FPC in the production process in resistance welding process.

FPC printing plate drying resistance welding process, the net India has printed circuit board solder. Photographic negatives will be printed board welding disc so that the cover in the exposure from UV irradiation and block welding protective layer after UV irradiation is more robust attachment on the printed circuit board, pad has not been UV irradiation, exposing the copper pads can, so that the hot air leveling of lead and tin.
The drying process can be divided into three operating procedures:
The first procedure is exposure.
First, before the start of exposure to check the exposure box of polyester film and glass box is clean, if not clean should promptly with anti-static cloth to wipe clean. Then, open exposure machine power switch, then open the vacuum button select exposure program, shake the shutter, before yet to begin formal exposure, should let machine "exposure" five times exposure, exposure is enables the machine to enter a state of saturation of the work, the most important is the UV exposure light energy into the normal range. If the energy of the exposure light is not "empty", it may not be in the best working condition. In the exposure will make the problem of printed boards. "Exposure" five times, exposure machine has entered the best working condition, using photoplate para previous, to check the quality of the slab is qualified. Check slab irrigation membrane surface whether pinhole and exposure, and printed board graphics are the same, because this will check the photographic negatives can avoid because of some unnecessary reasons make PCB rework or scrap.
Sun resistance welding usually use visual positioning, using silver bottom slab, the alignment of bottom slab of pad and PCB pads Kong Zhonghe. Can be fixed with adhesive tape for exposure. At the para position in the face of sun resistance welding is usually used visual positioning, using silver bottom slab, the alignment of the bottom slab of pad and PCB pad holes are overlapped, can be fixed with adhesive tape for exposure. At the para position in the face of a lot, for example, because the bottom slab and the temperature, humidity and other factors, if the temperature and humidity control, photoplate may shrink or enlarge the deformation, so bask in the solder, photoplate and printed board pad not completely anastomosis. In narrow bottom slab, see bottom slab pad and PCB pads differ much, if the difference is small can in hot air leveling of lead and tin, then there is no big problem selenium resistance welding can be carried out. If the difference is very big, only to try to make a replica of the pad plate coincide. At the para position before, should also pay attention to bottom slab of membrane surface is anti, should ensure that the membrane surface in the para position towards, if toward the membrane surface is scratched, resulting in bottom slab of exposure, the drying out of the printed board without exposure resistance solder, a serious cause of printed circuit board scrap. In addition, but also pay attention to the sometimes imposition of bottom slab and printed graphics boards do not coincide, usually imposition bottom slab along the spell on the edge of the board cut open, then to fight a single alignment, the printed circuit board of after exposure. The above problems are the problems that should be paid attention to in the formal exposure of selenium.
Then, the solder resist welding, before the exposure should check whether the printed board is vacuum box cover. The pressure of the vacuum suction should be enough to exist. If gas dew will make the ultraviolet along the side of the board shines into the graphics, resulting in exposure of shade, developing away, sometimes encountered in single exposure, in this case, the single non graphical side with ultraviolet light emitted by the black cloth and exposure lamp separated, if it's not black, UV through no graphic side transmission to the welding pad makes the welding hole plate resistance solder after exposure, a developer can not afford. In the exposure on both sides of the graph is not consistent with the printed circuit board, the first screen printing side resistance welding and single side exposure, developing, in the screen printing on the other side of the resistance welding, because if both sides of screen printing exposure, a complex graphics pad more and need to shading part, while the other side need less shading part, make the ultraviolet through a irradiation to on the other side, shading side after UV irradiation, in developing sensible not to drop shadow, will cause rework or scrap. In exposure process, will encounter network printing printed circuit board in the curing time is not drying. In this case, para will enable resistance solder touches the photoplate and printed circuit board to rework, so do not found, especially most of the printed circuit board is not drying will be placed in an oven to drying. These conditions are easy to appear in the process of the problem, so we should seriously check, timely detection, timely solution.

The second procedure is to develop.
Development operations in general to be carried out in the development machine, control the temperature of the developer, transfer speed, spray pressure and other development parameters, can get a better development effect. Development is to remove the part of the shading with the developer solution to remove the solder mask on the solder pad. The solution for development is one percent anhydrous sodium carbonate, and the liquid temperature is usually between thirty and thirty-five degrees Celsius. Before the formal development, the developer should be heated up, so that the solution reaches a predetermined temperature, so as to achieve the best development effect. Development machine is divided into three parts: the first section is the spray section, mainly by the use of high pressure jet anhydrous sodium carbonate, so that the resistance of the solder is not exposed to dissolve;
The second paragraph is washing section, the first is the washing of the high-pressure pump and the residue washed clean solution, and then into the washing water circulation and thoroughly washed. The third paragraph is dry, dry period before and after each have a wind knife drying of the board with hot air, another dry section of high temperature can also be the board drying. By showing points to determine the correct development time, show the point must be maintained at a constant percentage of the developing a total length of. If the show from the outlet of the development section too close, the unexposed solder layer not sufficient development will cause unexposed solder layer of residual may stay on the surface, if show point away from the entrance to the developing section too close, was exposed to the solder layer due to contact with developer long ask may by erosion and become scared, lose luster. Usually show control point in developing a total length of 40% - 60%. In addition, we must pay attention to in the developing, it is easy to scratch board, is solved by the usual method is during development, put the board operator should wear gloves, on board to gently, and is printed board sizes, so as much as possible about the size of a large together, in the board, between the board and the board to keep a certain distance, to prevent transmission, the board crowded, "card" phenomenon. Show end film, the printed board placed in wooden bracket.
The following is a third operation procedure:
Repair plate includes two aspects, one is the defects of image inpainting, second is removal of defects and the requirement of image independent. In the process of amending the board should pay attention to yarn gloves, to anti hand sweat pollution of plate surface, a common surface defects:
1, also known as skip feibai.
Is mainly due to the large current electroplating, coating thickness, resulting in high line graph, in the screen printing of PCB, the scraper knife and screen printing frame into a certain angle screen printing, so in both sides of the line due to the high line, ink: cause printing jump. Another reason is scraper knife has a gap, gap not ink, printing jump, the solution method causes are mainly control the plating current and check the scraper knife if there are gaps.
2, oxidation.
Printed board solder layer copper lines on a black signs, causes a wiping plate water without drying, printing solder printing plate surface is liquid is spilled or with fingerprint, the solving method is screen printing visual inspection of printed board on both sides of the copper foil whether oxidative phenomenon.
3, the surface is not uniform.
In the screen printing did not pay attention to timely printing paper, clear the screen of the residual ink, resulting in uneven surface, the solution is to timely printing paper clear the screen of residual ink.
4, hole in resistance welding.
Caused by the reason is in the screen printing not timely printing paper, causing screen accumulation too much residual ink, under the squeegee pressure to residual ink printed into the hole, solution is timely printing paper, and screen mesh size is too low, also can cause the hole in the solder, to use high mesh screen version of the business, ink viscosity is too low, change the viscosity of the ink, scraper screen printing angle, the appropriate adjustment angle of scraper network printing, a scraper blade turned round, sharpening the scraper blade.
5, graphics have a pinhole.
The reason is that the photoplate on dirt, so that the printed circuit board in the exposure process should see a portion of the light and did not see the light, resulting in graphic pinhole, solution is in the exposure process often check the cleanliness of the photographic film.
6, the surface of dirt.
Because the printed plate screen printing is belongs to the clean room, so in screen printing pumping outlet should be a piece of static line to play the role of adsorption in the air in the hair and other debris, so in order to reduce the surface dirt, fully guarantee the clean room cleanliness and proper implementation of some specific measures, such as entering the clean room to fully guarantee the operator of clean degree, to avoid irrelevant personnel through clean room, regular cleaning clean room.
7, the two sides of the color is not consistent.
Caused by reasons, may be the difference of screen printing on both sides of the knife for a few large, there is the mixture of old and new ink, may side with a good mix of New Mexico, while the other side is by placing a long time old ink, solution is to try and avoid the emergence of the above two kinds of circumstances.
8, cracking.
Due to the exposure, exposure is not enough, resulting in surface with small flaws, the solution is measured exposure the exposure light energy, exposure time and other parameters comprehensive value between reach 9-11 level exposure series, within the scope of this won't crack.

9, bubbles.
PCB line or single line side, after developing the air bubble. The main reason: two or more lines between bubbles is mainly due to the line spacing is too narrow and the line is too high, the resistance of screen printing solder cannot be printed onto a substrate, resulting in the presence of air or moisture resistance between solder and substrate, in curing and exposure gas thermal expansion caused by single lines is mainly due to excessive lines. The high line and line contact in scraper, scraper, and lines between the angle increases, the resistance of the solder lines cannot be printed to make root, the presence of gas lines and solder layer between the lateral roots, heated air bubbles, the solution is: screen printing should inspection screen printing material is completely printed onto a substrate and the line side wall, strict control of current electroplating.
10, heavy shadow:
The printed board pad next to a regular ink point exists, the reason is screen printing when the printed circuit board positioning and not in prison and screen residue no time to remove the accumulated to a printed circuit board, the solution is positioning pin is used for firmly fixed and timely printing paper to remove residual ink on the screen.
In the process of amending the version, due to some defects in the printing is very serious is not repaired, with aqueous solution of sodium hydroxide heating the original resistance solder dissolved away, then re printing net exposure to rework, if printed in small defects, such as small dew copper can be with a fine brush stained with a good tune resistance solder carefully repaired.
Above, is printed in all of C's process, although the process on a printed circuit board of the procedures is a relatively simple procedure. However, it also has a important role, sun resistance welding process control printing plate appearance and inner hole and printed board "beautiful coat" do "the most beautiful" to the printed board looks more comfortable, and protective effect, control the hole quality, so the printed plate hole there will be no resistance solder, ensure the quality of printed circuit board, so to say, printed circuit board drying resistance welding process is very important process.

from AKEN ZHANG,printed circuit boards including fpc flexible circuit boards fabrication in china.