JP2010182728A - Method of manufacturing flexible printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a flexible printed wiring board even if it has a large printing region, with which flaws in printing such as ink splash or blur are hard to occur on a print pattern in screen-printing solder resist and good printing quality can be assured. <P>SOLUTION: In the manufacturing method of the flexible printed wiring board 4 including a step of screen-printing the solder resist 9 on the flexible printed wiring board 4 having a wiring pattern formed, first a platelike protrusion 1 lower than a clearance value between a printing table 2 and a screen printing plate 8 is put on a predetermined position on an upper surface of the printing table 2 on a side where a squeegee 7 starts to slide or on a lower surface of the screen printing plate 8. Then, the flexible printed wiring board 4 is mounted on the printing table 2. The screen printing plate 8 is brought into contact at a clearance of 0.5 mm or larger. Thereafter, the squeegee 7 is slid, and the solder resist 9 is printed via the screen printing plate 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a flexible printed wiring board, and even when a flexible printed wiring board having a large printing area, such as a TCP (Tape Carrier Package) board or a COF (Chip On Film) board, is printed during solder resist screen printing. The present invention relates to a method for manufacturing a flexible printed wiring board, in which ink splattering and bleeding printing defects are unlikely to occur in a pattern and good printing quality can be secured.

  Flexible wiring substrates are widely used for refractive wiring in electronic devices and digital cameras that require refractive and bending characteristics such as hard disk read / write heads and printer heads. Insulating resin film base material such as polyimide film, polyamide film, PET film, etc., coated with conductive metal such as copper foil, is used to remove unnecessary metal layers to form a wiring circuit for circuit protection Further, a solder resist is printed on the surface of the film substrate.

Conventionally, in order to print a solder resist on a flexible printed wiring board, a screen printing machine has been used in the following manner. First, a solder resist that is a viscous material is placed on the screen plate, and the squeegee is slid along the upper surface of the screen plate. The solder resist is mainly composed of a thermosetting resin such as an epoxy resin or a polyimide resin, and is transferred onto a flexible printed circuit board through an emulsion opening formed in a screen plate serving as a printing pattern.
Then, the flexible printed wiring board with which the soldering resist was apply | coated is heat-processed, and a soldering resist is hardened.

  As a screen printing machine, for example, there is a printing machine proposed in Patent Document 1 shown below and shown in FIG. That is, in this screen printing machine, the holding unit 20 is provided on the positioning unit formed by stacking the Y-axis table 12, the X-axis table 14, the θ-axis table 16, and the Z-axis table 18. The wiring board 4 is placed with the board surface on which the wiring pattern is formed as an upper surface, and is held by a frame body 24 that can be raised and lowered by a clamper.

The screen plate 8 has an opening, and after being positioned on the wiring board 4, a pattern having a predetermined shape is formed on the wiring board 4 with ink applied by a squeegee 7 that can be moved up and down.
Further, a cleaning unit 34 for cleaning the lower surface of the screen plate 8 is provided on the side of the positioning portion, and the cleaning tape 40 is brought into contact with the wiring board surface side of the screen plate 8 and the take-up reel 38 from the supply reel 36. In this direction, the screen 32 is cleaned on the wiring board surface side.

  The board surface of the wiring board on which screen printing is performed is formed on the uneven surface by a wiring pattern. When screen printing is performed on the wiring substrate formed on the uneven surface, the screen plate 8 is attached to the substrate surface of the wiring substrate, and ink is applied while pressing the screen plate 8 with the squeegee 7. However, the screen plate 8 is pressed by the pressing force of the squeegee 7 as described above, but is not deformed following the shape of the wiring pattern. For this reason, in the vicinity of the edge of the opening as a pattern formed on the screen plate 8, a space is formed on the side of the wiring pattern located in the vicinity of the boundary of the printing area to be screen printed.

The printing ink applied by the squeegee 7 can easily enter the space from the edge of the opening as a pattern. For this reason, when the screen plate 8 is lifted from the substrate surface of the wiring substrate, an ink oozing portion is formed on the side of the wiring pattern, and the bleed extending on the back surface of the screen plate 8 from the edge of the pattern The protruding part is transferred.
When screen printing is repeated in a state where such a bleeding portion is generated, the bleeding portion of the screen plate 8 is enlarged, and the bleeding portion due to the transfer of the bleeding portion of the screen plate 8 is out of the printed area of the wiring board. Will occur. Thus, if a bleeding portion is generated outside the printed area of the wiring board, the wiring board does not become a product.

This phenomenon occurs when ink having low viscosity flows out from the opening 11 during printing and oozes out between the mask 8 and the substrate 4, so that the printing facing the substrate of the screen printing mask is performed. It has been proposed to provide an ink dam composed of a concave groove in the vicinity of the opening, which is an ink discharge part on the surface side (see Patent Document 2).
By providing the ink dam composed of the concave grooves, the ink that flows out from the opening of the mask and exudes between the mask and the printing material is held in the ink dam, so that the ink is placed outside the ink dam. It has become possible to prevent the ink pattern from being stretched and enlarged, or from partially breaking the ink pattern. However, when the printing area is enlarged, even if an ink dam is provided, the printing defect that occurs in the solder resist printing pattern cannot be sufficiently suppressed.

  The unit wiring pattern of the TCP or COF substrate is generally arranged in four rows of 35 mm width units or three rows of 48 mm width units on a long film having a width of 156 to 158 mm. The solder resist is printed collectively in a range of ˜144 mm × width 50 to 170 mm. The clearance (clearance) between the screen plate and the printing table requires a predetermined interval. For example, when a screen plate having a frame size of 320 to 450 mm square is used, the clearance may be set to 0.5 to 3.0 mm. It is common.

  In general, if the clearance is increased, the bleeding defect will decrease, but it will tend to cause splatter failure and scumming failure. Therefore, it is necessary to optimally set a well-balanced clearance while observing the occurrence of each defect, and it is difficult to reduce print pattern defects that occur in the printing process. In addition, with the increase in size of the print area, there is a problem that the print state is different between the end and the center of the print area.

  For this reason, even if the printing area is enlarged, it is possible to sufficiently suppress printing defects that occur in the solder resist printing pattern without adjusting the clearance between the screen plate and the printing table, ensuring good print quality. A possible method was eagerly desired.

JP 2004-122613 A Japanese Patent Laid-Open No. 10-329444

  In view of the above problems, the object of the present invention is that even a flexible printed wiring board having a large printing area such as a TCP board or a COF board causes ink splattering or smearing printing defects in the printed pattern during solder resist screen printing. It is difficult to provide a method for manufacturing a flexible printed wiring board that can ensure good print quality.

  The present inventor has intensively studied to solve the above-mentioned problems, a screen plate is brought into contact with the substrate with a clearance of 0.5 mm or more, and a solder resist is printed on the substrate through the screen plate. In the printing method, a plate-shaped protrusion having a specific size is provided on the front side of the printing table, and the protrusion is arranged at an optimal position, so that the occurrence of problems such as solder resist bleeding and solder resist scattering conflicts. The present inventors have found that it is possible to reduce the phenomenon together and have completed the present invention.

  That is, according to the first aspect of the present invention, in the method for manufacturing a flexible printed wiring board including the step of screen printing a solder resist on the flexible printed wiring board on which the wiring pattern is formed, first, on the squeegee sliding start side. A plate-shaped protrusion having a height lower than the clearance value between the printing table and the screen plate is attached to a predetermined position on the upper surface of the printing table or the lower surface of the screen plate, and then a flexible printed wiring board is mounted on the printing table. The screen plate in which the area other than the solder resist coating portion is masked by the emulsion is brought into contact with a clearance of 0.5 mm or more, and then the squeegee is slid and the solder is passed through the screen plate. Manufacture of flexible printed circuit boards characterized by printing resist The law is provided.

According to a second aspect of the present invention, in the first aspect, the flexible printed wiring board is a TCP (Tape Carrier Package) board or a COF (Chip On Film) board. A method for manufacturing a wiring board is provided.
According to a third aspect of the present invention, there is provided the method for manufacturing a flexible printed wiring board according to the first aspect, wherein the height H of the protrusion is 0.5 to 2.5 mm. Is done.
According to the fourth invention of the present invention, in the first invention, the width A of the protrusion is obtained from the height H of the protrusion as a calculated value W by the following expression (1), and the expression ( A method for producing a flexible printed circuit board, which satisfies the condition 2), is provided.
W = 20 · H ² −100 · H + 155 (1)
0.8W ≦ A ≦ 1.2W (2)
According to a fifth aspect of the present invention, there is provided a method for manufacturing a flexible printed circuit board according to the first aspect, wherein the length B of the protrusion is larger than the length of the solder resist coating region. Provided.
Furthermore, according to a sixth aspect of the present invention, in the first aspect, the protrusion is attached to the front side of the printing area, at a distance C of 40 to 60 mm, and the method for producing a flexible printed wiring board Is provided.

According to the present invention, it is possible to maintain good printability even when the printing area is enlarged, and it is possible to reduce defective phenomena such as solder resist bleeding and solder resist scattering that conflict with each other.
As a result, it is possible to satisfactorily produce a flexible printed wiring board having good print quality by improving the workability by forming a print pattern satisfactorily while applying the conventional printing conditions as they are.

It is the top view which showed typically the upper surface of the printing table in one Embodiment of this invention. It is a section side view showing typically the printing table in one embodiment of the present invention. It is the top view which showed typically the upper surface of the printing table in the conventional printing method. It is a section side view showing typically the printing table in the conventional printing method. It is a sectional side view showing typically the state where ink is applied to a wiring board by the conventional printing process. It is a side view which shows typically the cross section of a general screen printing machine in the conventional printing method.

  Preferred embodiments of the present invention will be described with reference to the drawings. The present invention relates to a method of manufacturing a flexible printed wiring board including a step of screen printing a solder resist on a flexible printed wiring board on which a wiring pattern is formed. First, the upper surface of a printing table on the squeegee sliding start side or the lower surface of a screen plate At a predetermined position, a plate-like protrusion having a height lower than the clearance value between the printing table and the screen plate is attached. Next, a flexible printed wiring board is placed on the printing table, and a portion other than the solder resist coating portion is placed. A screen plate whose area is masked with an emulsion is brought into contact with a clearance of 0.5 mm or more, and then a squeegee is slid and a solder resist is printed through the screen plate. .

(Embodiment 1)
In the present invention, in a printing machine on which a flexible printed wiring board on which a wiring circuit pattern is formed is set, first, as shown in FIG. 1, a protrusion having a predetermined size is formed on the printing table on the squeegee sliding start side. .

  The protrusion is formed using a material such as synthetic resin, light metal, or ceramic in the following manner. If it is a synthetic resin, it must be a hard material that is not easily deformed by an external force, and a hard resin such as hard polyurethane or methyl methacrylate is preferable. Even relatively soft resins such as polyethylene, polypropylene, and nylon can be mixed with inorganic powders such as glass powder and wollastonite, short fibers such as glass fibers and carbon fibers, or multilayered with long fibers. It may be hardened. The hardness is desirably 80 or more in Shore hardness (hardness measured by a Shore hardness tester which is a kind of repulsive hardness tester). This is because if the protrusion does not have a certain degree of hardness, the protrusion is repeatedly pressed against the screen plate with a squeegee during screen printing, so the protrusion deforms during printing, and the printing accuracy decreases due to the deformation. Because.

The method for forming the material to be the protrusion is not particularly limited, but usually, the raw material is injected or extruded into a mold having a predetermined size. When the protrusion is too high, or when the width or length of the protrusion is too large, the dimension is adjusted by cutting and cutting the formed plate-like body.
Examples of the light metal include an aluminum plate or an alloy plate of aluminum and zinc, tin, nickel, iron, or the like. In the case of a ceramic, a plate-like body such as glass or carbon is used.

  The length B of the protrusion is preferably longer than the printing area, and is preferably about the length of the printing area plus about 20 mm. If the length of the protrusion is not larger than the printing area, the same effect as when the clearance is locally increased cannot be obtained. Specifically, the length of the protrusion is preferably in the range of 50 to 170 mm, more preferably 60 to 150 mm.

The height H of the protrusion is set according to the clearance, and is preferably set to a size equal to or smaller than the clearance value, and is particularly preferably about 0.1 mm lower than the set clearance value. If it is larger than the clearance value, printing defects such as solder resist scattering are likely to occur, and if it is too small, the effect of the protrusion cannot be obtained.
Specifically, when a screen plate having a frame size of 320 to 450 mm square is used, the clearance value is generally 0.6 to 3.0 mm, and is adjusted as appropriate while checking the state of the printed matter. . Therefore, it is preferable to form the height of the protrusion in the range of 0.5 to 2.9 mm, and more preferably in the range of 0.5 to 2.5 mm.

The width A of the protruding portion is set according to the height of the protruding portion, is obtained as a calculated value W from the height H of the protruding portion by the following equation (1), and is set to a size that satisfies the condition of the equation (2). It is desirable. If the width is out of this range, it is difficult to obtain the effect of improving printability.
W = 20 · H ² −100 · H + 155 (1)
0.8W ≦ A ≦ 1.2W (2)
W: Width of protrusion [mm]
H: Height of protrusion [mm] (0.5 ≦ H ≦ 2.5)
Formula (1) is derived as an empirical formula based on many experiments.
Specifically, the width A of the protrusion is desirably formed in a range of 20 to 90 mm, and preferably in a range of 30 to 75 mm.

  Next, the protrusion is placed on a printing table of a screen printing machine and bonded with an adhesive. Although the kind of adhesive agent is not specifically limited, The thing with the high adhesive force which is effective with a small amount of application | coating is preferable. For example, the instantaneous strong adhesive Aron Alpha (registered trademark) manufactured by Toa Synthetic Chemical Co., Ltd., or Aron Alpha mixed with Aron Alpha-specific curing accelerator (aa setter 20) may be used. Primer treatment can also be performed as a pretreatment for the bonding step. In such a primer treatment, a primer solution, for example, Aron Polyprimer (a pretreatment agent for Aron Alpha) manufactured by Toa Synthetic Chemical Co., Ltd., a cyanone primer manufactured by High Pressure Gas Industry Co., Ltd., or the like can be used.

  When the protrusion is bonded to the printing table of the screen printing machine with an adhesive, the position (distance C) between the protrusion and the printing region is preferably 40 to 60 mm, and more preferably 40 to 50 mm. If it is shorter than 40 mm, solder resist splattering tends to occur at the printing edge, and if it is longer than 60 mm, it is difficult to obtain the effect of suppressing solder resist bleeding. Note that it is desirable to align the center positions in the length direction of the printing area and the protrusion.

  Next, a flexible printed wiring board is placed on the printing table, and a screen plate in which areas other than the solder resist coating portion are masked with an emulsion is brought into contact with a clearance of 0.5 mm or more. And the solder resist is printed through the screen plate.

The unit wiring pattern of the TCP or COF substrate is generally arranged in four rows of 35 mm width units or three rows of 48 mm width units on a long film having a width of 156 to 158 mm. The solder resist is printed at once in the range of ~ 144 mm × width 50 to 170 mm. When a screen plate having a frame size of 320 to 450 mm square is used, the clearance is set to 0.5 to 3.0 mm.
When screen printing is performed, the screen plate 8 is attached to the substrate surface of the wiring board, and ink is applied while pressing the screen plate 8 with the squeegee 7.
As a result, the same effect as when the clearance is locally increased in the printing area can be obtained, good printability can be ensured, and printing defects can be reduced even if the printing area is further enlarged in the TCP or COF substrate. It becomes possible.

(Embodiment 2)
In the first embodiment, the protrusion is formed on the upper surface of the printing table. However, the protrusion may be formed on the lower surface of the screen plate. The size of the protruding portion is the same as above, and when the protruding portion is bonded to the printing table of the screen printing machine with an adhesive, the distance C between the protruding portion and the printing area may be 40 to 60 mm as described above. desirable. Thereby, the effect similar to Embodiment 1 can be acquired.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. Note that the present invention is not limited to these without departing from the spirit of the present invention.

Example 1
A polypropylene resin plate was prepared, and a protrusion having a height of 2.5 mm, a width of 30 mm, and a length of 170 mm was produced. Next, this protrusion was attached to the upper surface of the printing table of the screen printing machine with an adhesive at a position where the protrusion was 60 mm on the front side of the printing area.
Using this screen printing machine, unit wiring patterns arranged in three rows with a width of 50 mm on a long film with a width of 160 mm are collectively packed in a range of 145 mm in length and 150 mm in width in a single printing operation. Printed. The clearance value between the printing table and the screen plate was 2.6 mm. This printing operation was repeated 30 times, but no solder resist splattering occurred and the occurrence of solder resist bleeding could be suppressed.

(Example 2)
The experiment was conducted in the same manner except that the protrusions were different from Example 1 in that the height was 0.5 mm, the width was 110 mm, and the length was 170 mm. The protrusion was attached to the upper surface of the printing table of the screen printing machine with an adhesive at a position where the protrusion was 60 mm on the front side of the printing area. Although the printing operation was repeated 30 times, no solder resist splattering occurred and the occurrence of solder resist bleeding could be suppressed.

(Example 3)
The same protrusion as in Example 2 was cut to a length of 100 mm, and the same experiment was performed using this. When the printing operation was repeated 30 times, a slight amount of solder resist scattering occurred, but there was no effect on the printing characteristics.

Example 4
The same protrusion as in Example 1 was used, and the protrusion was attached to the upper surface of the printing table of the screen printing machine with an adhesive at a position of 40 mm on the front side of the printing area.
Using this screen printer, as in Example 1, unit wiring patterns arranged in three rows in units of 50 mm width on a long film having a width of 160 mm were 145 mm long by 150 mm wide in a single printing operation. Solder resist was printed all over the area. This printing operation was repeated 30 times, but no solder resist splattering occurred and the occurrence of solder resist bleeding could be suppressed.

(Conventional example 1)
Without using the protrusions as described above, similarly to Example 1, unit wiring patterns arranged in three rows with a width of 50 mm on a long film with a width of 160 mm were 145 mm long by one printing operation. The solder resist was printed at once in the range of 150 mm in width. When this printing operation was repeated 5 times, the solder resist splattered, and thereafter, the solder resist bleed area was enlarged.

1 Protrusion 2 Printing table (squeegee sliding start side)
3 Printing table (squeegee sliding end side)
4 Flexible Printed Circuit Board 5 Print Area 6 Unit Circuit Area 7 Squeegee 8 Screen Plate 9 Solder Resist 10 Adsorption Holding Stage 11 Opening A Projection Width B Projection Length H Projection Height C Projection and Print Area Distance of

Claims (6)

In the method for manufacturing a flexible printed wiring board including a step of screen printing a solder resist on the flexible printed wiring board on which the wiring pattern is formed,
First, a plate-like protrusion having a height lower than the clearance value between the printing table and the screen plate is attached to a predetermined position on the upper surface of the printing table on the squeegee sliding start side or the lower surface of the screen plate, and then the printing table. Place the flexible printed circuit board on top and contact the screen plate with the area other than the solder resist coating part masked with emulsion with a clearance of 0.5mm or more, and then slide the squeegee. A method for producing a flexible printed wiring board, wherein a solder resist is printed through the screen plate.   The method for producing a flexible printed wiring board according to claim 1, wherein the flexible printed wiring board is a TCP (Tape Carrier Package) board or a COF (Chip On Film) board.   The method for manufacturing a flexible printed wiring board according to claim 1, wherein the height H of the protrusion is 0.5 to 2.5 mm. 2. The flexible print according to claim 1, wherein the width A of the protrusion is obtained as a calculated value W from the height H of the protrusion by the following formula (1) and satisfies the condition of the formula (2). A method for manufacturing a wiring board.
W = 20 · H ² −100 · H + 155 (1)
0.8W ≦ A ≦ 1.2W (2)   2. The method for manufacturing a flexible printed wiring board according to claim 1, wherein the length B of the protrusion is larger than the length of the solder resist coating region.   The method for manufacturing a flexible printed wiring board according to claim 1, wherein the protrusion is attached to the front side of the printing region at a distance C of 40 to 60 mm.

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