JPH0658989A - Short circuit detecting/testing method for wiring board - Google Patents

Abstract

PURPOSE:To facilitate short circuit test for wiring board. CONSTITUTION:In the method for detecting short circuit of wiring on a hybrid wiring board mounting receiving end matching termination LSIs 1 and sensing end matching termination LSIs 2, termination resistor 4 for the receiving end matching termination LSI 1 is provided with a probing pad 5. A predetermined voltage VTEST is applied on the probing pad 5 and a current, flowing at that time, is measured and then short circuit is detected based on the value of current thus detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short circuit detection test method for wiring boards. 2. Description of the Related Art In recent years, in mounting boards for information processing devices such as computers, there is an increasing demand for improvement in wiring density and via hole density of the boards as the number of pins of LSIs increases and the density of pins increases.

[0002] In order to meet such needs, for example, a thin film circuit substrate is formed on a ceramic substrate through a polyimide insulating layer via a polyimide insulating layer to realize high density wiring and via hole density. is doing.

However, since the wiring resistance per unit length becomes large due to the miniaturization of wiring, the transmission method of the matching termination method used at the receiving end of the wiring, which has been conventionally used, should be adopted due to the extreme decrease of the output level. I can't.

Therefore, there is a case where a transmission end matching termination type transmission system in which the transmission end is matched and the receiving end is opened. This sending end matching termination type LSI and the conventional receiving end matching termination type are used. There is a demand for a test method for efficiently performing a short-circuit detection test on the wiring board 3 on which the above LSIs are mixedly mounted.

[0005]

2. Description of the Related Art An ECL receiving end matching termination type output circuit is shown in FIG.
FIG. 4B shows an ECL transmission end matching type output circuit in FIG.
FIG. 5 shows a wiring board 3 on which the sending end matching termination type LSI 2 and the receiving end matching termination type LSI 1 are mixedly mounted.

In the receiving end matching termination type output circuit, an emitter follower circuit TREF and a terminating resistor 4 are connected to the outputs of the collectors of a plurality of transistors TR1, TR2 ,. Connected to the wiring pattern 12.

On the other hand, in the sending end matching type output circuit, a collector is added to the emitter of the emitter follower transistor TREF, and an emitter follower transistor TREF2 whose base is connected to a built-in reference voltage generating circuit (not shown) is added. It is connected to the wiring pattern 12 via the built-in terminating resistor 4.

To confirm the presence or absence of a short circuit in the wiring board 3 on which the receiving end matching termination type LSI and the sending end matching termination type LSI are mixedly mounted, first, the output logic levels of the two LSIs are made different from each other. In this case, for example, it is possible to probe the output pin 6 of the transmission end matching termination type and perform the operation according to the logic level.

The example shown in FIG. 5 is a sending end matching termination type LSI.
Output logic level to "L", receiving end matching termination type LSI
In this state, if the output of the sending end matching termination type LSI is "L", it means that there is no wiring short circuit.
If it is "H", then a wiring short circuit can be confirmed.

[0010]

However, in the above-mentioned conventional example, in order to detect a short circuit, it is necessary to set the LSIs to be measured to different output logic levels from each other, which requires a huge number of man-hours for the test. It had a drawback that

The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to provide a short-circuit detection test method for a wiring board which can easily perform a short-circuit detection test.

[0012]

According to the present invention, the above object is to mount a receiving end matching termination type LSI 1 and a sending end matching termination type LSI 2 in a mixed manner as shown in FIG. 1 corresponding to the embodiment. A short-circuit detection test method for a wiring board, which detects a wiring short-circuit of the wiring board 3, comprising a receiving end matching termination type LSI 1
A short circuit detection test method for a wiring board in which a probing pad 5 is provided on the terminating resistor 4, a predetermined voltage VTEST is applied from the probing pad 5, the current flowing at this time is measured, and the presence or absence of a short circuit is detected by the current value. Is achieved by providing.

Further, as shown in FIG. 2, in the sending end matching termination type LSI 2, the reference potential VREF higher than the "H" level potential and the potential of the output pin 6 are compared, and the comparison result is output outside the LSI 2. Incorporating a comparator 7 that outputs
A short circuit detection test method for a wiring board in which a voltage VTEST slightly higher than the reference potential VREF is applied to the probing pad 5 to record an output from the comparator 7 and a short circuit portion is identified based on the output from the comparator 7. Can also be configured.

Further, as shown in FIG. 3, the receiving end matching termination type LSI 1 is provided with a changeover switch 8 for switching between an operation mode and a test mode, and a current detection circuit 9 for detecting a current flow in the test mode. Can be provided, and a short-circuit detection test method for a wiring board that detects a short circuit between wirings depending on the presence / absence of an output from the current detection circuit 9 can be configured. In this case, the current detection circuit 9 includes each output pin 6 , 6, ..., And the decoder 1 outputs the output from the current detection circuit 9 corresponding to each output pin 6.
It is also possible to specify the short pin from the output of the decoder 10 by outputting through 0, and the current detection circuit 9 is turned on / off by the mode selection signal SM, the emitter is connected to the output terminal, and the collector is connected. It is also possible to include a switching transistor TRS having a collector resistance connected to the comparator, and a comparator 11 for comparing the collector output of the switching transistor TRS with the reference potential VREF.

[0015]

In the present invention, the terminating resistor 4 of the receiving end matching termination type LSI 1 is provided with the probing pad 5, and the short circuit is detected by the predetermined voltage VTE.
It is performed by applying ST. By applying the inspection voltage VTEST to the probing pad 5, a current flows to the sending end matching termination type LSI 2 side when the wiring has a short circuit portion, and no current flows when there is no short circuit.

Therefore, the circuit short circuit is detected only by applying the inspection voltage VTEST to the probing pad 5 and inspecting whether or not a current flows.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the present invention. In the figure, 2 is a sending end matching termination type LSI,
Reference numeral 1 is a receiving end matching termination type LSI, and 12 is a wiring pattern in the wiring board 3. Only the output stage is shown in the LSIs 1 and 2, and the specific configuration is the same as that shown in FIG.

The wiring pattern 12 connected to the receiving end matching termination type LSI 1 is connected to a terminating resistor 4 for impedance matching, and a probing pad 5 is formed in the vicinity of the terminating resistor 4. Further, in the short-circuit detection test, the terminating resistor 4 is brought into an open state.

In this state, in order to detect the short circuit between the LSIs 1 and 2, first, the voltage V slightly exceeding VOH is applied to the probing pad 5 from the external power source 13.
Apply TEST and measure the current value at that time.

At this time, no current flows unless the wiring patterns 12 are short-circuited. In the case of a short circuit, since the output pin 6 of the sending end matching termination type LSI is driven by the constant current source 14, FIG.
As indicated by the arrow in FIG. 5, a maximum IST current flows, and the presence or absence of a show is inspected by observing this current value.

FIG. 2 shows a second embodiment of the present invention. In this embodiment, the sending end matching termination type LSI 2 includes a comparator 7. A potential slightly higher than the output level of the "H" level of the LSI is applied to the inverting input terminal of the comparator 7 as the reference potential VREF, and the non-inverting input terminal is the output pin 6 of the LSI and the built-in terminating resistor 4 Connected between and. Further, the output of the comparator 7 is LS
It is output to the observation pin 14 provided on I2.

Under this structure, the wiring patterns 12, 12
The short circuit between them is observed by the following procedure. That is, first, from the external power source 13 to the probing pad 5,
A potential slightly higher than the reference potential VREF is applied. In this state, if there is no short circuit between the wiring patterns 12, the reference potential VREF of the comparator 7 is slightly higher than this even if the output of the sending end matching termination type LSI is at "H" level. The output of the comparator 7 is
It remains in the inverted state.

On the other hand, when there is a short circuit between the wiring patterns 12, the output potential of the external power source 13 is applied to the non-inverting input terminal of the comparator 7, which potential is higher than the reference potential VREF. Therefore, the output of the comparator 7 is inverted in the non-inversion direction.

Comparator 7 from each of these output pins 6
The output of is stored in a storage device (not shown), and after the inspection voltage VTEST is applied to all probing pads 5, the contents of the storage device are confirmed and the output pin 6 corresponding to the bit in which the output of the comparator 7 is inverted is set. By specifying, the short-circuited part is specified.

FIG. 3 shows a third embodiment of the present invention. In this embodiment, the receiving end matching termination type LSI 1 includes a short current detection circuit 9 and a decoder 10. The short-circuit current detection circuit 9 includes a switching transistor T inserted between the power supply line LV and the output pin 6.
It comprises RS (changeover switch 8) and a comparator 11 for comparing the collector potential of the switching transistor TRS with the reference potential VREF. The base of the switching transistor TRS has a mode selection for switching between the normal operation mode and the inspection mode. The signal SM is input.

That is, the receiving end matching termination type LSI 1 has the switching transistor TR in the normal operation mode.
The switching transistor TRS is connected to the base of S by "O".
The mode selection signal SM of the potential to be FF is input, the emitter output potential of the output transistor TREF is output to the output terminal, and in the inspection mode, the switching transistor TRS is turned “ON” by the mode selection signal SM and the collector potential. Is output to the comparator 11.

On the other hand, the reference potential VREF of the comparator 11
Is a value slightly higher than the voltage drop value due to the collector resistance of the switching transistor TRS. A plurality of short-circuit current detection circuits 9 are provided corresponding to each output pin 6 of the receiving end matching termination type LSI 1, and the output of the comparator 11 of each short-circuit current detection circuit 9 is supplied to the decoder 10. It

Therefore, in this embodiment, first, when the receiving end matching termination type LSI 1 is operated with the mode switched to the inspection mode, the collector potential of the switching transistor TRS becomes equal to the power supply level when the wiring pattern 12 is not short-circuited. As a result, the comparator 11 outputs "1" to the decoder 10. On the other hand, in the portion of the wiring pattern 12 where there is a short circuit, the short circuit current flows through the switching transistor TRS, so the collector potential becomes lower than the reference potential VREF, and the comparator 11 to the decoder 10 receive "0".
"Is output.

After the above, by observing the output of the decoder 10, the wiring pattern 12 to which the pin outputting "0" is connected in the bit string can be specified as the short circuit portion.

[0030]

As is apparent from the above description, according to the present invention, a short-circuit test is performed on a circuit board on which a sending end matching termination type LSI and a receiving end matching termination type LSI are mounted in a mixed manner. It can be done easily.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a third embodiment of the present invention.

4A and 4B are diagrams showing a matching termination type, wherein FIG. 4A shows an output circuit of a receiving end matching termination type LSI, and FIG. 4B shows an output circuit of a sending end matching termination type LSI.

FIG. 5 is a diagram showing a conventional example.

[Explanation of symbols]

 1 Receiving end matching termination type LSI 2 Sending end matching termination type LSI 3 Wiring board 4 Termination resistor 5 Probing pad 6 Output pin 7 Comparator 8 Changeover switch 9 Current detection circuit 10 Decoder 11 Comparator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/66 E 8406-4M 23/12 301 Z 9355-4M

Claims (5)

[Claims] 1. A wiring board short circuit detection test method for detecting a wiring short circuit of a wiring board (3) on which a receiving end matching termination type LSI (1) and a sending end matching termination type LSI (2) are mixedly mounted. Therefore, a probing pad (5) is provided on the terminating resistor (4) of the receiving end matching termination type LSI (1), a predetermined voltage (VTEST) is applied from the probing pad (5), and the current flowing at this time is changed. A short circuit detection test method for a wiring board, which measures and detects the presence or absence of a short circuit based on the current value. 2. The sending end matching termination type LSI (2) comprises:
A comparator (7) for comparing the reference potential (VREF) higher than the H ″ level potential with the potential of the output pin (6) and outputting the comparison result to the outside of the LSI (2) is incorporated, and the probing pad (5) ) Is applied with a voltage (VTEST) that is slightly higher than the reference potential (VREF),
A short circuit detection test method for a wiring board, wherein the output from (7) is recorded and the short circuit location is identified based on the output from the comparator (7). 3. The receiving end matching termination type LSI (1) includes a changeover switch (8) for switching between an operation mode and a test mode, and a current detection circuit (9) for detecting a current flow in the test mode. ) Is provided, and a short circuit detection test method for a wiring board is provided, which detects a short circuit between wirings by the presence or absence of an output from the current detection circuit (9). 4. The current detection circuit (9) has output pins
(6, 6 ...) A plurality of current detection circuits (9) are provided corresponding to each output pin (6) and output through the decoder (10), and the decoder (10) 4. The short circuit detection test method for a wiring board according to claim 3, wherein the short pin is specified from the output of FIG. 5. A mode selection signal for the current detection circuit (9).
(SM) turns ON / OFF, the emitter is connected to the output terminal, the collector is connected to the collector transistor (TRS), the collector output of the switching transistor (TRS) and the reference potential (VREF) The short circuit detection test method for a wiring board according to claim 4 or 5, further comprising a comparator (11) for comparing