JPS5833890A - Method and device for inspecting circuit pattern of printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for inspecting defects in wiring patterns (hereinafter also referred to as "route patterns") formed on printed wiring boards.

The appearance and structure of a general printed wiring board II are shown in Figs. Figure 2 is the same as Figure 1.
It is a cutaway diagram along line A'. In these figures, 4.
5 is a wiring pattern made of copper conductive foil; 6 is a through hole for electrical connection with the wiring surface 3 on the back side;
Reference numeral 7 denotes an insulating base material, and 13 and 14 denote inner layer patterns used as a ground layer and a power supply layer, which, like the wiring patterns 4 and 5, are made of conductive foil such as copper. The wiring pattern shown in Fig. 1 is generally created by copying the patterns (indicated by 4, 5, etc. in Fig. 1) onto a steel foil using a photographic master plate (mask) as an etching register F pattern, and then etching this. It is formed. During this formation process, if dust adheres to the photographic original plate or scratches occur on the photographic original plate, minute adhesion 8, minute chipping 9, minute protrusion 10 of the pattern will occur.
Insufficient etching causes the pattern to thicken 11, while excessive etching causes the pattern to become thinner 12. If these defects exist, microchips 9 and thinning 12 may increase circuit resistance, reduce current capacity, and disconnection due to contact when handling printed wiring boards, and microadhesions 8, microprotrusions 10, and thickening 11 may cause circuit short circuits. During soldering, solder bridges may occur, making it impossible to construct the correct wiring path as intended for the printed wiring board. These defects can be avoided especially in recent years when high-density packaging is thoroughly implemented, for example, when the pattern width is Q, 1 mm.
When reaching the Q degree, even the slightest defect must be accurately inspected without missing it, and visual inspection is no longer possible. Therefore, in order to perform such an inspection by a machine, as shown in FIG. There is a method of capturing the reflected light from the IITM as an optical image and comparing and comparing the images. This conventional method will be explained below.

FIG. 3 is a schematic diagram showing a conventional circuit checker for printing 1111 plates.

In No. $vAK, except for the electric signal comparison and verification device 27,
Components with the same configuration are arranged on the left and right, and each portion on the right side corresponding to each portion on the left side (printed wiring board to be inspected @) is marked with the same reference numeral and a dash. Therefore,
Functions of each part on the right.

The explanation of the operation can be replaced by adding a dash to the reference numerals in the explanation of the function and operation of each part on the left side, so only the explanation on the left side will be given as a representative. Now, above the wiring surface 2 of the printed wiring board 1, the light from the light source 21 applied from the side is reflected and irradiated onto the wiring surface 2, and the reflected light from the wiring W752 is passed upward.6 Bars 7 Mirrors 23 A lens 24 collects the light passing upward from the mirror 23 and forms an optical image, and an image sensor 25 is provided at the position where the optical image is formed, which converts the brightness and darkness of the image into a large number of electrical signals 26. A comparison and verification device 27 is provided which recognizes and compares and compares the electrical signal 26 obtained from the left image sensor 25 and the electrical signal 26' obtained from the right image sensor 25' as wiring patterns. The device 27 indicates the presence or absence of a gap and the defective location. For example, when inspecting a printed wiring board with a cross section structure as shown in FIG. 4 (Maro), the light emitted from the light source 21 in FIG. Each portion of the wiring surface 2 of the printed wiring 1 [1 is irradiated as light rays 31, 32, and 33 in FIG. 4(a). The light ray 31 has a low level of reflected light 4 due to the low reflectance of the insulating base material 7.
1, and the light ray 32 produces a high level of reflected light 42 due to the high reflectance of the wiring pattern 5 made of metal such as copper, and the light ray 33 passes through the through hole 6 to the back wiring surface 3.
Since the light passes through the rays, no reflected light occurs. The rays 41 and 42 reflected in one direction under such pressure are reflected by the half mirror shown in Fig. 3.
23, and is focused on the image sensor 25 via the lens 24 as an optical image. The image sensor 25 has a large number of microscopic light receiving elements arranged in a straight line, for example, a sensor having a length Kl of 13 mm and 024 elements arranged in a line.

Figure 4) is a plot of the electrical signals that appear when the reflected light 41 and 42 of Figure 4 (hot) are imaged on such an image sensor 25i1 for all light receiving elements, and the vertical axis is The electric signal level I is taken, and the horizontal axis represents the element position of the image sensor.

In the figure, 1 indicates the electrical signal level at the through hole position, which is at a low level because there is almost no reflected light from the wiring surface 2. (2) The reflected light 41 from the insulating base material 7 is converted into an electrical signal, and although it is higher than 11, it is still at a low level. I3 is a signal obtained by converting the reflected light 42 from the wiring pattern 5 into an electrical signal, and has a high level. In order to facilitate comparison and verification of these various levels, it is necessary to convert them into two types, a bright level and a dark level, that is, into binary values. For this reason, as shown in Fig. 4, a binarization circuit 28 consisting of a comparator, for example, is used to set the electrical signal level higher than the threshold level 8 as a bright level, and below it as a dark level. After conversion, wiring pattern 5 becomes bright level (binary @
1"), the insulating base material 7, and the through hole 6 are converted into a binary signal of the dark level (binary @"0"). The binary signal obtained in this way is generated when the light receiving surface of the image sensor 25 Since it is linear, it is line information (linear information such as when the pattern in Figure 1 is viewed along line A-A').Therefore, when the printed wiring board is moved in parallel along the wiring surface, Then, by storing the binary signal in the memo 929, surface information can be obtained in the memory 29. Thereafter, the two sets of left and right surface information stored in the memory 29 are stored in the pattern ratio soft circuit 30. Compare and match and display any parts that do not match as defects.

According to the conventional inspection equipment as explained above,
), when there is discoloration or dirt 15 on the surface of the wiring pattern 4.5, the reflected light 44 with respect to the incident light 34 at that part becomes extremely weak, as seen in FIG. As shown in Figure (e), in the electrical signal level plotted for all light receiving elements of the image sensor, the electrical signal level is low in the portion corresponding to discoloration and dirt 15 on the BB' cross section of the wiring surface 2, and Pelue 3. Therefore, what should originally be converted to a bright level is converted to a dark level by the binarization circuit 28, and even though it is simply a discolored or dirty wiring pattern, it may be mistaken for a defect. This results in a lower result. Therefore, in a conventional inspection device configured to detect a defect in a wiring pattern by capturing reflected light from a wiring surface, there is a problem in that the defect is incorrectly determined even though it is not a defect.

The purpose of the present invention is to eliminate the above-mentioned defects, distinguish pseudo defects such as discoloration of wiring patterns and stains from true defects, and
An object of the present invention is to provide a pattern inspection method and apparatus for a printed wiring board that can detect only true defects as defects.

The key point of the present invention is to irradiate the circuit pattern of a standard printed wiring board with bright line-shaped light, and to determine the shape of the circuit pattern from the reflected light image. By clearly identifying and memorizing the relative height position deviation with respect to the circuit pattern surface, the same operation is performed on the circuit pattern of the printed wiring board to be inspected to determine its shape. is similarly recognized and stored, and defects in the circuit pattern to be inspected are detected by comparing both stored contents.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 6 is a schematic diagram showing an embodiment of the present invention.

In Fig. 6, 51.51' is a light source, 52 and 52' are lenses, and 54.54' is a half mirror.
3' is a slit for irradiating the wiring surface 2.2' with slit light (bright line-shaped light). However, the light source is 51°51'
, lenses 52 and 52', slits 53 and 53', and half mirrors 54 and 54' are shown in this case as being arranged to irradiate the wiring surface 2 with slit light from above. The direction of irradiation is not limited to from above. Further, if the purpose of irradiating the slit light can be achieved by using another means, such as a prism or a mirror, that may be used. 55.55' is camera 56.5
6' is a lens for coupling, 56.56 is a camera. This camera can be replaced by parallel movement of the linear image sensor 25 and the printed wiring board shown in FIG. This is an electrical signal that can be output from the extraction circuits 57, 57'.

The other parts 27, 28, 28' and 29, 30 are the same as the parts with the same reference numerals in FIG. 3, so their explanations will be omitted here. FIG. 7 is a perspective view clearly showing the configuration of the main parts in FIG. 6, and its operation will be explained using this.

Note that in Figure 6, items with the same reference numerals with a dash are the same as those without a dash, and their functions and operations are the same as those without a dash, so they are explained in Figure 7. omitted.

Now, in FIG. 7, the light emitted from the light source 51 is transmitted to the lens 52.
After passing through the slit 53 and becoming slit light (bright line-shaped light), the half mirror 54 irradiates the wiring surface 2 of the printed wiring board 1 from above. Therefore, the bright line 16 of the slit light exists at a position following the unevenness formed by the surface of the wiring pattern 5 and the surface of the insulating base material 7 on the wiring surface 2, and this bright line 16 is viewed from an oblique direction. Bright line 1 on the surface of wiring pattern 5 is captured by camera 56 through lens 55
6 and a bright line 16 on the surface of the insulating base material 7 located at a position one step lower than the bright line 16 can be regarded as a discontinuous bright line with a step difference. The bright line 16 on the surface of the wiring pattern 5 captured by the camera 56 is a bright line in which the slit light forms a strong contrast between light and dark, so it is hardly affected by discoloration or dirt on the wiring pattern. , which can be reliably detected. Therefore, FIG. 8 (
Discoloration and dirt on wiring pattern on wiring surface 2 of a) 15
Assuming that there is a bright line 16 on the B-B' edge line containing
A picture image as shown in FIGS. 8(C) and 8(K) is obtained which faithfully represents the unevenness of the wiring surface 2 shown in the cross-sectional view of FIG. 8(b). FIG. 8(C) The discontinuous horizontal line K indicates the bright line of the slit light, and the bright line corresponding to the level LIK is the bright line indicating the surface of the wiring pattern 5, and the level L! A bright line indicating the surface of the insulating base material 7 corresponds to the level L3, and a detail indicating the through hole 6 corresponds to the level L3. Here, if a frequency distribution of 91 levels is taken in the rask scan direction of the camera, a frequency distribution as shown in FIG. 8(d) is obtained. In other words, in figure (d), the threshold level 11 is set between the peak of the frequency of appearance of bright lines corresponding to level LIK and the peak of the frequency of appearance of bright lines corresponding to level L2. If the signal at the above level is taken as a signal representing the wiring pattern, then B on the wiring surface 2 of FIG.
- The position of the wiring pattern on the B' edge line can be accurately defined. Therefore, if the slit light is provided over the entire surface of the wiring surface 2 shown in FIG. 8(a) and captured by the camera 56, the wiring pattern on the wiring surface 2 can be accurately obtained.

According to the present invention, it is possible to accurately detect the shape of a wiring pattern without being affected by discoloration or dirt on the wiring pattern. However, compared to the conventional inspection method using reflected light, the present invention using slit light Since the detection speed of the above inspection method is very slow, it may not be suitable as a method for inspecting the entire wiring pattern, so in that case, it is better to use it together with the conventional method using reflected light. That is, first, a conventional inspection method using reflected light is carried out, and only for those wiring patterns that are determined to have defects, the inspection method using slit light according to the present invention is carried out to confirm that the defects are not simply discolored or dirty. ,
It is better to check whether it is a real defect or not.

In such a case, there will be no problem if the inspection device is equipped with both the conventional device as shown in FIG. 3 and the device according to the present invention as shown in FIG. Since there are many parts, you can omit part of one and use it for the other.

For example, the light source 51, 51' and the lens 52 in FIG.
, 52', half mirrors 54, 54', etc. may also be used as the light source 21, 21', lens 22, 22', and half mirrors 23, 23' in Figure @3. In this case, the light rays from the light source are ) It is necessary to provide a means for switching the optical path in order to convert the light into a slit light through K, or to project it directly onto the wiring surface without passing through the slit, but such a switching means can be easily installed. can.

As described above, according to the present invention, the following effects can be expected.

(1) First, defects in the wiring circuit are detected using the conventional method using reflected light, and only the areas where an abnormal pattern is extracted can be confirmed using the slit light according to the present invention, so the inspection speed is not slowed down so much.

(2) The method and device of the present invention for detecting bright lines of slit light eliminates false indication of defects due to discoloration or dirt in wiring circuits.

(3) New slit structure for slit light generation
Since the device of the present invention that reliably detects defects in wiring circuits can be constructed using only the lkff and a conventional inspection device using reflected light, the cost can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged plan view of a general printed wiring board, Fig. 2 is a sectional view taken along line A-A' in Fig. 1, and Fig. 3 is a conventional printed wiring board circuit pattern inspection device. FIG. 4 is an explanatory diagram of the inspection principle of the same device, FIG. 5 is an explanatory diagram of the process by which a wiring pattern is incorrectly determined to be defective when there is discoloration or dirt, and FIG. 6 is an explanatory diagram of the present invention. FIG. 7 is a perspective view showing the configuration of the main parts in FIG. 6 in an easy-to-understand manner, and FIG. 88 is a schematic diagram showing an embodiment of the present invention. FIG. 2 is an explanatory diagram of a process in which a defect is not erroneously determined due to i1. Symbol explanation 1.1... Printed wiring board, 2, 3... Wiring surface, 4, 5
...Wiring pattern, 7...Insulating base material, 15...Discoloration, dirty device, 28.28'...Binarization circuit, 29...
・Memory, 3°...Pattern comparison circuit, 31-35・
...Incoming light, 41-44...Reflected light, 53, 53'
...Slit, 56.56'...Camera, 57,
57 Mouse Cutting Line Extraction Circuit Agent Patent Attorney Akio Namiki Figure 1 Figure 2 Figure 3 Figure 30 Figure 4 Figure 5 (b) 1 Ino 27~1+, -9 Kushiko 3Jσy-! Figure 6 0 67 Figure 8

Claims (1)

[Claims] 1) Irradiate bright line-shaped light onto the circuit pattern of a standard printed wiring board, and determine the shape of the circuit pattern from the reflected light image at least on the insulating base material surface of the wiring board. There is a stage of clearly identifying and memorizing the relative height deviation with respect to the circuit pattern made of conductors, and a stage of performing similar operations on the circuit pattern of the printed wiring board to be inspected. A printed wiring board characterized by comprising a step of determining and storing a shape, and a step of detecting a defect in a circuit pattern of a printed wiring board to be inspected by comparing the two stored results. sea circuit pattern inspection method. 2) A stage in which the circuit pattern of the printed wiring board to be inspected is irradiated with light and the shape of the circuit pattern is memorized based on the magnitude of the amount of reflected light, and the circuit pattern of the printed wiring board to be inspected is a step of performing a similar operation on the printed wiring board to similarly recognize and memorize its shape; and a step of detecting defects in the circuit pattern of the printed wiring board to be inspected by comparing the two memorized results. A first circuit pattern inspection method consisting of: irradiating bright line-shaped light onto the circuit pattern of a standard printed wiring board, and determining the shape of the circuit pattern from the reflected light image;
At least a step of clearly identifying and recognizing and memorizing the relative height deviation between the insulating base material surface of the wiring board and the circuit pattern made of the conductor, and the circuit pattern of the printed wiring board to be inspected. A step of performing similar operations on the object to similarly recognize and memorize its shape, and a step of comparing the two memorized results to detect defects in the circuit pattern of the printed wiring board to be inspected. and a second circuit pattern inspection method consisting of the following: First, for the circuit pattern determined to be defective by performing the first circuit pattern inspection method, the second circuit pattern inspection method is performed to detect the true defect. A circuit pattern inspection method for a printed wiring board, characterized in that the circuit pattern is detected. 3) A bright line light source obtained by passing light from a light source through a slit, a means for irradiating bright line light from a skeleton light source onto a circuit pattern on a printed wiring board, and a method for determining the circuit pattern from the reflected light image. A means for recognizing the shape while clearly identifying the relative height position deviation between at least the insulating base material surface of the wiring board and the conductor/(turn surface), and a standard circuit pattern of the printed wiring board. a first storage means for binarizing and storing the recognition results obtained as described above for the circuit; and a recognition result similarly obtained as described above for the turn of the printing circuit 11 to be inspected. and a means for comparing the stored contents in the two storage means, and detecting a defect in the four-path pattern to be inspected from the comparison result. A circuit turn inspection device for printing layout S slope with 411 features.