Manufacturing of printed circuit boards

Amateur radio technology for making printed circuit boards at home consists of several stages.

1. Preparation of PCB drawings.
2. Fiberglass preparation and drilling.
3. Drawing a picture.
4. Etching solution.
5. Etching.
6. Tinning.
7. Drawing with a laser printer.
8. Another way to apply a picture on a p / p using a laser printer.

Preparation of PCB drawings.

It is most convenient to manually make a drawing of a printed circuit board at 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 "copy the" school paper "into the box with a decrease of 2 times, in the most extreme case, you can use ordinary graph paper. The tracks on the soldering side should be drawn with solid lines, and the tracks on the part side (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 element legs are marked with dots around which you want to draw a soldering 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 a board "live" or 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 ruling pens approximately 1.5 mm. After the drawing is ready, you need to attach the drawing to the luminous surface (for example, window glass) with the back side to 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). you need to attach the drawing to the luminous surface (for example, window glass) with the back side to 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). you need to attach the drawing to the luminous surface (for example, window glass) with the back side to 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).

Fiberglass preparation and drilling.

Cut a piece of fiberglass to the size of the drawing. Remove burrs with a file. Place the blueprint on the board, fold the edges of the paper and secure them to the back with tape or (preferably) electrical tape. Next, the drilling process is carried out. Yes, right from the drawing and without punching. An important condition for the drill to not lead is its "freshness". However, what to expect from a specific drill, you can understand by drilling a test hole on some cut 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" the future holes. All holes, including mounting holes, are drilled with one (smallest) diameter. Next, you need to check the drilling for "clearance" as there are undoubtedly undrilled holes. Drill. After that, a drawing of the board is very carefully removed from the fiberglass (the danger is represented by burrs from drilling). Next, the fastening and other large-diameter holes are drilled.

After the operations performed, the surface of the board is cleaned with fine sandpaper. This process is necessary to remove drilling burrs and to better adhere the pattern paint to the surface. If possible, do not touch the smoothed surface with your fingers, so as not to leave grease marks. After stripping, it is necessary to degrease the board with alcohol (in extreme cases with acetone, but make sure that no white powdery stains remain). After that, you can only touch the end surfaces with your fingers.

Drawing a picture.

Of course, we argued a lot about the paint used and the technology for applying tracks in our circles, but I stopped at the one described below. Drawing is done with nitro paint, with rosin powder dissolved in it (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 reeders (which are very problematic to find nowadays). In addition, it is possible to use as a paint, asphalt-bitumen varnish, diluted to the required condition with xylene. The bottle will last for a very long time. It is possible to make the drawing pen yourself, with the appropriate training, of course. To do this, you can take a thin-walled glass tube and, stretching it on a flame (over a gas stove), break it in the middle. Then the broken tip "

Before you start drawing the paths of the printed circuit board, you need to draw the mounting pads for soldering the elements. They are applied using a glass reeler or a 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 caliper with a threaded distance lock (forgive me this expression, professional draftsmen, I never knew its real name), one of the needles of which is turned for a flat cutter). Further, the trimmed excess is cleaned with an awl or scalpel. In fact, I use a recycled school kit for these procedures. As a result, smooth round areas of the same diameter are obtained, which only need to be connected by paths, according to the previously drawn PCB drawing. Further, after drying, the second side is drawn. Then 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 a ruler (preferably metal), and then remove the excess by scratching. If you clean up the track right away, then depending on the degree of dryness of the paint, you can get "chips" even worse than the original ones. Check that the picture on the board matches the picture in the drawing. If you clean up the track right away, then depending on the degree of dryness of the paint, you can get "chips" even worse than the original ones. Check that the picture on the board matches the picture in the drawing. If you clean up the track right away, then depending on the degree of dryness of the paint, you can get "chips" even worse than the original ones. Check that the picture on the board matches the picture in the drawing.

Making an etching substance.

There are various compositions for etching, foil-clad material in the manufacture of printed circuit boards.

Recipe number 1.

For forced (within 4-6 min) etching, you can use the following composition (in parts by weight): 38% hydrochloric acid with a density of 1.19 g / cm ³ , 30% hydrogen peroxide (peroxide) — perhydrol. If hydrogen peroxide has a concentration of 16-18%, then 40 parts of peroxide and the same amount of water are taken for 20 parts by weight of acid. First, the peroxide is mixed with water, and then the acid is added. Printed conductors and contact pads should be protected with acid-resistant paint, for example, NTs-11 nitro-enamel.

Recipe number 2.

In a glass of cold water dissolve 4-6 tablets of hydrogen peroxide and carefully add 15-25 ml of concentrated sulfuric acid. BF-2 glue can be used to apply a printed circuit board pattern to foil-clad material. The etching time in this solution is approximately 1 hour.

Recipe number 3.

In 500 ml of hot (about 80 ° C) water, dissolve four tablespoons of table salt to two tablespoons of powdered copper sulfate. The solution becomes dark green in color. Ready to use immediately after cooling (optional with heat resistant paint, see above). The solution is enough to remove 200 cm ^{3 of} foil. Etching time is about 8 hours. If the pattern of the printed circuit board is made with a sufficiently heat-resistant paint or varnish, the temperature of the solution can be brought to about 50 ° C, and then the etching intensity will increase.

Recipe number 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 down, etching is started. Etching time 20-60 min. If you add 50 g of concentrated sulfuric acid to the solution, the etching will be more intense.

Recipe number 5.

In 200 ml of warm water, dissolve 150 g of ferric chloride in powder.

Ferric chloride preparation.

If there is no ready-made ferric chloride (in powder), then you can prepare it yourself. To do this, you must have 9% hydrochloric acid and fine iron filings. For 25 parts by volume of acid, take one part of iron filings. 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, and after 5-6 days the color changes to yellow-brown — ferric chloride solution is ready for use. For the preparation of ferric chloride, you can use powdered iron red lead. In this case, one volumetric part of concentrated hydrochloric acid requires 1.5-2 parts of red lead. The components are mixed in a glass container, adding red lead in small portions. After the termination of the chemical reaction, a precipitate and a solution of ferric chloride fall to the bottom. Ready to use

Etching and processing of the board.

Травление надо производить в пластмассовой (фото кювета) или фарфоровой (тарелка) посуде. Если плата небольших размеров, её удобно травить в тарелке. Глубокая тарелка выбирается так, чтобы плата не ложилась полностью на дно, а углами опиралась на стенки тарелки. Тогда между платой и дном будет пространство, заполненное раствором. Во время травления плату необходимо переворачивать и помешивать раствор. Если вам надо быстро протравить плату, подогрейте раствор до 50-70 градусов. Если плата больших размеров, то в крепёжные отверстия (по углам) вставьте спички так, чтобы они выступали на 5-10 мм с обеих сторон. Можно вставлять медную проволоку, но тогда будет большее насыщение раствора медью. Травите в фото кювете, помешивая и переворачивая плату. Работая с раствором хлорного железа необходимо соблюдать осторожность. Раствор практически невозможно смыть с одежды и предметов. При попадании на кожу, промойте содовым раствором. Фарфоровая тарелка легко отмывается от раствора и может применяться в дальнейшем по прямому назначению. По окончании травления слейте раствор в пластмассовую бутылку, он вам еще пригодится. Плату промойте в холодной проточной воде. Под тонкой струей воды снимите лак при помощи безопасного лезвия (счищать). Высушенную плату необходимо подчистить скальпелем от лишних соединений и расплывшегося лака. Если дорожки близко друг к другу, то можно расширить просвет скальпелем. После этого плата еще раз обрабатывается мелкой шкуркой.

Tinning the board.

You don't need to write about the usefulness of this procedure. Otherwise, you can stop at the previous one. Further, the surfaces of the board are covered with a brush with liquid rosin flux. Tinning is performed with a tinned screen braid (white) stripped of wires. Previously, the braid is impregnated with rosin and a small amount of solder (you can, of course, also alloy Rose, but this is already exotic). Further, the braid is pressed against the surface of the track with a soldering iron and slowly and evenly (selected experimentally) is carried out along the length of the track. If all the conditions are met correctly, the result will be a flat white tinned track. After all the tracks on all sides are processed, the board is rinsed with alcohol. Acetone rinsing is undesirable. since solder with acetone over time gives a conductive chemical compound in the form of a white coating on the edges of the pads and tracks, and with a sufficient installation density, there is a danger of unnecessary galvanic bonds. After flushing, holes are drilled (cleaned) for installing r / components.

The board is ready for installation.

Printed circuit boards using a laser printer.

The method of manufacturing single printed circuit boards with the transfer of a pattern from a printout to a laser printer is gaining more and more popularity among radio amateurs. It is best to print on thin coated paper - there is less nap in it, good results are obtained on the sheets of the Stereo & Video magazine, as well as self-adhesive substrates 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 on, contrast to maximum, etc.), and also use the path with the minimum paper bend (this option is available in older models of HP LJ 2 , LJ4, etc.). The board drawing must be "mirrored", this option is available in the print menu of many graphics programs, for example Corel Draw, Corel Photo Paint, and when printing from programs, those who do not know how to "mirror", it is necessary to use the output on Postscript printers, the option of mirroring for which is available in the driver. Instead of output to a laser printer, you can use photocopying, but also in the maximum contrast mode and on thermal paper from faxes. In the manufacture of two-layer printed circuit boards, to reduce the heat shrinkage of the paper, it is recommended to "run" the latter through the printer without printing an image before printing the image. In addition, both sides should be on the same sheet to avoid strong mismatch due to different shrinkage of the paper. The degreased board is placed with copper up on a flat surface, on top of the resulting print 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 the crepe de Chine (ask the ladies). The iron should not melt the laser-printed image immediately. That is, the toner at this temperature should turn from solid to viscous, but not liquid. When the board cools down, it must be immersed in warm water and held there for several minutes. As the paper becomes limp (it will be seen), everything will easily peel off, the rest can be simply rolled up with your finger. Instead of water, you can remove the paper with sulfuric acid. If the tracks are oiled, you have inadvertently 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 heating for too long. If the board is double-sided, then first, paper printouts of both sides are aligned to the light, two technological holes are punctured with a needle in any free opposite places, the first side of the board is "ironed" as usual, then it is drilled through the technological holes with a thin drill, and on the other side along them, to the light, it is combined with the paper printout of the other side. You can poison with ferric chloride (to speed up it a little), and a hodgepodge with hydroprite. All this was applied even on the getinax, there are no delamination of the tracks, tracks up to 0.8 mm wide are normally performed, and with some experience, up to 0.5 mm. After etching, the toner is removed with acetone, nail polish remover or Flux Off. Drilled, trimmed and so on, as usual ... Tracks up to 0.8 mm wide are normally performed, and with some experience, up to 0.5 mm. After etching, the toner is removed with acetone, nail polish remover or Flux Off. Drilled, trimmed and so on, as usual ... Tracks up to 0.8 mm wide are normally performed, and with some experience, up to 0.5 mm. After etching, the toner is removed with acetone, nail polish remover or Flux Off. Drilled, trimmed and so on, as usual ...

Another way to apply a picture on a p / p using a laser printer.

Making p / p using a laser printer and an iron is a rather tedious process, but it gives a pretty good result if you practice a little.

1 . Gently glue a sheet of fax paper (glossy side up) onto a sheet of plain paper (to compensate for the lack of hardness in faxing). What for? It is necessary to first drive the paper through the printer / laser oven - for shrinkage. For quiet dragging through the c / z path, it is enough to simply iron the thermal paper with an iron from the sensitive side.
2 . Paper - take a base from self-adhesive, or thermal paper for a fax is definitely thermal paper, and prepared - first, iron the sheets with a hot iron until they are flat (at the same time they will turn dark brown, then bluish-gray), fold them in this form for future use. Before removing the board, drive the sheet through the printer - for example, by printing a blank page. minimum sheet size - ~ 6 * 12 cm for HP 5 / 6L.
3... Print - at maximum fat content, mirrored. printing and transfer to a blank can be up to a week apart, I have not tried it again (this is for those who do not have a laser at home).
4 . Take the workpiece with a margin of 3-5 mm on each side. foil - lightly sand with a zero and wipe. there should not be any harmful deposits such as white sediment from denatured alcohol. I use isopropyl alcohol or gasoline "galosh" (aka "for lighters").
5 . Iron - with a normal, smooth surface. warm up in advance. Temperature - for waxing, you need to carefully select (I have a display meter for "isk.silk"), otherwise the impregnation will begin to transfer. for thermal paper - it can be higher.
6 . Dust and all sorts of little things - should not be, neither on foil, nor on paper.
7... To make a sandwich - on a flat thick plywood (though I have 3-millimeter paper) put a piece of thick cardboard, a blank board, blow off the dust, a drawing, for thermal paper (it's thin) - also a piece of moderately thick paper, a hot iron.
8 . You begin to crawl with the iron, pressing with a force of ~ 5..10 kg / sq. Dm. crawl about two minutes to grab.
9 . 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 to weld them. From time to time, you need to lower the iron to the entire plane so that the rest does not cool down. The thermal paper clearly shows the difference in welded and defective pieces.
ten... Well, you stroke for another minute to clear your conscience and remove the iron. The sandwich cools and the paper swells between the lanes. We do not wait for cooling, the board is immediately under a stream of steep boiling water.
11 . Now the board - under running water and a piece of wet foam rubber, you begin to wash the paper. It cannot be peeled off in large pieces or from dry foil. It is necessary to remove the wads of paper from the foam rubber more often. We take the paper by the corner and tear it off. Then remove the remnants with your 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 a lot of defects, or they are located in inconvenient places - see item 1, with variation of parameters.
13 . Glue the reverse side with strips of wide adhesive tape, poison. You can even in boiling FeCl3

Method of drawing a picture on a p / p using a laser printer

I make everything much simpler:
I take a blank and a simple Soviet eraser. I carefully wipe the entire board with an eraser. All oxidations are removed. You can also wipe it with gasoline just in case (but I don’t do it, it’s quite enough with an eraser). Then I take the thermal paper from the fax machine and iron it with an iron. It turns gray-violet. I insert this paper into the printer (I have HP 6L and I don’t glue any paper for rigidity, I haven’t chewed it yet) and mirror-print the board drawing. I put the paper on the p / p and start crawling with the iron. My power is 3/4 of the maximum power. I iron for 3-4 minutes. Then I throw the blank into hot-warm water and wait 5 minutes for the paper to turn sour. Then I roll the paper off the board with a sponge or fingers. Do not grip the edge of the paper or rip it off, the tracks may come off along with the paper! Just roll it off the board. Next - core, drill, cut and bait. And the board is ready.