TW201309142A - Solder-resist printing method for flexible printed circuit board - Google Patents

Abstract

This invention relates to a solder-resist printing method for a flexible printed circuit board, comprising: providing a wiring line-containing flexible printed circuit board manufacture on a printing machine platform; performing a steel screen printing process to squeeze the solder-resist ink through the hollow portion on the steel plate and fill the ink in the gaps between the wiring lines, wherein the hollow property of the hollow portion enables the solder-resist ink to completely fill the gaps to enhance the controllability of the printed shape; then performing a silk screen printing process to control the thickness of the solder-resist layer and the surface flatness of the manufacture; and then performing shaping processes including pre-baking, exposure, development and continuous baking. In this invention, steel screen printing is employed to fill the gaps completely with solder-resist ink, and silk screen printing is employed to ensure flat and smooth surface of the solder-resist layer. Therefore, the surface smoothness can meet user's demand, and the problem of copper leakage from orifice rings can be inhibited, thereby increasing the product yield.

Description

Anti-weld printing method for flexible printed circuit board

The invention relates to a solder resist printing method for a flexible printed circuit board, in particular to a solder resist printing method for a flexible printed circuit board capable of reducing copper leakage of a hole ring and improving yield.

After the circuit board is completed, the soldering layer is further coated on the circuit to protect the circuit. The soldering layer is applied by screen printing. As shown in Figure 2, the flexible printed circuit board 90 is placed. On the printing machine table 93, a screen plate 94 is disposed at a distance from the printing machine table 93. The screen plate 94 has a frame 95. The frame 95 is provided with a wire cloth 96 having a proximity printing. a first side of the machine table 93 and a second side opposite the first side, a mesh extending through the first side and the second side is formed at the predetermined coating area, and a scraper 97 is disposed adjacent to the second side And a supply member 98 for providing solder resist ink, the solder resist ink flowing out from the supply member 98 to the second side of the screen cloth 96, and the solder resist ink is printed on the flexible printed circuit board 90 through the through mesh through the doctor blade 97. A solder resist layer 92 is formed.

At present, the screen printing operation method is to increase the size of the solder mask ink cover and increase the number of screen printing. Please refer to the cover hole printing process shown in Figure 3 for the first screen printing, pre-baking, exposure, development, short baking. After pickling, the solder resist ink 80a is filled into the opening 99a between the lines 91a of the flexible printed circuit board 90a to form an ink cover hole, followed by a second screen printing, pre-baking ^, exposure, development, and long baking on the line. A solder resist layer 92a is formed on 91a.

Referring to the multiple printing process of the solder resist ink shown in FIG. 4, the scraper 97 repeats the multiple scraping operation, so that the solder resist ink 80b enters the gap 99b between the lines 91b and covers the line 91b, and then pre-bakes and exposes. , development, long baking, forming a solder resist layer 92b outside the line 91b.

Among them, the whole process adopts screen printing, and the screen cloth 96 is deformed by the pressing of the scraper 97, so the control of the printing shape is not good, and the welding-proof ink cover hole operation is added, in addition to the laborious and time-consuming cost, the solder resist layer is formed. The surface of 92a is uneven, resulting in ink bulging, resulting in poor copper leakage (golden eye) in the hole ring. In addition, the number of screen printing soldering inks is increased, and the pores 99b between the lines 91b cannot be effectively filled, which still causes the hole ring to leak. Bad copper.

The main object of the present invention is to provide a solder resist printing method for a flexible printed circuit board, which is designed to improve the current solder mask layer by screen printing operation, and can not effectively reduce the surface defect and the defect rate of the hole ring leakage copper. Problems, as well as screen printing jobs, have problems with poor shape control.

In order to achieve the foregoing object, a solder resist printing method for a flexible printed circuit board designed by the present invention comprises: providing a flexible printed circuit board with a printed circuit board on a printing machine table; and performing a stencil printing device of the printing machine In the stencil printing operation, the steel sheet of the stencil printing device forms a transparent portion at a predetermined printing position, and the steel sheet is placed on the product, and the welding ink is scraped by the matching scraper to make the solder resist ink pass through the steel sheet. The part is squeezed to fill the gap between the lines; the screen printing operation is performed by the screen printing device of the printing machine, and the through-hole is formed on the screen cloth of the screen printing device, and the matching blade can scrape the solder resist ink. The hole is coated on the product to form a solder resist layer, and the screen printing operation controls the thickness of the solder resist layer and the surface flatness; and the setting operation, the pre-baking, exposing, developing and long baking steps are performed to shape the solder resist layer .

Wherein, the solder resist printing method of the flexible printed circuit board of the present invention adopts a stencil printing operation, and the solder resist ink is indeed squeezed and filled into the pore by the scraper of the steel sheet, and then the thickness of the solder resist layer is controlled by screen printing. With the flatness of the surface, the surface of the solder resist layer is kept flat to meet the needs of users, and the occurrence of defective copper leakage of the ring ring can be reduced, and the product yield can be improved.

Referring to FIG. 1A, the solder resist printing method of the flexible printed circuit board of the present invention provides a product 10 on a printing machine table 14, which is a flexible printed circuit board 11 on which the wiring 12 has been laid, and then uses a steel mesh of the printing machine. The printing apparatus performs a stencil printing operation, and the stencil printing apparatus has a frame 15 and a steel sheet 16, the steel sheet 16 is located in the frame 15, and the steel sheet 16 forms a transparent portion 17 at a predetermined printing position. When the stencil printing operation is performed, the steel sheet 16 is placed on the product 10, further adjacent to the surface of the product 10, and the apertures 13 between the lines 12 are matched with the transparent portion 17 of the steel sheet 16, and then printed with steel mesh. The doctor blade 18 scrapes the solder resist ink 19, and the solder resist ink 19 is pressed through the transparent portion 17 of the steel sheet 16, thereby reliably filling the voids 13 between the lines 12.

Referring to FIG. 1B, the screen printing operation of the product 10 subjected to the stencil printing operation is performed by a screen printing device of a printing machine, wherein the screen cloth 20 of the screen printing device is formed with a solder resist ink. The through-hole 19 passes through the scraper 21 matched by the screen printing device, and the solder resist ink 19 is scraped out of the through hole and coated on the product 10 to form a solder resist layer 30 covering the line 12, and the screen printing operation can be performed. The thickness of the solder resist layer 30 is controlled and the flatness of the surface of the solder resist layer 30 is adjusted.

After the product 10 has printed the solder resist layer 30, it enters the pre-baking, exposure, development and long-baking sizing operation steps to shape the solder resist layer 30.

In the preferred embodiment of the invention, the optimum offset tolerance of the steel sheet 16 in the stencil printing operation is 0.3 mm, avoiding the offset and failing to fill the voids 13.

In summary, the solder resist printing method of the flexible printed circuit board of the present invention first performs stencil printing on the product 10, and the transparent portion 17 provided by the steel sheet 16 allows the scraper 18 to surely squeeze the solder resist ink 19 into the pores. 13, and can improve the controllability of the printing shape, and then adjust the thickness of the solder resist layer 30 by screen printing, and keep the surface of the solder resist layer 30 flat, reduce the generation of copper leakage of the hole ring, and effectively improve the product yield, phase The solder resist printing method of the flexible printed circuit board of the invention is more time-saving and labor-saving, and the cost is lower than that of the conventional solder-proof printing method which is screen-printed once and then screen-printed once and fixed. The solder resist printing method of the number of screen printing times, the solder resist printing method of the flexible printed circuit board of the present invention can improve the integrity of the fill-in void 13 of the solder resist ink 19, so that the yield can be effectively improved.

10. . . product

11. . . Flexible printed circuit board

12. . . line

13. . . Porosity

14. . . Press table

15. . . Frame

16. . . Steel sheet

17. . . Ventilation

18. . . scraper

19. . . Solder mask ink

20. . . Wire mesh

twenty one. . . scraper

30. . . Solder mask

80a, 80b. . . Solder mask ink

90, 90a. . . Flexible printed circuit board

91a, 91b. . . line

92, 92a, 92b. . . Solder mask

93. . . Press table

94. . . Screen version

95. . . frame

96. . . Wire mesh

97. . . scraper

98. . . Supply

99a, 99b. . . Porosity

1A is a side elevational view showing a preferred embodiment of stencil printing of the solder resist printing method of the flexible printed circuit board of the present invention.

Fig. 1B is a side elevational view showing a preferred embodiment of screen printing of the solder resist printing method of the flexible printed circuit board of the present invention.

Figure 2 is a side elevational view of a preferred embodiment of screen printing for a conventional solder resist printing method.

Fig. 3 is a flow chart showing a preferred embodiment of an additional solder mask ink cover hole for a conventional solder resist printing method.

Figure 4 is a flow diagram showing a preferred embodiment of one of the increased number of screen printing times for conventional solder mask printing methods.

10. . . product

11. . . Flexible printed circuit board

12. . . line

13. . . Porosity

14. . . Press table

15. . . Frame

16. . . Steel sheet

17. . . Ventilation

18. . . scraper

19. . . Solder mask ink

Claims (3)

A solder resist printing method for a flexible printed circuit board, comprising: providing a flexible printed circuit board product of a wiring line on a printing machine table; stencil printing operation by a stencil printing device of a printing machine, and a stencil printing device The steel sheet forms a transparent portion at a predetermined printing position, and the steel sheet is placed on the product, and the solder resist ink is scraped by the matching scraper, so that the solder resist ink is pressed through the transparent portion of the steel sheet to fill the gap between the lines. Pore; screen printing operation by a screen printing device of a printing machine; a through-hole is formed on the screen cloth of the screen printing device, and the matching blade can scrape the soldering ink out of the through hole and apply it on the product to form an anti-adhesion The solder layer controls the thickness and surface smoothness of the solder mask by screen printing; and the shaping operation, the pre-baking, exposure, development and long-bake steps are used to shape the solder resist layer. The anti-weld printing method of the flexible printed circuit board according to the first aspect of the invention, wherein in the stencil printing operation, the surface of the steel sheet adjacent to the product and the pores between the lines fall on the transparent portion of the steel sheet, The solder resist ink can be filled with pores. A solder resist printing method for a flexible printed circuit board according to claim 1 or 2, wherein the optimum offset tolerance of the steel sheet in the stencil printing operation is 0.3 mm.