JP4922666B2 - Printed wiring board manufacturing method and printed wiring board inspection pattern unit - Google Patents

Description

  The present invention relates to a method for manufacturing a printed wiring board having a film cover lay bonded thereto, and more particularly, to a method for manufacturing a printed wiring board having an inspection pattern used for quality determination of a printed wiring board having a film cover lay bonded thereto, and the manufacturing thereof. The present invention relates to an inspection pattern unit used in the method.

  In recent years, FPCs in which a flexible printed wiring board (hereinafter referred to as FPC) is covered with a film cover lay are frequently used in accordance with downsizing, lightening, thinning, and high density of electronic devices. Film coverlays have a conductive pattern sandwiched between substrate films to strengthen the adhesion between the conductive pattern and the substrate film, and prevent peeling and cutting of the conductive pattern when the FPC is repeatedly bent or displaced. To do. It also ensures electrical insulation when the FPC comes into contact with other parts and housings, and prevents moisture from entering and rusting.

In the manufacturing process in which the film cover lay is bonded to the FPC, the adhesive formed in advance on the film cover lay is softened by hot pressing, and this is caused to flow between the conductive patterns so as not to generate bubbles. However, in the bonding process, abnormalities such as bubbles and wrinkles are likely to occur between the FPC and the film coverlay.
For example, as shown in a part of the FPC in FIG. 6, bubbles 22 are generated between the conductive patterns 21. FIG. 6 shows a case where a large number of bubbles 22 are generated. The size of the bubbles 22 varies depending on the interval between the conductive patterns. Further, the location where bubbles are generated varies depending on the shape of the interval between the conductive patterns.
As described above, when bubbles or wrinkles are generated, the film cover lay does not sufficiently exert its effects such as a decrease in the adhesive strength of the film cover lay, a decrease in electrical insulation between the conductive patterns, and the occurrence of copper migration.

In order to solve this problem, Patent Document 1 discloses a method for suppressing the generation of bubbles.
In Patent Document 1, after a film cover lay having an adhesive layer is laminated on a wiring board having wiring formed on the surface of a base substrate, the wiring board and the film cover lay are temporarily attached, and then the main bonding is performed by a heating press. In this manufacturing method, the film coverlay is temporarily bonded to a place where air bubble extrusion is not hindered, and a film cover lay is temporarily attached, thereby preventing air bubble extrusion inhibition during the hot pressing in the main attaching step.
JP 2004-319686 A

By the manufacturing method described in Patent Document 1, an FPC with few or no bubbles can be manufactured.
However, it is necessary to inspect whether there is any abnormality such as bubbles or wrinkles in order to determine whether the FPC is good or bad. Since it is not known where and in what shape the bubbles and wrinkles are generated in the FPC, the presence or absence of bubbles and wrinkles must be inspected by visual recognition of the entire area of the FPC or pattern recognition using a camera. Furthermore, since FPCs having various complicated shapes exist, it takes time to confirm the FPC and the entire workpiece.

In addition, in the conventional inspection, the presence or absence of bubbles and wrinkles is inspected. However, since the phenomenon such as the distribution, shape and size of bubbles and wrinkles cannot be analyzed, an index for optimizing the processing conditions can be obtained. There wasn't. Also, the thickness of the adhesive layer of the film coverlay should be set so that the conductive pattern is at the center position between the printed circuit board and the film coverlay, and that the adhesive does not protrude from the printed circuit board and the film coverlay. It is desirable to make it as thin as possible. For example, it is desirable that the thickness of the adhesive layer of the film cover lay be equal to or less than the thickness of the conductive pattern layer of the FPC. However, when the thickness of the adhesive layer of the film cover lay is so thin, bubbles are likely to be generated at a place where the conductive pattern interval is large, and there are many problems to prevent the bubbles from being generated.
Also, the expiration date of the adhesive material for the film cover lay is usually several months (three months), and there is a difference in the embedding of the adhesive material depending on the usage period of the film cover lay. Could not set.
Furthermore, in the case of double-sided PPC, through-hole plating is performed, but since the thickness of the plating is different between the central portion and the peripheral portion of the workpiece, the film coverlay bonding conditions must be adjusted accordingly.

  In order to solve the above-described problems, the present invention provides a method for manufacturing a printed wiring board that can easily determine the quality of a product or workpiece as a whole and can simplify the work process. . Also, a method of manufacturing a printed wiring board that can grasp the tendency of phenomena such as bubbles, wrinkles, and distributions, shapes, and sizes, and can obtain an index of process optimization, and this manufacturing method The present invention provides a test pattern for a printed wiring board used in the manufacturing process.

In order to solve the above problems, the printed wiring board manufacturing method of the present invention includes a substrate pattern having a conductive pattern, and an inspection pattern having a pattern width and pattern interval smaller than the conductive pattern in the vicinity of the substrate pattern, A step of preparing a work in which an inspection pattern unit that is gradually changed to an inspection pattern having a pattern width and a pattern interval larger than the conductive pattern, and a step of attaching a film coverlay in which an adhesive layer is previously formed to the work; And a step of inspecting whether or not there is an abnormality occurring in the inspection pattern unit by the bonding.
Here, the printed board is a so-called single-sided FPC in which a conductive pattern is formed on one side of the printed board, but may be a double-sided FPC in which a conductive pattern is formed on both sides of the printed board. The vicinity of the substrate pattern is preferably the outer periphery of the substrate pattern to which the conductive pattern is applied. However, it may be formed in an empty area where the conductive pattern is not formed in the substrate pattern.
By having the above configuration, according to the present invention, the inspection pattern unit represents the entire conductive pattern in the substrate pattern, and the inspection area can be reduced, so that the work process can be simplified. . In addition, the tendency of phenomena such as the distribution, shape, and size of abnormalities such as bubbles and wrinkles can be grasped, and an index for optimizing the process can be obtained.

  The inspection pattern unit may be formed by combining an inspection pattern having a constant pattern width and a gradual change in pattern interval and an inspection pattern having a constant pattern interval and a gradual change in pattern width. By combining the inspection patterns in this way, an inspection pattern that is gradually changed from an inspection pattern having a pattern width and pattern interval smaller than the conductive pattern to an inspection pattern having a pattern width and pattern interval larger than the conductive pattern is comprehensively formed. Can be arranged. Therefore, all the various conductive patterns having different pattern widths and pattern intervals can be inspected. Furthermore, if the inspection patterns combined as described above are arranged in a matrix, abnormal inspection such as bubbles and wrinkles can be easily performed, and the location where the abnormality has occurred can be easily analyzed.

The pattern unit for inspection changes from an inspection pattern having a smaller pattern width and pattern interval to an inspection pattern having a larger pattern width and pattern interval than the conductive pattern having the smallest pattern width and the smallest pattern interval among the conductive patterns. It is good to form. As a result, the center value of the inspection object can be set to a conductive pattern with the strictest bonding conditions, and product inspection can be performed.
In addition, the inspection pattern unit may be formed on the discard plate portion of the workpiece around the outer periphery of the substrate pattern. Thereby, the substrate pattern is not enlarged.
A partial pattern in which the conductive pattern is partially formed may be disposed adjacent to the inspection pattern unit. Thereby, the product can be inspected by comparing the partial pattern and the inspection pattern unit.
In the printed wiring board of the present invention, the thickness of the adhesive layer formed on the film coverlay is preferably equal to or less than the thickness of the conductive pattern. As a result, the sticking out of the adhesive material is eliminated, and the conductive pattern can be set at a substantially central position between the printed board 2 and the film 6.

  Moreover, the printed wiring board of this invention detects the boundary where the said abnormality exists, and sets the bonding conditions of a film coverlay based on the detection result. As a result, according to the present invention, the tendency of phenomena such as the distribution, shape, and size of abnormalities such as bubbles and wrinkles can be grasped, so that an index for optimizing the process can be obtained. Then, the bonding process can be optimized by matching the index.

  According to another aspect, the present invention is an inspection pattern for a printed wiring board. When a film coverlay having an adhesive layer formed thereon is pasted on a work on which a plurality of substrate patterns having conductive patterns are formed. Further, an inspection pattern used for inspecting the presence or absence of an abnormality occurring in the inspection pattern is changed from an inspection pattern having a pattern width and pattern interval smaller than the conductive pattern around the substrate pattern to a pattern width and pattern interval smaller than the conductive pattern. The inspection pattern is formed by gradually changing to a large inspection pattern. According to the present invention, it is possible to determine the quality of a product based on the location where an abnormality such as bubbles or wrinkles exists, and to recognize an allowable value from an optimum condition.

  According to the present invention, since the inspection pattern unit represents the entire product or the entire workpiece, the inspection pattern unit can easily determine pass / fail and simplify the work process. In addition, the tendency of phenomena such as the distribution, shape, and size of abnormalities such as bubbles and wrinkles can be grasped, and an index for optimizing the process can be obtained.

Hereinafter, the printed wiring board of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross-sectional view of a printed wiring board according to an embodiment of the present invention. A flexible printed circuit board (FPC) 1 includes a board pattern in which a conductive pattern 4 is formed on a printed board 2 via an adhesive 3. On the other hand, the film coverlay 5 is obtained by applying an adhesive 7 to the film 6 in advance.
The printed board 2 and the film 6 are made of the same type of material, for example, a polyimide film, and the adhesives 3 and 7 are made of the same type of material, for example, an acrylic resin or an epoxy resin.
The printed circuit board 2 has a thickness of 25 μm, for example, and the conductive pattern 4 has a thickness of 18 μm, for example. For example, the film 6 having a thickness of 12.5 μm is used, and the thickness of the adhesive 7 formed on the film cover lay 5 is, for example, 15 μm.
In the present invention, the adhesive 7 is formed to be thinner than the thickness of the conductive pattern 4. In this way, the same kind of material is used as the adhesives 3 and 7, and the thickness of the adhesive layer of the film coverlay is made equal to or less than the thickness of the conductive pattern, so that the conductive pattern is formed between the printed circuit board 2 and the film 6. It can be positioned approximately in the middle.

FIG. 2 shows a plan view of a work 11 for manufacturing the printed wiring board of the present invention. In FIG. 2, the film coverlay 5 is seen through and a surface view of the work 11 is shown.
As shown in FIG. 2, the workpiece 11 is formed by dividing a substrate pattern 12 having a conductive pattern 4 into six blocks. An inspection pattern unit 13 is formed in the vicinity of each substrate pattern 12. In FIG. 2, a total of 12 inspection pattern units 13 are formed in the corners of each substrate pattern 12 on the discard plate portion 14. Further, a partial pattern 15 representing the conductive pattern formed in the substrate pattern is formed on the discard plate portion 14 adjacent to the inspection pattern unit 13. The partial pattern 15 is formed to have a typical pattern width and pattern interval for forming the conductive pattern 4 and is provided for comparison with the inspection pattern unit 13, and it is not necessary to form a circuit.
The number of substrate patterns 12 formed on the workpiece 11 is not limited to that shown in FIG. 2, and may be set as appropriate according to the size of the workpiece 11 and the size of the substrate pattern 12. It does not matter. Further, the number of the pattern units for inspection 13 and the partial patterns 15 is not limited to that shown in FIG. 2, and may be larger or smaller. Further, although not shown, the inspection pattern unit 13 and the partial pattern 15 may be formed in an empty area of the substrate pattern 12. Further, the inspection pattern unit 13 and the partial pattern 15 are not necessarily formed in pairs, and may be formed independently.

FIG. 3 is a diagram for explaining the details of the inspection pattern unit 13. The test pattern units 13 are formed simultaneously with the pattern formation of the conductive pattern 4, and 12 test pattern units 13 shown in FIG. 3 are formed on one work as shown in FIG. .
As shown in FIG. 3, the test pattern unit 13 forms four test patterns 21a to 21d having a constant pattern interval and a gradually changing pattern width in the x-axis direction, the pattern width is constant, and the pattern interval is Four test patterns 22a to 22d that gradually change are formed in the y-axis direction, and are further formed by regularly combining them in a matrix in the x-axis and y-axis planes.

In the inspection patterns 21a to 21d in FIG. 3, the pattern interval is 20 μm, and the pattern width changes every 10 μm from 20 μm to 50 μm. The inspection patterns 22a to 22d have a pattern width of 20 [mu] m and a pattern interval that changes every 10 [mu] m from 20 [mu] m to 50 [mu] m. Therefore, an inspection pattern is formed in which the pattern pitch (total of pattern width and pattern interval) gradually changes in the upward direction in FIG.
In FIG. 3, an index 23 indicating the pattern width and the pattern interval with numerical values is displayed for each inspection pattern. In addition, numbers (L1 to L4) indicating the position of the inspection pattern are displayed in the vertical direction outside the inspection pattern group 13, and numbers (P5 to P7) indicating the pattern pitch are displayed in the upper horizontal direction. And the number (S1-S4) which displays a position in a test | inspection pattern and the number which shows a pattern pitch are respectively displayed in the lower horizontal direction.
Thus, by displaying the numbers in the respective parts, it is possible to specify as numerical data the location where an abnormality such as a bubble or wrinkle has occurred.
The inspection pattern unit 13 in FIG. 3 forms an inspection pattern whose pattern pitch changes from 40 μm to 100 μm. The auxiliary lines indicated by the dotted lines in FIG. 3 indicate the pattern pitch classification lines every 10 μm.

The inspection pattern unit 13 shown in FIG. 3 is merely an example, and the present invention is not limited to this. The number of inspection patterns, the pattern width, and the pattern interval can be arbitrarily set. However, it is desirable that the center value of the pattern unit for inspection 13 is matched with the smallest conductive pattern width and pattern interval among the conductive patterns.
For example, in the example of FIG. 3, the conductive pattern has the smallest pattern width of 40 μm and the pattern interval of 40 μm, and therefore the pattern pitch is 80 μm, and the inspection pattern (21c, 22b) indicated by the index (L40 / S40). Corresponds to this. If a special mark, for example, a frame or color surrounding the inspection pattern, is added to the inspection target pattern, the inspection becomes easier at the time of the inspection process. As a result, the conductive pattern having the smallest conductive pattern width and pattern interval can be inspected in three steps smaller than that and in two steps larger than that.

Next, the manufacturing method of the printed wiring board of this invention is demonstrated in order of a process.
FIG. 4 is a process diagram for explaining the method of manufacturing a printed wiring board according to the present invention in the order of steps. First, in step S1, a polyimide film is prepared as a material for the printed circuit board 2. In step S2, a rolled copper foil is laminated on one side with an adhesive, and in step S3, the workpiece 11 is cut into a predetermined size. Form. Next, in step S4, a through hole is drilled, and in step S5, the through hole is plated.
Thereafter, in step S6, a dry film is attached to one side of the work 11, and in step S7, exposure and development are performed with the substrate pattern 12 having the predetermined conductive pattern 4, the inspection pattern unit 13 and the partial pattern 15 in FIG. To form a resist film. Next, in step S8, etching is performed, and then the resist film is removed. As a result, the test pattern unit 13 and the partial pattern 15 are formed simultaneously with the formation of the substrate pattern 12.

Next, in step S9, a work 11 on which the substrate pattern 12, the inspection pattern unit 13 and the partial pattern 15 are formed as described above is prepared, and the film coverlay 5 with an adhesive is superimposed on the work 11. In step S10, hot pressing is performed. Thereafter, in step S11, the presence or absence of abnormality such as bubbles or wrinkles in the inspection pattern unit 13 is inspected. Since the polyimide film used for the printed circuit board 2 and the film 6 is usually transparent or translucent, the presence or absence of abnormalities such as bubbles and wrinkles can be confirmed by visual observation.
When automating this inspection process, it is possible to configure an abnormal inspection apparatus by photographing the work surface with a camera and recognizing the image.
As a result of the inspection, if the inspection pattern that has abnormalities such as bubbles or wrinkles exists only in the pattern width and pattern interval smaller than the inspection target pattern, the substrate pattern on which the conductive pattern is formed is determined to be an acceptable product. Then, the substrate pattern is punched out in step S12, and a finished product is obtained in step S13.

  FIG. 5 shows the test results for the presence / absence of abnormality, where single circles and double circles indicate test patterns in which no bubbles are generated, and x marks indicate test patterns in which bubbles are generated. As shown in FIG. 5, when a film cover lay is pressure-bonded to a work on which a substrate pattern having a conductive pattern is formed, where the pattern width of the conductive pattern is wide and the pattern interval is narrow, the flow amount of the adhesive from the film cover lay In many cases, since the pattern interval is narrow, the adhesive is sufficiently distributed, so that bubbles and wrinkles are less generated. On the other hand, where the pattern width is narrow and the pattern interval is wide, bubbles and wrinkles are likely to occur because the amount of adhesive flowing from the film coverlay is small and the pattern interval is wide.

  As a result, in step S14, as shown by lines A and B, the pass / fail judgment line can be confirmed. Line A indicates a pass line, and line B indicates a pass line including an allowable value. That is, it can be seen that the line A does not depend on the pattern interval and the pattern width may be 40 μm or more. A pattern having a pattern width of 30 μm and a pattern interval of 20 μm was acceptable. It can be seen that the line B does not depend on the pattern interval and the pattern width may be 50 μm or more.

Based on the pass line A or B, in step S15, hot press conditions are set. For example, the press bonding time, heating temperature, and pressurizing force of the hot press are changed. Or it is made to correspond to the expiration date of the adhesive material of a film coverlay.
Alternatively, the thickness, uncured viscosity, and adhesive material of the film coverlay are changed. Alternatively, the design of the conductive pattern is changed, and the pattern width and pattern interval are changed so as to coincide with the pass line A or B. Alternatively, the thickness of the conductive pattern is changed. Any other conditions can be changed to match the passing line A or B. Alternatively, the pass line A or B is changed to a condition for moving in the vertical direction or the horizontal direction in FIG.
If the inspection target pattern (21c, 22b) having the smallest pattern width and pattern interval among the conductive patterns formed on the substrate pattern 12 is included in the left side area of the line A or B, the substrate pattern 12 Can be judged as bad. However, if the inspection target pattern (21c, 22b) is included in the region on the right side of the line A or B, the substrate pattern 12 can be determined as a non-defective product.
In the case illustrated in FIG. 5, the inspection target patterns (21c, 22b) corresponding to the substrate pattern 12 are in the right region of the line A and are determined to be non-defective products.

As described above, after one or more of the manufacturing conditions are newly set, the process returns to the step of FIG. 4 to check whether or not the newly set condition is appropriate by checking whether there is an abnormality. If appropriate manufacturing conditions are set, the yield rate can be improved by manufacturing under the new manufacturing conditions. However, if the manufacturing condition is not appropriate, another manufacturing condition is set, and the suitability of the manufacturing condition is determined.
By repeating such an operation, it can be manufactured under a manufacturing condition with a high yield rate.

Sectional drawing of a printed wiring board is shown. The top view of a printed wiring board is shown. The top view of the pattern unit for a test | inspection is shown. The manufacturing process figure of a printed wiring board is shown. The top view after the test | inspection of the pattern unit for a test | inspection is shown. The figure explaining a mode that a bubble generate | occur | produces between conductive patterns is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flexible printed circuit board 2 Printed circuit board 3 Adhesive material layer 4 Conductive pattern 5 Film coverlay 6 Film 7 Adhesive material layer 11 Work 12 Substrate pattern 13 Inspection pattern unit 14 Discarding plate part 15 Partial pattern 21, 22 Inspection pattern

Claims (6)

Inspection in which a substrate pattern having a conductive pattern and an inspection pattern having a pattern width and pattern interval smaller than the conductive pattern in the vicinity of the substrate pattern are gradually changed from an inspection pattern having a pattern width and pattern interval larger than the conductive pattern. Preparing a workpiece on which a pattern unit is formed;
Bonding the film coverlay having an adhesive layer previously formed on the workpiece;
A step of inspecting the presence or absence of an abnormality occurring in the inspection pattern unit by the bonding,
The inspection pattern of the inspection pattern unit is from the inspection pattern having the smallest pattern width and the smallest pattern interval to the inspection pattern having the smallest pattern width and the smallest pattern interval to the inspection pattern having the larger pattern width and the pattern interval. A plurality of first inspection patterns which are formed by changing the pattern interval and the pattern width is gradually changed are arranged in the x-axis direction, the pattern width is constant and the pattern interval is gradually changed. Are arranged in a matrix in the x-axis direction and the y-axis direction, a pattern pitch number is displayed in the x-axis direction, and a pattern is formed in the y-axis direction. A printed wiring board manufacturing method characterized by displaying a position number.   2. The method for manufacturing a printed wiring board according to claim 1, wherein the pattern unit for inspection is formed in a discarded plate portion of the work around the outer periphery of the substrate pattern.   3. The method of manufacturing a printed wiring board according to claim 1, wherein a partial pattern in which the conductive pattern is partially formed is disposed adjacent to the inspection pattern unit.   The method for manufacturing a printed wiring board according to claim 1, wherein a thickness of the adhesive layer formed on the film cover lay is equal to or less than a thickness of the conductive pattern.   The printed wiring board manufacturing method according to any one of claims 1 to 4, wherein a boundary where the abnormality exists is detected, and a film coverlay bonding condition is set based on the detection result. Method. The inspection pattern used for inspecting the presence or absence of an abnormality occurring in the inspection pattern when the film coverlay having the adhesive layer formed in advance is bonded to the work on which the plurality of substrate patterns having the conductive pattern are formed, Among conductive patterns, the pattern width is the smallest and the pattern interval is smaller than the conductive pattern with the smallest pattern interval . A plurality of first inspection patterns whose pattern width is gradually changed are arranged in the x-axis direction, and a plurality of second inspection patterns whose pattern width is constant and whose pattern interval is gradually changed are arranged in the y-axis direction. Are further combined and formed in a matrix in the x-axis direction and y-axis direction. Display Npitchi number, test pattern unit of the printed wiring board, characterized in that displaying the pattern position number in the y-axis direction.

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