|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING PCB manufacturing
Encyclopedia of radio electronics and electrical engineering / Ham Radio Technologies The amateur radio technology for manufacturing printed circuit boards at home consists of several stages.
Manually, it is most convenient to carry out a drawing of a printed circuit board on a scale of 1: 1 on paper from recorders (it has a cell with a side of 2.5 mm, in the “step” of microcircuits), if there is none, then you can “photocopy” school paper “in a box” with a decrease of 2 times, in the most extreme case, you can use the usual graph paper. The tracks on the soldering side should be drawn with solid lines, and the tracks on the side of the parts (in the case of double-sided mounting) should be drawn with dashed lines. It should be noted that the elements to be placed must be mirrored. The centers of the legs of the elements are marked with dots around which it is necessary to draw a solder pad. For subsequent actions, it is very important what size you choose the mounting pads for the elements (it's a shame when, when drawing the board "live", either the track between the pads does not pass, or after soldering, the elements fall out along with the pads). The width of the tracks should be chosen based on how you will draw the board, when using glass drawing pen of about 1.5 mm. After the drawing is ready, you need to attach the drawing to a luminous surface (for example, window glass) with the reverse side towards you and circle the dotted lines. So you get a drawing from the side of the installation of parts. Next, you need to cut out a drawing of a sheet of paper, but taking into account the "wings" for fasteners on each side (about 15 mm). Preparation of fiberglass and drilling Cut a piece of fiberglass to the size of the drawing. Remove burrs with a file. Overlay the drawing on the board, fold the edges of the paper and secure them to the back with tape or (preferably) electrical tape. The next step is the drilling process. Yes, right according to the drawing and without punching. An important condition for the drill not to lead is its "freshness". However, what to expect from a particular drill can be understood by drilling a test hole on some piece of fiberglass. The best solution to this problem is to have an appropriate drilling machine, even if it is homemade. If a "motor with a drill" is used, as a rule, it is better to "punch" future holes. All holes, including mounting holes, are drilled with one (smallest) diameter. Next, you need to check the drilling for "clearance" as there will definitely be undrilled holes. Drill. After that, the drawing of the board is very carefully removed from the fiberglass (the danger is burrs from drilling). Next, the fixing and other larger diameter holes are drilled. After the operations performed, the surface of the board is cleaned with a fine sandpaper. This process is necessary to remove burrs from drilling and for better adhesion of the paint pattern to the surface. If possible, do not touch the cleaned surface with your fingers so that grease marks do not remain. After stripping, it is necessary to degrease the board with alcohol (in extreme cases, with acetone, but make sure that white powdery stains do not remain). After that, you can only touch the end surfaces with your fingers. Of course, we argued a lot about the paint used and the technology for applying tracks in our circles, but I settled on the one described below. Drawing is done with nitro paint, with rosin powder dissolved in it (provides plasticity for some time after drying for correction and does not allow the paint to "lag behind" in case of etching with hot solutions). Drawing is done with glass drawing pen (which are very difficult to find nowadays). In addition, it is possible to use as a paint, asphalt-bitumen varnish, dissolved to the desired condition with xylene. The bottle will last a very long time. It is possible to make the drawers yourself, with appropriate training, of course. To do this, you can take a thin-walled glass tube and stretch it on a flame (over a gas stove) to break it in the middle. Then "finish" the broken tip on a fine sandpaper. Next, heating over the same flame, bend the tip to the desired angle. Difficult!? Actually no more than 5 minutes. You can also use disposable syringes for drawing. The varnish is drawn into a disposable syringe (1-2 ml) and a thin needle is placed. Before installation, the needle must be processed with a file, so that the edges are even (remove the sharp end). From the side of the piston, you can insert another needle to pass air into the syringe. Before you start drawing printed wiring tracks, you need to draw mounting pads for soldering elements. They are applied using a glass drawing pen or a sharply sharpened match around each hole, approximately 3 mm in diameter. Next, you need to let them dry. After that, you need to cut them with a compass to the desired diameter (I use a small measuring compass with a threaded distance lock (may the professional draftsmen forgive me for this expression, I never knew its real name), one of the needles of which is turned into a flat cutter). Next, the trimmed excess is cleaned with an awl or scalpel. In fact, I use recycled school cooking for these procedures. As a result, smooth round areas of the same diameter are obtained, which can only be connected by tracks, according to the previously drawn drawing of the printed circuit board. Further, after drying, the second side is drawn. After that, the tracks and errors are corrected with a scalpel. Moreover, it should be noted that in order to align the edge of the track, you must first cut the edge along the ruler (preferably metal), and then remove the excess by scratching. If you clean the track right away, then, depending on the degree of overdrying of the paint, you can get "chips" even worse than the original ones. Check that the pattern on the board matches the pattern on the drawing. There are various compositions for etching, foil material in the manufacture of printed circuit boards. Recipe №1.For forced (within 4-6 min) etching, you can use the following composition (in mass parts): 38% hydrochloric acid with a density of 1,19 g/cm3, 30% hydrogen peroxide-perhydrol. If hydrogen peroxide has a concentration of 16-18%, then 20 parts of peroxide and the same amount of water are taken for 40 mass parts of acid. First, peroxide is mixed with water, and then acid is added. Printed conductors and pads should be protected with acid-resistant paint, for example, NTs-11 nitro enamel. Recipe №2.Dissolve 4-6 tablets of hydrogen peroxide in a glass of cold water and carefully add 15-25 ml of concentrated sulfuric acid. To apply a printed circuit board pattern on a foil material, you can use BF-2 glue. The etching time in this solution is approximately 1 hour. Recipe №3.In 500 ml of hot (about 80 ° C) water, dissolve four tablespoons of table salt to two tablespoons of copper sulfate crushed into powder. The solution becomes dark green in color. Ready for use immediately after cooling (with heat-resistant paint, see above, optional). The solution is enough to remove 200 cm3 foil. The etching time is about 8 hours. If the printed circuit board pattern is made with sufficiently heat-resistant paint or varnish, the temperature of the solution can be brought up to about 50 ° C, and then the etching intensity will increase. Recipe №4.Dissolve 350 g of chromic anhydride in 1 liter of hot water (60-70 °C), then add 50 g of sodium chloride *. After the solution has cooled, start pickling. Etching time 20-60 min. If 50 g of concentrated sulfuric acid is added to the solution, then the etching will be more intense. Recipe №5.Dissolve 200 g of ferric chloride powder in 150 ml of warm water. Preparation of ferric chloride If there is no ferric chloride in finished form (in powder), then you can cook it yourself. To do this, you must have 9% hydrochloric acid and fine iron filings. For 25 parts by volume of acid, one part of iron filings is taken. Sawdust is poured into an open vessel with acid and left for several days. At the end of the reaction, the solution becomes light green in color, and after 5-6 days the color changes to yellow-brown - the solution of ferric chloride is ready for use. For the preparation of ferric chloride, you can use powdered iron minium. At the same time, 1,5-2 parts of red lead are required for one volume part of concentrated hydrochloric acid. The components are mixed in a glass dish, adding red lead in small portions. After the cessation of the chemical reaction, a precipitate and a solution of ferric chloride fall to the bottom. Ready to use Etching should be done in plastic (photo cuvette) or porcelain (plate) dishes. If the board is small, it is convenient to pickle it in a plate. A deep plate is chosen so that the board does not lie completely on the bottom, but rests at the corners on the walls of the plate. Then between the board and the bottom there will be a space filled with a solution. During etching, the board must be turned over and the solution stirred. If you need to quickly pickle the board, heat the solution to 50-70 degrees. If the board is large, then insert matches into the mounting holes (at the corners) so that they protrude 5-10 mm on both sides. You can insert a copper wire, but then there will be a greater saturation of the solution with copper. Etch in a photo cuvette, stirring and turning the board over. When working with a solution of ferric chloride, care must be taken. The solution is almost impossible to wash off clothes and objects. In case of contact with skin, wash with saline solution. The porcelain plate is easily washed from the solution and can be used in the future for its intended purpose. After etching, pour the solution into a plastic bottle, you will still need it. Rinse the board in cold running water. Under a thin stream of water, remove the varnish with a safety blade (scrape off). The dried board must be cleaned with a scalpel from unnecessary connections and blurred varnish. If the paths are close to each other, then you can expand the lumen with a scalpel. After that, the board is again processed with fine sandpaper. You can not write about the usefulness of this procedure. Otherwise, you can stop at the previous one. Next, the board surfaces are covered with a brush with liquid rosin flux. Tinning is done with wire-free tinned screen braid (white). Previously, the braid is impregnated with rosin and a small amount of solder (you can, of course, also use Rosé alloy, but this is already exotic). Next, the braid is pressed against the surface of the track with a soldering iron and slowly evenly (selected experimentally) is carried out along the length of the track. If all conditions are met correctly, then as a result you will get a smooth white tinned track. After all the tracks on all sides are processed, the board is flushed with alcohol. Washing with acetone is undesirable, since the solder with acetone gives over time a conductive chemical compound in the form of a white coating along the edges of the pads and tracks, and with sufficient mounting density there is a danger of unnecessary galvanic connections. After washing, drilling (cleaning) of holes for the installation of r / components is carried out. The board is ready for installation. Printed circuit boards with laser printer Increasingly popular among radio amateurs is the method of manufacturing single printed circuit boards with the transfer of a pattern from a printout on a laser printer. It is best to print on thin coated paper - it has less pile, a good result is obtained on the sheets of the magazine "Stereo & Video", as well as the substrates of "self-adhesives" and thermal paper for faxes (choose the side experimentally). In laser printers, turn on the maximum toner supply mode (turn off the "economy" mode if it was turned on, turn the contrast to the maximum, etc.), and also use the paper path with minimal paper curl (this option is available in older HP LJ 2 models , LJ4, etc.). The board drawing must be "mirrored", this option is available in the print menu of many graphics programs, such as Corel Draw, Corel Photo Paint, and when printing from programs that cannot "mirror", you must apply output to Postscript printers that have the mirroring option. in the driver. Instead of output on a laser printer, photocopying can be used, but also in maximum contrast mode and on thermal paper from faxes. In the manufacture of two-layer printed circuit boards, in order to reduce the heat shrinkage of the paper, it is recommended to "run" the paper through the printer empty before printing the image (without printing a picture). In addition, both sides must be on the same sheet to avoid strong misalignment due to different heat shrinkage of the paper. The degreased board lays down with copper up on a flat surface, from above the imprint obtained with toner down. This "sandwich" is pressed from the side of the paper with an iron (for 20 - 30 seconds), heated to the temperature of ironing crepe de chine (ask the ladies). The iron must not melt the image made by the laser printer immediately. That is, the toner at this temperature should become viscous from solid, but not liquid. When the board has cooled down, it must be lowered into warm water, held there for several minutes. As the paper sags (it will be visible), everything will be easily torn off, the rest is just rolled up with your finger. Instead of water, paper can be removed with sulfuric acid. If the tracks are lubricated, you carelessly removed the iron or put on a cold load. If the tracks are missing somewhere, the iron is too cold. If the tracks become wide, the iron is too hot, or the board has been heated for too long. If the board is double-sided, then first the paper printouts of both sides are combined through the light, two technological holes are pierced with a needle in any free opposite places, the first side of the board is “ironed” as usual, then it is drilled along the technological holes with a thin drill, and on the other side along them on the gap is aligned with the paper printout of the other side. You can poison with ferric chloride (to speed up a little heat), and hodgepodge with hydropyrite. All this was used even on getinaks, there are no delaminations of the tracks, tracks up to 0,8 mm wide are normally performed, and with some experience up to 0,5 mm. Once etched, the toner is removed with acetone, nail polish remover, or Flux Off spray. Drilled, cut and so on, as usual... Another way to apply a pattern on a payment order using a laser printer. Making p / p using a laser printer and an iron is a rather tedious process, but gives a pretty good result with a little practice. 1. Gently glue a sheet of fax paper (glossy side up) onto a sheet of plain paper (to compensate for the lack of faxing rigidity). What for? It is necessary to pre-drive the paper through the printer / laser oven - for shrinkage. For a quiet pulling through the duct, it is enough to simply iron the thermal paper with an iron from the sensitive side. 2. Paper - take the base from self-adhesive, or thermal paper for faxing, definitely thermal paper, and prepared - first iron the sheets with a hot iron to a flat state (they will turn dark brown, then bluish-gray), fold them in this form for future use. before outputting the board, run the sheet through the printer - for example, by printing a blank page. the minimum sheet size is ~6*12 cm for HP 5/6L. 3. Print - at the maximum fat content, mirrored. printing and transfer to a blank can be up to a week apart, I haven’t tried it again (this is for those who don’t have a laser at home). 4. Take the workpiece with a margin of 3-5 mm on each side. foil - lightly sand with zero and wipe. there should not be any harmful deposits such as a white precipitate from denatured alcohol. I use isopropyl alcohol or gas "galosh" (aka "for lighters"). 5. Iron - with a normal, smooth surface. warm up in advance. Temperature - for waxing it is necessary to select more carefully (I have a display meter for "isk.silk"), otherwise the impregnation will begin to be transferred. for thermal paper - can be higher. 6. Dust and any trifles - should not be, neither on foil, nor on paper. 7. Make a sandwich - put a piece of thick cardboard, a board blank, blow off dust, a drawing, for thermal paper (it’s thin) - also a piece of moderately thick paper, a hot iron. 8. You start to crawl with an iron, pressing with a force of ~ 5..10 kg / sq. dm. crawl for two minutes to catch it. 9. By tilting the iron very slightly, you roll individual tracks for a couple of minutes. It is very important here not to crush the tracks, and at the same time weld them. From time to time it is necessary to lower the iron to the entire plane so that the rest does not cool down. Thermal paper clearly shows the difference in welded and defective pieces. 10. Well, you iron for another minute to clear your conscience and remove the iron. The sandwich cools down and sections of paper swell between the tracks. We do not wait for cooling, the board is immediately under a stream of boiling water. 11. Now the board - under a stream of water and a piece of wet foam rubber, you begin to erase the paper. It cannot be torn off in large pieces or from dry foil. It is necessary to remove clumps of paper from the foam rubber more often. We take the paper by the corner and tear it off. Then we remove the remnants with a finger / rag / foam rubber. 12. With a new piece of sponge you erase the pile (as far as possible), you look at the wet drawing under a magnifying glass. if there are many defects, or they are located in inconvenient places - see item 1, with a variation of the parameters. 13. Seal the reverse side with strips of wide adhesive tape, we poison. It is possible even in boiling FeCl3 Publication: cxem.net
Artificial leather for touch emulation
15.04.2024 Petgugu Global cat litter
15.04.2024 The attractiveness of caring men
14.04.2024
▪ Cable Power Specification for HDMI Cables ▪ Predicting major solar flares
▪ section of the site Labor protection. Selection of articles ▪ article Money, credit, banks. Crib ▪ Article How do we talk? Detailed answer ▪ article Rosichka creeping. Legends, cultivation, methods of application ▪ MARSHALL tube preamplifier. Encyclopedia of radio electronics and electrical engineering
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page