. Therefore, if an ammeter 68 is connected in series to the constant voltage application circuit, the current (combined current) flowing to the outside through these internal circuits can be measured. Therefore, the currents when the pins 34, 36, 40, 42 are soldered well to the independent patterns 46, 48 with which the probes contact each other, and the respective pins 34, 36, 4 of those pins.
Comparison is made with the current when one or more soldering of Nos. 0 and 42 are defective and the feet are in a floating state. Then, in the latter case, the current value is reduced by 20 to 30%, so that it is possible to determine whether or not the foot is floating based on the current value.

As shown in FIG. 5, one probe is brought into contact with the independent pattern 50 connecting the ground pins 38 and 44, and the other probe is brought into contact with the independent pattern 48 connecting the input / output pins 42 and 36. Similarly, a constant voltage may be applied from the power source 66. At that time, a constant voltage is applied to the series circuit of the diode 62 and the resistor 64 and the diode 54 connected in parallel at both ends thereof. Therefore, the current when the pins 36, 38, 42, and 44 are all well soldered to the independent patterns 48 and 50 with which the probes contact each other by the ammeter 68, and the pins 3 and the like.
Comparing with the current when one or more soldering of 6, 38, 42 and 44 is defective and the feet are in a floating state, the current value also decreases by 20 to 30% in the latter case. The presence or absence of floating feet can be determined by.

In this way, the digital ICs 30, 32 are
On the other hand, a constant voltage is provided between the independent pattern 48 connecting the input / output pins 42 and 36 and the independent pattern 46 connecting the power supply pins 34 and 40 or the independent pattern 50 connecting the ground pins 38 and 44. When a current is applied to measure the current and the presence / absence of a foot float is determined based on the current value, a normal probe used for electrical measurement of other mounted components can be used as it is for the foot float inspection of the digital ICs 30 and 32. . Therefore, it is not necessary to manufacture a probe for exclusive use of the digital IC, and there is no need to replace the probe, so the inspection can be speeded up. If multiple output pins are connected to one input pin in an independent pattern, multiple diodes will be connected in parallel to the series circuit of the diode and the resistor. If a plurality of input pins are connected in an independent pattern, a series circuit of a diode and a resistor is connected in parallel to the diode.

In the above embodiment, the detection of the floating foot of the digital IC has been described. However, the same detection method is adopted in the case of bridge solder in which adjacent input pins or output pins of the same digital IC are connected by solder. As compared with the normal case, the current value changes, so detection becomes possible. However, in the case of bridge soldering, the current value increases by 20 to 30% compared to the normal case.

[0016]

According to the present invention described above, the peculiar connection relationship existing between digital ICs is utilized even when inspecting the foot float and bridge solder of a plurality of digital ICs mounted and soldered on a substrate. As a result, a normal probe used for electrical measurement of other mounted components can be used as it is. Therefore, it is not necessary to manufacture a probe for exclusive use of the digital IC, and there is no need to replace the probe, so the inspection can be speeded up.

[Brief description of drawings]

FIG. 1 is a diagram showing a peculiar connection relationship existing between two digital ICs with an input protection circuit mounted and soldered to a substrate which is a target of a foot floating detection method by an in-circuit tester of a digital IC according to the present invention. .

FIG. 2 is a diagram showing an output pin internal equivalent circuit of the digital IC.

FIG. 3 is a diagram showing an input pin internal equivalent circuit of the digital IC.

[Fig. 4] It is possible to prevent the digital IC from floating on the same mounting board.
It is a figure which shows the example of a circuit at the time of inspecting using a -Y system in-circuit tester.

FIG. 5 shows the floating of digital ICs on the same mounting board as X.
It is a figure which shows the other circuit example at the time of inspecting using a -Y system in-circuit tester.

FIG. 6 is a diagram showing a circuit example in the case of inspecting a floating foot of a digital IC on a conventional mounting board using an XY type in-circuit tester.

[Explanation of symbols]

30, 32 ... Digital IC 34, 40 ... Power supply pin 3
6, 42 ... Out, input pin 38, 44 ... Ground pin
46, 48, 50 ... Independent patterns 52, 54, 60,
62 ... Diode 64 ... Resistor 66 ... Constant voltage power supply 6
8 ... Ammeter

Claims (1)

[Claims] 1. A digital circuit with a plurality of input protection circuits, which is mounted on a board and soldered, all power pins and all ground pins are connected in independent patterns, and at least one input pin and one output pin are connected in independent patterns. In a method for detecting foot floating and bridge soldering by an IC in-circuit tester, an independent pattern for connecting the input / output pins,
A characteristic is that a constant voltage of AC or DC is applied between an independent pattern connecting all power pins or all ground pins to measure the current, and the presence or absence of floating feet and bridge solder is determined by the current value. A method for detecting foot float and bridge solder by an in-circuit tester of a digital IC.