JPH0758174A - Inspection method of printed-wiring board - Google Patents

Abstract

PURPOSE:To sense easily and accurately the dimensional accuracy of the width of a wiring pattern, in the inspection method of a printed-wiring board whereby the dimensional error of the wiring pattern after the etching treatment of the printed-wiring board is performed is sensed. CONSTITUTION:Terminals 21a, 21b of a measurement terminal unit 21 are fixed on a fixation member 21c in the state wherein the end parts of the terminals 21a, 21b are separated from each other by a distance L. When the accuracy of the pattern printing of a printed-wiring board is sensed, first, a measurement operator contacts the end parts of the terminals 21a, 21b respectively with the arbitrary places present on a pattern 11, and then, measures a resistance value R1 between the terminals 21a, 21b on the pattern 11. Subsequently, the measurement operator contacts the end parts of the terminals 21a, 21b respectively with the arbitrary places present on a pattern 12, and then, measures a resistance value R2 between the terminals 21a, 21b on the pattern 12. After the measurements of the respective resistance values R1, R2 are made possible, based on these values, simultaneous equations are created, and an error DELTAW of the width of the pattern is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a printed wiring board for detecting the accuracy of a wiring pattern after etching the printed wiring board, and more particularly to a printed wiring board for detecting the width dimension accuracy of the pattern. Regarding inspection method.

[0002]

2. Description of the Related Art In recent years, as the density of electronic circuits has increased, the wiring patterns of printed wiring boards on which components are mounted have become complicated. For this reason, if the accuracy of etching the wiring pattern is poor, short circuits between the patterns and decrease in conductivity may be caused.

Therefore, conventionally, in order to detect the accuracy of etching, the finished printed wiring board is cut, its cross section is polished, and the width dimension of the wiring pattern is directly measured using an optical microscope or the like. It was

However, with such a method, the dimension of the cut portion can be accurately measured, but since only a very small part of the pattern is seen, it is not possible to detect the variation in accuracy within a certain range. It was Further, since it takes time to cut and polish, the work efficiency is poor.

Therefore, the present applicant has already filed Japanese Patent Application No. 5-14.
According to No. 6078, two test patterns that are close to each other and have sufficiently different widths are formed on the same printed wiring board, and the resistance value between any two points on the test pattern is detected in each test pattern. , Provides a technology for detecting the dimensional accuracy by comparing two measured resistance values.

[0006]

However, in this technique, in order to accurately know the distance between the measurement points of the resistance value, precise measurement is necessary, or the measurement point is determined in advance in the test pattern and the position is set to that position. It was necessary to provide a drawer pattern, marks, etc.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for inspecting a printed wiring board that can easily and accurately detect the dimensional accuracy of the width of a pattern. .

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a method of inspecting a printed wiring board for detecting the width dimension accuracy of a wiring pattern after the etching of the printed wiring board. The first test pattern and the second test pattern, which are close to each other and have sufficiently different widths, are formed on the wiring board, and the resistance measuring device in which the distance between the resistance measuring terminals is fixed is used. Any 2 on the test pattern and the second test pattern
There is provided a method for inspecting a multilayer printed wiring board, which comprises detecting resistance values between points and comparing the detected two resistance values to detect dimensional accuracy.

[0009]

Using a resistance measuring device in which the first test pattern and the second test pattern which are close to each other and have sufficiently different widths are formed on the same printed wiring board and the distance between the resistance measuring terminals is fixed is used. Then, the resistance value between any two points on the first test pattern and the second test pattern is detected, and the detected two resistance values are compared to detect the dimensional accuracy.

For each resistance value, a theoretical formula can be established from the distance between two points on each pattern which is known in advance, the design dimension, and the error value of the width after manufacturing. At this time, since the first test pattern and the second test pattern are close to each other, the error value of the width can be considered to be almost the same. Therefore, the simultaneous equations can be solved for the error values by setting the error values of the widths in both theoretical expressions to the same variable.

At this time, since the distance between the resistance measuring terminals is fixed, an accurate numerical value can be obtained without making a precise measurement to know the distance between the measuring points or forming a special mark or pattern. Can be used.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a plan view showing a schematic configuration of the multilayer printed wiring board of this embodiment. The multilayer printed wiring board 1 is formed by laminating a plurality of glass epoxy type substrates having pattern wiring on both sides with a prepreg interposed therebetween. The multilayer printed wiring board 1 is mostly occupied by the circuit pattern portion 2 in which the pattern wirings are laminated. A test pattern portion 3 is provided near the edge of the multilayer printed wiring board 1. In this test pattern section 3,
One or more sets of test patterns are formed on each layer.

FIG. 3 is a diagram showing an example of a test pattern having the most basic structure. The test pattern 10 is composed of two patterns 11 and 12. The patterns 11 and 12 are provided so close to each other that they can be considered to have substantially the same dimensional accuracy. The pattern 11 is a thin linear pattern of about 0.1 mm.
2 is a thick linear pattern of about 1 cm. These patterns 11 and 12 can be used for any two patterns using a resistance measuring instrument.
The resistance values R1 and R2 between the points can be measured respectively.

FIG. 1 is a schematic view showing a method for inspecting a printed wiring board according to this embodiment. In this embodiment, the two terminals 21a and 21b of the measuring terminal unit 21 are brought into contact with the patterns 11 and 12, and the resistance measuring device 22 is used to make the terminal 21.
The resistance value between a and 21b is measured. Measuring terminal unit 2
1 is two terminals 21a, 21b and a fixing member 21c
It consists of The terminals 21a and 21b are fixed to the fixing member 21c in a state in which the distance between their distal ends is L.

In order to detect the accuracy of pattern printing on a printed wiring board, the measurer first contacts the tip portions of the terminals 21a and 21b at an arbitrary position on the pattern 11 and connects the terminals 21a and 21b on the pattern 11 to each other. The resistance value R1 is measured. Then, the terminal 2 is placed at an arbitrary position on the pattern 12.
The tip portions of 1a and 21b are brought into contact with each other, and the resistance value R2 between the terminals 21a and 21b on the pattern 12 is measured. When the resistance values R1 and R2 can be measured, the error ΔW of the pattern width is calculated based on these values by the following procedure.

Here, the design value of the width of the pattern 11 is W
1, the design value of the width of the pattern 12 is W2, the error value from the design value of each width of the patterns 11 and 12, the thickness, and the volume conductivity are ΔW, t, and ρ, respectively, the distance L on each pattern is L. The respective resistance values R1 and R2 of R can be expressed as R1 = ρL / t (W1 + ΔW) ... (1) R2 = ρL / t (W2 + ΔW) ... (2). Since the patterns 11 and 12 are so close to each other that the dimensional accuracy can be considered to be almost the same, both ΔW and t can be considered to be the same. If the conductive material used for the pattern is uniform, the volume conductivity ρ can be the same.
Furthermore, since the resistance measurement distance L is the same, ρ, t, and L can be eliminated by solving for ΔW from equations (1) and (2), and ΔW = (R2W2-R1W1) / (R1- R2) (3) That is, the width error value ΔW can be easily calculated from the width dimensions W1 and W2 known in advance and the measured resistance values R1 and R2.

As described above, in this embodiment, the two patterns 11 and 12 having different widths which are close to each other are formed and the resistance values R1 and R2 are measured through the measuring terminal unit 21, so that the respective layers are measured. The error value ΔW of the width of the wiring pattern can be easily and accurately obtained.

Incidentally, the resistance values R1 and R2 are measured by using FIG.
As shown in, the 4-terminal measurement terminal unit 31 may be used as the measurement terminal unit. The four-terminal measuring terminal unit 31 is composed of four terminals 31a to 31d fixed to a fixing member 31e. Terminal 31a,
31b is a terminal for supplying current, and terminals 31c and 31d
Is a terminal for measuring a voltage value. The terminals 31c and 31d are provided inside the terminals 31a and 31b, and are fixed such that the distance between the terminals is L, for example.

The resistance values R1 and R2 of the patterns 11 and 12 are measured by the 4-terminal measuring terminal unit 31 having such a configuration.
When measuring, use a 4-terminal resistance measuring instrument such as a Kelvin clip. As the measurement procedure, first, each terminal 31
The pattern 11 or the pattern 12 is attached to the tip of a to 31d.
Contact. Then, while a constant current is passed between the terminals 31a and 31b from a four-terminal resistance measuring device (not shown),
The voltage value between the terminals 31c and 31d at this time is measured.
Thereby, the resistance values R1 and R2 of the distance L on the patterns 11 and 12 are obtained from the supplied constant current value and the measured voltage value. Therefore, the resistance value can be easily and accurately measured in milliohm units.

In this embodiment, the test pattern portion 3
Was provided on a part of the multilayer printed wiring board 1,
In order to improve the inspection accuracy, a large number may be provided in the circuit pattern portion 2 or the like.

Further, in this embodiment, the patterns 11 and 12 are
Although the shape of is a straight line, it may be another shape such as an arc. Furthermore, the test pattern 10 can be applied not only to a multilayer printed wiring board but also to a single printed wiring board.

[0022]

As described above, according to the present invention, the resistance value between any two points on the pattern is detected by using the resistance measuring device in which the distance between the resistance measuring terminals is fixed, and based on the detected value. Since the dimensional accuracy of the pattern is detected, accurate error detection can be performed without performing precise measurement to know the distance between the measurement points or forming a special mark or pattern.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a method for inspecting a printed wiring board according to this embodiment.

FIG. 2 is a plan view showing a schematic configuration of a multilayer printed wiring board of this embodiment.

FIG. 3 is a diagram showing an example of a test pattern having the most basic configuration.

FIG. 4 is a diagram showing a schematic configuration of a 4-terminal measurement terminal unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer printed wiring board 2 Circuit pattern part 3 Test pattern part 10 Test pattern 11, 12 pattern 21 Measuring terminal unit 21a, 21b terminal 21c Fixing member 22 Resistance measuring instrument

Claims (2)

[Claims] 1. A method for inspecting a printed wiring board for detecting the width dimension accuracy of a wiring pattern after etching the printed wiring board, wherein the first printed wiring board is close to each other and has a sufficiently different width. Of the first test pattern and the second test pattern by using a resistance measuring instrument in which the distance between the resistance measuring terminals is fixed by forming the test pattern and the second test pattern of The resistance value of each of the two is detected, and the dimensional accuracy is detected by comparing the two detected resistance values with each other. 2. The method for inspecting a printed wiring board according to claim 1, wherein a 4-terminal resistance measuring device is used for measuring the resistance value.