JP2763793B2 - Printed wiring board inspection equipment - Google Patents

Description

Detailed Description of the Invention [Table of Contents] Overview Industrial application field Conventional technology (FIGS. 15 and 16) Problems to be Solved by the Invention Means for Solving the Problems (FIG. 1) Action Embodiment configuration example (FIG. 2-FIG. 5) operation I. inspection procedure II. reflected wave S _B of the waveform (line quality determination method) of example (1) waveform (Figure 6 when there is no defect in the wiring , FIG. 7A
~ D) (2) Waveform when wiring is defective When there is a disconnection in the pattern part (Figs. 8 and 9) When there is a disconnection in the through-hole part (Figs. 10 and 11) When there is a defect (FIG. 12) When there is a stub (FIGS. 13 and 14) Effects of the embodiment Other effects of the invention [Overview] Printed wiring for inspecting the quality of wiring formed on a printed wiring board Regarding board inspection equipment, besides disconnection and short circuit, defective characteristic impedance,
Applicable to the inspection of printed wiring boards for ultra-high-speed electronic circuits by making it possible to detect the presence of stubs and faulty wiring lengths, and equipment that makes it possible to inspect printed wiring boards for surface mounting from one side The purpose of the multi-probe head is to avoid the increase in size, complexity, and cost of the probe, and to prevent damage to the printed wiring board by reducing the number of probes and reducing the pressure applied to the printed wiring board. A multi-probe head moving means, a multi-probe head movement controlling means, a wiring design data storing means, a measuring point indicating means, a step pulse applying / reflection waveform measuring means, and a wiring good / bad determining means; To apply a step pulse to the wiring
The configuration is such that the waveform of the reflected wave is measured and analyzed, and the result of the analysis is compared with the wiring design data so that the quality of the wiring can be inspected.

[Industrial Application Field] The present invention relates to a printed wiring board inspection apparatus for inspecting the quality of wiring formed on a printed wiring board.

Generally, printed wiring boards are incorporated into electronic devices,
Before being shipped, we undergo various inspections in each process.
This is because the cost of finding defective parts and repairing them increases as the process progresses, in other words, removes it at the process where the defect occurred, sends only non-defective products to the subsequent process, and The aim is to reduce costs and improve quality.

Here, for example, after forming the wiring and before mounting the components, an inspection of the wiring is performed using a printed wiring board inspection apparatus.

[Prior Art] Conventionally, there has been proposed a printed wiring board inspection apparatus whose schematic configuration is shown in FIG.

In the figure, reference numeral 1 denotes a jig in which a number of probes 3 are arranged on a pin board 2, a so-called nail bed; 4, a scanner relay; 5, a voltage supply device for outputting a predetermined voltage, for example, a DC voltage of 1 [V]; Reference numeral 6 denotes a voltage detection device, and reference numeral 7 denotes a table on which the printed wiring board 8 is placed.

In particular, the nail bed 1 has probes 3 arranged in a grid pattern on a pin board 2 as shown in the rear view in FIG. 16 so that these probes 3 correspond to all the basic grids of the printed wiring board 8. Is configured. In other words, the nail bed 1 is for contacting the probe 3 with all the measurement points on the printed wiring board 8, and for example, is for inspecting a printed wiring board 8 of 50 cm × 50 cm. Is about 200 × 2 on a pin board 2 of about 50cm × 50cm
00 probes 3 are provided. Further, these probes 3 are constituted by probes with springs.

Such a printed wiring board inspection apparatus presses the probe 3 against the through hole of the printed wiring board 8, sequentially applies a DC voltage to all the probes 3, and measures the voltages of the other probes 3. Is compared with pass / fail data to determine the presence / absence of disconnection and short circuit.

[Problems to be Solved by the Invention] The conventional printed wiring board inspection apparatus has the following problems.

(1) First, in a printed wiring board for an ultra-high-speed electronic circuit, in addition to disconnection and short-circuiting, defective characteristic impedance, the presence of a stub (an unnecessary line whose other end is not connected to anywhere), and other wiring There is a need to detect long defects.

However, in the conventional printed wiring board inspection apparatus, the quality of the wiring is inspected by applying a DC voltage to the wiring, so that a disconnection or a short circuit can be detected, but the characteristic impedance is poor and the presence of a stub is present. However, it is not possible to detect a defect in the wiring length, and therefore, there is a problem that the method cannot be applied to the wiring inspection of a printed wiring board for an ultra-high-speed electronic circuit.

(2) Next, in the conventional printed wiring board inspection apparatus, it is necessary to simultaneously probe at least two points of a voltage application point and a voltage measurement point. Therefore, when this apparatus is used to inspect the wiring of a surface-mounted printed wiring board having no through holes for mounting components, there are places where inspection cannot be performed from one side.

For this reason, when inspecting a printed wiring board for surface mounting, it must be configured so that probing can be performed from both the front and back surfaces of the printed wiring board, and the device becomes large, complicated, and expensive. There was a point.

(3) Further, in the conventional printed wiring board inspection apparatus, the pin board 2
The number of probes 3 to be planted in is huge,
Manufacture and maintenance of the nail bed 1 are extremely difficult, and very large pressure is required to press the probe 3 against the printed wiring board 8. For this reason, the device becomes large and the printed wiring board 8
However, there is a problem that the probe may be damaged by the pressure of the probe 3.

In view of such a point, the present invention, in addition to disconnection and short-circuit,
Application to inspection of printed wiring boards for ultra-high-speed electronic circuits by enabling detection of defective characteristic impedance, presence of stubs, and defective wiring length, and inspection from one side of printed wiring boards for surface mounting It is possible to avoid the increase in size, complexity, and cost of the apparatus by reducing the number of probes, and to prevent the damage to the printed wiring board by reducing the pressure applied to the printed wiring board. It is an object of the present invention to provide a printed wiring board inspection apparatus.

[Means for Solving the Problems] The printed wiring board inspection apparatus of the present invention has a multi-probe head 10 as shown in FIG.
Multi-probe head moving means 11, multi-probe head movement control means 12, wiring design data storage means 13,
And measurement point indicating means 14, step pulse application / reflection waveform measuring means 15, and wiring quality judgment means 16. 17 is a printed wiring board, 18 is a printed wiring board
This is the wiring formed at 17.

Here, the multi-probe head 10 is configured by arranging probes 19 on the pin board 9 in a square shape at regular intervals.

The multi-probe head moving means 11 moves the multi-probe head 10 in the vertical, horizontal, and height directions.

Further, the multi-probe head movement control means 12 controls the multi-probe head movement means 11 to move the multi-probe head 10 and to move the probe 19 to the printed wiring board 17.
The wiring 18 is brought into contact with the designated measurement point.

The wiring design data storage means 13 is a printed wiring board.
This is to store the design data of the wiring 18 formed in 17.

Further, the measurement point instructing means 14 instructs the multi-probe head movement control means 12 to specify a measurement point based on the design data of the wiring 18.

Also, the step pulse application / reflection waveform measuring means 15
Through the probe 19, the step pulse S _A is applied to the measurement point, which measures the waveform of the reflected wave S _B.

In addition, the wiring pass / fail determination means 16 applies a step pulse
The waveform of the reflected wave S _B which reflected waveform measuring means 15 to measure the analyzed against the result of the analysis on the design data of the wiring 18, is to determine the quality of the wiring 18.

In [Operation] The present invention, by applying a step pulse S _A to the measuring point via the probe 19, since it is adapted to measure the waveform of the reflected wave S _B, i.e., so-called TDR (Time Doma
In Reflectometry) method, not only disconnection and short circuit of the wiring 18, but also poor characteristic impedance,
The presence of the stub and the defect of the wiring length can be detected.

For the same reason, it is not necessary to probe at least two points of the voltage application point and the voltage measurement point at the same time as in the conventional example in FIG. 15, and it is sufficient to probe only one point. Therefore, even when inspecting a printed wiring board for surface mounting, it is not necessary to probe the front and back surfaces of the printed wiring board.

In the present invention, the multi-probe head 10
Is configured by arranging the probes 19 in a bracket shape and at regular intervals, and further comprises a multi-probe head moving means 1.
1.Provide a multi-probe head movement control means 12 and a measurement point indicating means 14, move the multi-probe head 10 so that the probe 19 contacts a bonding pad formed on the IC chip mounting portion, and perform local measurement. Since it is possible to perform the inspection of the wiring 18 with a small number of probes 19 without increasing the number of probes 19 corresponding to the high density of the printed wiring board 17 it can.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 2 to 14.

FIG. 2 and FIG. 3 are a block diagram and a schematic perspective view, respectively, showing an embodiment of the present invention.
It is provided with a probe device 20, a control computer 21, a coaxial multiplexer 22, and a TDR measuring device 23.

Here, the probe device 20 is a multi-probe head 2
4. A multi-probe head moving means 25 and a multi-probe head movement control means 26 are provided.

As shown in the back view of FIG. 4, the multi-probe head 24 has the probes 28 arranged in a square shape around the back surface of the pin board 27 at regular intervals, for example, at intervals of 2.54 mm. . This is, for example, as shown in FIG. 5, a plurality of IC chips having the same size and the same shape.
Printed wiring board with bonding pads 30 of the same pattern formed on each IC chip mounting part to mount 29
This is suitable for inspecting the wiring 32 of 31. That is, all the probes 28 come into contact with all the bonding pads of one bonding pad group 30.

Further, the multi-probe head moving means 25 is configured to move the multi-probe head 24 on the printed wiring board 31 in the vertical, horizontal, and height directions. In FIG. 3, reference numeral 33 denotes an arm constituting a part of the multi-probe head moving means 25.

The multi-probe head movement control means 26 is configured to control the multi-probe head movement means 25 to move the multi-probe head 24 and bring the probe 28 into contact with the designated measurement point.

Further, the control computer 21 includes a wiring design data storage unit 34,
The configuration is provided with measurement point indicating means 35 and wiring quality judgment means 36.

Here, the wiring design data storage means 34 stores the design data of the wiring 32, for example, the number and the coordinates of the IC chips 29, the number and the coordinates of the measuring points related to the individual wirings 32, the characteristic impedance, and the line between the measuring points. It is configured to be able to store the length, the connection order of the measurement points, and the like.

The measurement point indicating means 35 is a wiring forming data storage means.
Based on the design data of the wiring 32 stored in 34, the measuring point is instructed to the multi-probe head movement control means 26 of the probe device 20, and the coaxial multiplexer 22 and the TDR measuring device 23 are controlled to The TDR measurement is performed every time.

That is, under the control of the measurement point designating means 35, the coaxial multiplexer 22 sequentially selects one probe 28 from a large number of probes 28, and selects the selected probe 28 and the TDR measuring device 23.
And are configured to be connected. In addition, TDR measuring instrument 2
3 is also controlled by the measuring point indicating means 35, and in synchronization with the selecting operation of the coaxial multiplexer 22, the selected probe 28
Is configured to the step pulse S _A is applied, it can be measured waveform of the reflected wave S _B respect.

The wiring quality determination unit 36 of the control computer 21 takes a waveform of the reflected wave S _B which TDR meter 23 has measured, wiring analyzes this stored results of this analysis in the wiring design data storage means 34 32 The configuration is such that the quality of the wiring 32 can be determined based on the design data.

Per operations of the embodiment examples, I. Inspection procedure, II. Will be described separately terms to the reflected wave S _B of the waveform (line quality judgment process).

I. Inspection Procedure The inspection of the wiring 32 is performed by the following procedure.

(1) The measurement point indicating means 35 is a wiring design data storage means 34
A measurement point is instructed to the multi-probe head movement control means 26 of the probe device 20 on the basis of the design data of the wiring 32 stored in the probe device 20, and the probe 28 is brought into contact with the measurement point.

(2) The measuring point indicating means 35 controls the coaxial multiplexer 22 and the TDR measuring device 23 to perform the TDR measurement for each measuring point.

(3) Wiring quality determining unit 36, captures the waveform of the reflected wave S _B which TDR meter 23 has measured, analyzes the design data of the analysis results wiring design data storage unit 34 is stored in the wiring 32 Then, the quality of the wiring 32 is determined.

(4) Repeat the above operation.

II. Whether the reflected waveform (line quality determination method) of S _B is defective wiring 32 is determined by the waveform of the reflected wave S _B. Therefore, hereinafter, an example in which the wiring 32 has a pattern as shown in FIG.
When there is no defect in the wiring 32 and (2) when the wiring 32 has a defect, what kind of waveform is measured will be clarified.

In the drawing, a, b, c, and d are measurement points (through holes), respectively, and 37 is a measurement reference cable having a characteristic impedance of 50 [Ω].

(1) FIG. 7 A~D If there is a defect in the wiring 32 is a waveform of the reflected wave S _B obtained when defective lines 32 shown in Figure 6 does not exist. In addition,
7A to 7D, the vertical axis is the reflection coefficient ρ, and the horizontal axis is the time axis. Hereinafter, the same applies to the figures showing waveforms.

Seventh Figure A shows the waveform of the reflected wave S _B when contacting the probe 28 to a point. In the waveform, a step 38 indicates reflection at point a, and a step 39 indicates reflection at point d. That is, the α portion is due to the reflected wave of the measurement reference cable 37, and the β portion is due to the reflected wave from the point a to the point d. Since the reflection coefficient of the γ portion is “+1”, the impedance after point d indicates that the impedance is infinite.

Here, the characteristic impedance Z of the wiring 32 can be obtained by the following equation.

Here, Z ₀ is the characteristic impedance (reference impedance) of the measurement reference cable 37, and Δρ is the difference between the reflection coefficients of the α and β parts.

Further, since the propagation delay time per unit wiring length is determined by the dielectric constant of the insulating material of the printed wiring board, the wiring length can be obtained from the time Δt.

Figure 7 B shows the waveform of the reflected wave S _B when contacting the probe 28 to the point b. In the waveform, a step 40 indicates reflection at point b. That is, in this case, the step pulse
S _A is to proceed towards the two positions of a point and the point d, in the portion corresponding to point b, so that half the original impedance is observed. Then, in the case of this example, there are two end portions (points a and d).
Multiple reflection occurs, Therefore, the waveform of the reflected wave S _B is complicated as shown in FIG.

Figure 7 C shows a waveform of the reflected wave S _B when contacting the probe 28 to point c. In the waveform, the step 41 shows the reflection at the point c.
S _A is to proceed towards the two positions of a point and the point d, in the portion corresponding to point c, so that half the original impedance is observed. Then, further multiple reflection occurs, the waveform of the reflected wave S _B is complicated as shown in FIG.

Figure 7 D shows the waveform of the reflected wave S _B when contacting the probe 28 to the point d. In the waveform, a step 42 indicates reflection at point d, and a step 43 indicates reflection at point a.

(2) When there is a defect in the wiring When there is a defect in the wiring 32, the following describes the case where there is a break in the pattern portion, the case where there is a break in the through hole portion, the case where there is a defect in the characteristic impedance, and the case where there is a stub. , Will be described separately.

If there is a disconnection in the pattern portion for example, as shown in FIG. 8, when there is disconnection 44 between ab, when a measurement point a point, shown in FIG. 9 as the waveform of the reflected wave S _B Such a waveform can be measured. In the waveform, the step 45 is the reflection at the point a, the step
46 indicates the reflection at the disconnection portion 44. Also, the broken line 47
Shows a waveform when there is no disconnection 44 (see FIG. 7A).

If there is a disconnection in the through-hole portion for example, as shown in FIG. 10, in a case where the point b is disconnected 48, when the point b to the measuring point, in Figure 11 as the waveform of the reflected wave S _B The waveform as shown can be measured. In the waveform, a step 49 indicates reflection at point b. A broken line 50 shows a waveform when there is no disconnection 48 (see FIG. 7B).

In the case where when the wiring 32 to the characteristic impedance is defective is defective in characteristic impedance, in the case of the measurement points a point, to measure the waveform as shown in FIG. 12 as a waveform of the reflected wave S _B it can. In the waveform, a step 51 indicates reflection at point a, and a step 52 indicates reflection at point d. A broken line 53 shows a waveform in an emergency case (see FIG. 7A).

If there is a stub for example, as shown in FIG. 13, when there is a stub 55 to the point 54 between ab, when a measurement point a point, shown in FIG. 14 as a waveform of the reflected wave S _B Such a waveform can be measured. In the waveform, a step 56 indicates reflection at point a, a step 57 indicates reflection at point 54, and a step 58 indicates reflection at point d. The broken line 59 is a stub
A waveform when 55 does not exist is shown (see FIG. 7A).

Further, even when there is a short circuit with another net, a similar waveform can be measured.

Thus the effect of the embodiment according to the present embodiment, by applying a step pulse S _A to the measuring point via the probe 28, measures the waveform of the reflected wave S _B, since it is adapted to analyze It is possible to detect not only the disconnection and short-circuit of the wiring 32, but also the defect of the characteristic impedance, the presence of the stub, and the defect of the wiring length. Further, regarding the disconnection, the short, and the stub, it is possible to indicate the position. . Therefore, the present invention can be used not only for inspection of ordinary printed wiring boards but also for inspection of printed wiring boards for ultra-high-speed electronic circuits.

For the same reason, it is not necessary to simultaneously probe at least two points of the voltage application point and the voltage measurement point as in the conventional example of FIG. 15, and it is sufficient to probe only one point. When inspecting the wiring, it is not necessary to probe the front and back surfaces of the printed wiring board. Therefore, it is possible to avoid an increase in size, complexity, and cost of the device.

In this embodiment, the multi-probe head 24
Is moved, and the measurement is sequentially performed locally, so that the pressure applied to the printed wiring board 31 can be reduced, and the breakage thereof can be prevented.

Further, in the present embodiment, since a plurality of probes 28 are selected using the coaxial multiplexer 22, a printed wiring board having measurement points of the same pattern, for example, as shown in FIG. In order to mount a plurality of IC chips 29 having the same size and the same shape, it is suitable when inspecting the wiring 32 of the printed wiring board 31 formed by forming the bonding pad group 30 of the same pattern on each IC chip mounting portion. is there.

[Effects of the Invention] As described above, according to the present invention, a step pulse is applied to a wiring, the waveform of the reflected wave is measured, and the quality of the wiring can be determined by analyzing the waveform. It can be used to inspect printed wiring boards for ultra-high-speed electronic circuits by making it possible to detect characteristic impedance defects, the presence of stubs, and wiring length defects as well as disconnections and short circuits, and printed wiring for surface mounting. Avoiding the increase in size, complexity and cost of the equipment by enabling inspection from one side of the board, and reducing the number of probes and the pressure applied to the printed wiring board by reducing the pressure on the printed wiring board Damage can be prevented.

[Brief description of the drawings]

1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a schematic perspective view of the same, and FIG. 4 is a rear view showing a multi-probe head. a plan view Fig. 5 showing the printed wiring board, FIG. 6 is a diagram for explaining the waveform of the reflected wave S _B, the reflected wave in the case where there is no defect in Figure 7 A~D each wire
Shows the waveform of the S _B, Figure 8 Figure showing the position of a disconnection (a pattern disconnection), Figure 9 shows the waveform of the reflected wave S _B in the case where there is a break in the pattern unit figures, FIG. 10 break shows the position of (through hole disconnection), FIG. 11 shows the waveform of the reflected wave S _B in the case where there is a break in the through hole portion, the reflected wave when FIG. 12 there is a defect in the characteristic impedance
Shows the waveform of the S _B, FIG. FIG. 13 showing the position of the stub, Fig. 14 shows the waveform of the reflected wave S _B in the case where there is a stub FIG, FIG. 15 a conventional printed wiring board inspection apparatus FIG. 16 is a rear view showing a nail bed. 10: Multi-probe head 11: Multi-probe head moving means 12: Multi-probe head movement control means 13: Wiring design data storage means 14: Measurement point indicating means 15: Step pulse application / reflection waveform measuring means 16 … Wiring quality judgment means 17… Printed wiring board 18… Wiring 19… Probe

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-155770 (JP, A) JP-A-61-262671 (JP, A) JP-A-59-90986 (JP, A) 33665 (JP, A) Japanese Utility Model Showa 63-107866 (JP, U) IBM Tech. Disclosure Bull. Vol. 26, No. 10 A, pp. 4945-4946, 1984

Claims (1)

(57) [Claims] 1. A multi-probe head (10) in which probes (19) are arranged in a bracket shape at regular intervals on a pin board (9), and the multi-probe head (10) is vertically, horizontally, A multi-probe head moving means (11) for moving in the height direction; and controlling the multi-probe head moving means (11) to move the multi-probe head (10) and to connect the probe (19) to the printed wiring board. A multi-probe head movement control means (12) for contacting a designated measurement point on the wiring (18) of (17); a wiring design data storage means (13) for storing design data of the wiring (18); Measuring point indicating means (14) for indicating the measuring point to the multi-probe head movement control means (12) based on the design data of the wiring (18) stored in the wiring design data storing means (13); The said _A step pulse application / reflection waveform measuring means (15) for applying a step pulse (S _A ) to the measurement point via a lobe (19) and measuring the waveform of the reflected wave (S _B ); Wiring quality determination means (15) analyzes the waveform of the reflected wave (S _B ) measured by the applied / reflected waveform measurement means (15), compares the result with the design data, and determines the quality of the wiring (18). 16) A printed circuit board inspection device, comprising: