Jet-diffusion method for the manufacture of printed circuit boards. Direct inkjet printing of a printed circuit board template Converting a printer to burn circuit boards

From time to time, I sometimes need to make printed circuit boards for my crafts. LUT is an extremely capricious method for me - either the toner will melt and spread, then the quality of the paper will not work, then some other hemorrhoids - steel-iron nerves are needed. For photoresist, specific reagents and a laminator.

“And if we build a special machine for this? To immediately print with paint? ”, - I thought. “Remake the printer!”, laziness remarked reasonably. A search on the Internet revealed that people successfully remake inkjet printers for printing on textolite, but this is a rather laborious process (you need to finish and raise the frame with the print head, etc.), moreover, I value my inkjet printer like Madame Gritsatsueva sifter (MFP, after all). But I had an unnecessary laser HP lj 6L lying around idle - in general, I was lying around. It was useful to look at the characteristics and accidentally stumbled upon (the cache of the article, for every fireman) on the alteration of this particular printer for textolite. But the topic in the article was not fully revealed - in particular, it does not tell how to make the toner stick to the textolite foil, how to bake this toner later and, most importantly, there is no video demonstration of a working sample, so I brought this matter to mind on your own. I strongly recommend that you read the above article, because I will not repeat what is described there in detail - there is nothing to copy-paste. There are many photos under the cut.

So, the alteration itself lies in the little things - make a cut in the back wall, remove the baffle plate and the stove (so that the printed pattern is not smeared). The stove temperature sensor must be replaced with a resistor with a resistance of 8.2 kOhm. I recommend doing it like this (simply short-circuit the temperature sensor with a resistor so as not to fiddle with fixing it):

Nothing needs to be done with the connector that supplies the heating voltage. Unplug the stove and that's it.

Next, you need to work with the impact pad - this is what was behind the paper pickup roller - you need to cut it off, leaving only the sides. I'm sorry, but there is no photo with the back part not sawn off - I forgot to take a picture, and when I came to my senses and came to my senses, everything had already been sawn off. I don't know how it happened. Nightmare.

This is how it should look like:

Yes, I almost forgot: be careful with the paper passage sensor (it is, rather, the upper arm of its damper, is located over there to the left of the paper pickup roller) - do not accidentally cut off its fasteners, otherwise the printer will not be able to control the end of the sheet in the feed path.

The simplest, most affordable and most effective way of making printed circuit boards at home is the so-called "laser-iron" (or LUT). The description of this method can be easily found by the corresponding keywords, so we will not dwell on it in detail, we only note that in the simplest version, all that is needed is access to a laser printer and the most ordinary iron (not counting the usual materials for etching circuit boards). So, the alternatives this method No?

Developing a variety electronic devices, used, for example, when testing monitors, we used several ways to mount electronic components. At the same time, printed circuit boards as such were not always used, since when creating prototypes and devices in a single copy (and often it turned out to be both), subject to inevitable errors and modifications, it is often more profitable and more convenient to use factory-made prototyping boards, performing wiring with a thin stranded wire in Teflon insulation. Even the most famous companies do this in a similar way, which is demonstrated by the prototype of the AIBO toy robot from Sony.

The stores sell relatively cheap double-sided tinned and even with plated holes and a protective mask on the jumpers, breadboards of very high quality.

Note that such prototyping boards make it possible to achieve a high mounting density without much effort, since there is no need to take care of the wiring of the conductive tracks. However, for example, when developing power blocks and when using elements with non-standard pin spacing or their geometry, as well as when using surface-mounted elements (which we do not do yet), it becomes difficult to use ready-made prototyping boards.

As an alternative to breadboards, we used the methods of cutting the foil in the gaps between the conductive pads and the mentioned LUT method. The first method is applicable only in the case of the most simple options wiring, but does not require anything at all, except for a sharp knife and a ruler. The LUT method gave generally good results, but some variety was desired. We considered the using method too laborious and requiring the use of caustic chemicals, which is not always acceptable at home. The case allowed us to learn about another way - about the method of direct inkjet printing of a template on foil-coated fiberglass ( keywords to search for English language- Direct to PCB Inkjet Printing).

The method is divided into the following steps:

Proper seal pigmented
Thermal fixing of the printed template. In this case, the ink becomes resistant to the etching solution.
Removing ink from the printed circuit board.

There is also an alternative:

Printing in general any ink of the printed circuit board template directly on the foil fiberglass using, as a rule, a modified inkjet printer.
Powdered toner from a laser printer/copier is sprayed onto the still wet ink, and the excess toner is removed.
Thermal fixing of the printed template. This fuses the toner and securely adheres to the foil.
Etching unpatterned sections of the foil in the usual way, for example, using ferric chloride III.
Removing caked toner from the printed circuit board.

We did not consider the second option because of the reluctance to work with powder toner, which can stain everything around with an accidental wrong movement or sneeze. All of the implemented direct inkjet template printing methods that we found used Epson inkjet printers. Also, the type of ink, or rather the type of dye used in them - pigment, we are steadily associated with printers of this manufacturer, so we started the search for a suitable printer from the Epson catalog. Apparently, Epson has, or at least had, models that can print on media up to 2.4 mm thick (and not only CD / DVDs), for example, the Epson Stylus Photo R800, but this the model is no longer produced, but we did not know in advance whether it would be possible to use something from modern analogues (obviously not cheap). As a result, it was decided to look for the cheapest model that uses pigment ink. The model was found - Epson Stylus S22. This printer turned out to be the cheapest among all Epson printers- the price for it was less than 1500 rubles, then, however, it grew noticeably: in Moscow retail (the ruble equivalent - in the tooltip) - N / A (0) .

A cursory inspection revealed the need for significant changes to the design of the printer, as it provided for printing on flexible media with its bending as it moved from the top loading tray to the output tray. The sequential modification described below was synthesized from several iterations, since after the next assembly it turned out that certain changes needed to be made to the design. Therefore, the possibility of small inaccuracies in the description of this process cannot be ruled out. The modification has two main goals. Firstly, to ensure a straight line without bends and height differences, the media supply, for which you need to change, but actually re-create the input and output trays. Secondly, to provide the ability to print on thick materials - up to 2 mm, for which it is necessary to raise the assembly with the print head and its guide slide. So:

1. Unscrew the two screws on the rear wall and remove the casing, releasing the latches with which it still clings to the bottom.

2. Disconnect the control panel cable from the main board, unscrew the two self-tapping screws securing the control panel,

release the cable from the control panel and set it aside. It is still useful, unlike the casing of the case.

3. Unscrew the 4 screws of the paper feed unit, release the wires going to the carriage motor, press the feed roller gear lock, remove the feed roller stand and the entire feed unit, remove the paper side clamp - these parts will no longer be useful.

4. Unscrew the self-tapping screw on the absorbent pad tray and on the power supply, disconnect the drain hose from the tray and the cable from the PSU on the main board, remove the absorbent pad tray and the PSU. Put them aside - still useful.

5. Unscrew the two self-tapping screws of the strip with the rollers pressing the outgoing sheet, remove this assembly and move it to a pile with “extra” parts.

6. On the right, unscrew the self-tapping screw and the screw securing the sled along which the print head moves.

Remove the spring that presses the sled.

Remove the carriage ruler spring (tapes with strokes) and the ruler itself.

Unscrew the two screws securing the main board,

and press it away from the slide (be careful with the paper sensor!). Unscrew the screw securing the sled, located under the main board.

On the left, unscrew the self-tapping screw securing the sled.

Disconnect the feed motor connector (J7) from the main board.

Disconnect the spring on the left side of the sled.

Remove the slide assembly with the print carriage and main board.

7. On the left, unscrew the self-tapping screw of the broach shaft lock,

remove the shaft and its retainer.

8. Remove all additional guides at the beginning of the broach, which are attached to the latches.

9. Using a blade from a hacksaw for metal and needle files, cut a window in the bottom from the side racks, to the bottom of the feed tray and to the feed shaft. It is convenient to use the existing grooves and holes in the bottom. Cut off the burrs with a knife, remove the sawdust.

10. Now you need to create a direct feed tray. To do this, you can use two pieces of aluminum corner 10 by 10 mm 250 mm long and part of the original paper support in the input tray (you can use any rigid plate of a suitable size). The corners are attached with M3 countersunk screws as shown in the photos below. On the vertical planes of the printer case, to which the corners are attached, grooves should be cut out so that the input tray can be moved slightly up and down to fine-tune its position.

On the right corner, you need to cut off the vertical corner, otherwise the right pressure roller will rest against it. Also on the pallet you need to cut a groove opposite the paper sensor (although, apparently, you can not do this).

And put a piece of the tube on the antenna of the paper sensor, thereby lengthening it a little.

11. Disconnect the feed shaft position sensor (one screw), cut off the stopper on the sensor housing, and fix it by sliding it as far down as possible.

During subsequent assembly, check that the disk with strokes is placed in the middle of the sensor slot and does not touch its edges.

12. Under the three attachment points of the sled, place a two washers with a hole of 4 mm each 1 mm thick. When using wide washers in two places, they need to be filed so that they do not rest against the body elements.

13. Remove the pressure rollers, put on them 2-3 layers (at least 3 layers on the central pair of rollers) of a heat-shrinkable tube with shrinkage of the intermediate layers with a hot air gun or other heating method. With a file, deepen the grooves for the rollers so that they rotate freely. Insert rollers into holders.

14. In the parked position, as well as in the process of cleaning the nozzles and initializing new cartridges, a pad with a rubber gasket is pressed against the bottom surface of the print head, where the nozzles are located. From below, a tube is connected to the pad, going to the vacuum pump. When cleaning, the pump sucks ink from the cartridges, and during storage, the nozzles are protected from drying ink in them. Therefore, it is important to ensure that the rubber seal fits snugly against the head, but due to the upward movement of the sled and print head, this condition may not be met. It is necessary to increase the travel of the pillow in the crib. To do this, you will have to remove or at least move the pump away - unscrew the two screws and squeeze out the two latches.

Then remove the spring that tightens the pillow bed, remove the bed-pillow assembly, and disconnect the tube extending from the pillow. Next, cut with a knife about 1.5 mm in the right places sections of the body of the pillow and the crib, increasing the vertical stroke of the pillow. Then assemble the knot back. Since automatic cleaning of nozzles and initialization of cartridges led to strange results when using non-original cartridges, we decided to disconnect the pump from the pad, for which we used a piece of tubing and a tee. To remove excess ink or when manually washing the pad, you can connect a syringe to the tee, or simply clamp its outlet with your finger and, by scrolling the feed shaft back (by the gear in front on the left), use the printer pump.

15. Reassemble the printer in reverse order. When installing the feed shaft, carefully clean the seats of chips and dust and apply a layer of grease to them and to the corresponding areas of the shaft. After installing the roller, you need to adjust the feed tray. By loosening the screws securing the tray to the side walls of the case, using a rigid plate of a suitable size (for example, a piece of fiberglass), you need to ensure that the movement of the plate from the feed tray along the feed shaft and along the shaft in the output tray is even, without differences in height. You should also ensure that the guides of the feed tray are strictly parallel and perpendicular to the feed shaft. Having found such a position of the feed tray, the screws should be tightened and it is advisable to fix it on the side of the nuts with a drop of varnish. Then continue building. WITH right side due to the shift of the sled upwards, or rather, the mounting hole will not coincide with the hole in the case rack - you can file the hole and fix the sled with a screw, or you can leave it as it is.

The tray of the absorbent pad, having previously shortened its right post, we installed in its original place, fixing it at two points with hot glue. The power supply did not fit in its original position, so we did not find anything better than simply fixing it with a plastic tie on the left stand of the printer frame. We screwed the control panel to the eyelet on the PSU.

The original output tray causes the output to kink, so it needs to be upgraded to ensure a smooth horizontal output. To do this, it is enough to put something a little less than 3 cm high under the tray, and put a couple of thick magazines or a stack of paper on the tray. However, after a while, we replaced this design with a tray made from the casing of a non-working DVD player. What needs to be done with the casing in order to turn it into a tray is clear from the photographs, however, here everyone can use their imagination and improvised material.

Result:

Shift the sled up to b O a larger value than described above is associated with some difficulties. Problem areas are at least the feed shaft position sensor, the right bracket of the carriage ruler, and the parking assembly. Perhaps something else. As a result, the thickness of the material on which the modified printer can print is about 2 mm or a little more, therefore, with a textolite 1.5 mm thick, the substrate should not be thicker than 0.5 mm, while it should be rigid enough to move blanks for printed circuit boards. A suitable and affordable material turned out to be thick cardboard, for example, from a folder for papers. The liner must be cut exactly to the width of the input tray, as any horizontal misalignment will affect print accuracy. In our case, the substrate turned out to be 216.5 by 295 mm in size. The original feed unit cannot be used, so the liner must be manually fed under the pressure rollers, but the paper sensor must not be activated. Because of this, it will be necessary to make a cutout in the substrate for the antenna of the paper sensor, in our case at a distance of 65 mm from the right edge, 40 mm deep and 10 mm wide. In this case, printing starts at a distance of 6 mm from the bottom of the cutout, that is, 6 mm before the edge of the media that the printer detects. Why this is so, we do not know. To fix the blanks on the substrate, it is convenient to use double-sided adhesive tape. The pinch rollers press the liner against the feed roller with great force, so the rollers must not run in or out of the workpiece to ensure a smooth print feed. To ensure this condition, before, after and possibly from the sides of the workpiece, you need to glue the material with the same thickness. This will also make it easier to position the workpiece for serial and/or duplex printing.

The original cartridges ran out fairly quickly, but overall the results with the original inks were very good. good. However, it was decided to purchase refillable cartridges and compatible inks.

The soul did not rest on this, attempts were made to modify the ink in order to increase the content of the polymer component in them. As a result of these experiments, the nozzles with black ink were clogged by 90%, with magenta - by 50%, one nozzle did not work in the "yellow" row, and only the cyan ink nozzles remained fully operational. However, one color is enough for printing templates. Since magenta ink showed the best result, it was they who were refilled in the cyan ink cartridge.

1. Prepare the workpiece surface. If it is relatively clean, then it is enough to degrease it with acetone. Otherwise, degrease, clean with an abrasive sponge, and, to form an oxide layer, place in an oven for 15-20 minutes at a temperature of 180°C. Then cool and degrease with acetone.

2. Using double-sided adhesive tape and auxiliary textolite scraps, fix the workpiece on the substrate.

3. Convert the template to the pure color that will be used when printing. In our case, in blue (RGB = 0, 255, 255). Conduct a test print (you can not print the entire template, but only the overall points, such as corners), if necessary, in the program used for printing, correct the position of the template, wash off the previous result with acetone, repeat, if necessary, the correction procedure.

4. Print the template on the blank. The best results are obtained with the following settings:

5. Dry the workpiece in air for 5 minutes, you can use a hair dryer to speed it up. Then detach the workpiece from the substrate and carry out preliminary fixing in the oven for 15 min (time from turning on the oven) at 200°C at peak. Cool the workpiece.

6. For precise positioning of the second layer, you can drill several small diameter holes, for example, 1 mm in diameter, at the mounting points of the future board. Fix the workpiece with the surface for the second layer up, while the double-sided adhesive tape must be glued to the completely painted areas of the first layer. If the workpiece is tightly clamped between the two plates front and back, then double-sided adhesive tape is not necessary. Degrease the workpiece with acetone.

7. Position and print - repeat steps 3 and 4.

8. Dry the workpiece in air for 5 minutes, you can use a hair dryer to speed it up. Then detach the workpiece from the substrate, fix it on stands, for example, made of paper clips, place it in an oven, and fix it for 15 minutes (time from turning on the oven) at 210°C at peak. Cool the workpiece.

9. Examine the workpiece, paint over places with a suspiciously thin layer of ink (for example, near holes or adhering dust particles) with a waterproof marker. Etch the workpiece. In order for the surface of the workpiece to keep a distance from the bottom of the container, you can insert toothpicks into the holes (1 mm in diameter used to position the second layer), so that the sharp tip comes out 1.5-2 mm, and the thick one is bitten off to the same height. When etching, periodically turn the board over and check readiness.

Wash off the ink with acetone.

Important notes.

1. In order for the ink used to become resistant to the etching solution, it must be kept for about 15 minutes (time from turning on the oven) at a temperature of about 210 ° C at the peak (obtained using a thermocouple located next to the workpiece). The interval is narrow, since when it is exceeded by 5-10 ° C, the textolite begins to collapse, when it is lowered, the ink is washed off with an etching solution. The exact conditions in a particular case must be selected empirically. For control, you can use the test with a cotton swab. If a cotton swab moistened with water easily washes off the ink, then you need to increase the temperature, if it does not wash off, or only slightly stains, then resistance to the etching solution has been acquired. Even if a cotton swab moistened with acetone is difficult to wash off the ink, then the resistance to the etching solution is very good. This way you can select the ink and fusing conditions that give you the best results. It should be noted that we used an electric grill oven, turned on only the upper heating element, and when the ink was finally fixed, the oven thermostat was set to 220°C.

2. Printing reproducibility reaches about 0.1 mm, so if necessary, you can print it a second time over the first side of the template, with intermediate drying directly on the substrate with a hot air gun (with adjustable temperature) or a household hair dryer set to the maximum temperature. Drying is needed so that the pressure rollers do not lubricate the previous layer.

3. The production of two sides can be done sequentially. First, print and fix the first side, and protect the foil on the second, for example, with acrylic spray paint. Etch the first side, remove the protection from the second side with acetone, print and fix the second side, protect the first with ink, etch the second side, and remove the protection from the first.

4. You need to print as follows: first send the print job, wait until the printer reports that there is no paper, then carefully slide the substrate with the fixed workpiece under the pressure rollers, scrolling the feed roller by the gear in front on the left, and then press the button to continue printing. If there are short breaks between print sessions, the printer will not perform a short cleaning procedure, so you can load the substrate with the blank first, and then send the print job.

5. Special cleanliness must be observed, as any dust that has fallen on wet ink on the workpiece can lead to a defect.

Several double-sided printed circuit boards were made in this way, and although the tracks at than 0.5 mm were not used, the possibility of obtaining tracks with a width of 0.25 mm was demonstrated in the test areas, and this is clearly not the limit of this method.

P.S. An example of a double-sided board with 0.25 mm tracks (during the design, the norms of 0.25 mm for the width of the tracks and for gaps were laid down, but with manual fine-tuning, the distances between the tracks were increased as much as possible). Note that in the manufacture of double-sided boards, apparently, it is still more reliable to print and etch the sides sequentially. Side 1:

Side 2:

Three types of defects can be seen:

1. Linear distortion, which is apparently caused by the fact that one side was printed in a fast two-pass mode, and the other in a slow single-pass mode. That is, it is better to print both sides in the same mode.

2. In places, the tracks are slightly widened due to ink spreading. This defect can be avoided by carefully preparing the surface - degrease with a piece of cloth soaked in acetone, then wipe thoroughly with a dry cotton swab.

3. From one edge of the track and the pads were etched noticeably more. This happened due to overheating, as a result of which the ink became very dark and began to peel off. This means that it is necessary to carefully monitor the uniformity of heating (choose a place in the oven where the heating is more uniform) and in no case allow overheating - the ink should noticeably darken, but not acquire a dark gray tint.

However, these defects did not turn out to be critical, and as a result, without any wiring correction, we got a fully functioning device.

Date added: 2011-02-20 | Views: 29684

A. VOVK, Angarsk, Irkutsk region

The proposed method for forming a mask that protects future conductors on a printed circuit board blank during its etching can be widely used by radio amateurs and specialists involved in the design and manufacture of prototypes of devices and equipment, repair of failed components. It is cheap, convenient, easily reproducible, does not require the use of harmful, aggressive or scarce reagents, expensive equipment and tooling.

In the overwhelming majority of cases, printed circuit boards are manufactured by etching unprotected areas of the foil on the board blank. To form a protective mask, photoresist, paints and varnishes, special inks, printer toner, and other substances and mixtures that are resistant to etching solution are used.

The determining factor in the process of preparing the board blank for etching is the choice of the method of applying a protective mask to it. IN Lately laser-ironing and photoresistive methods have become popular, but to obtain an acceptable quality mask, they require a rather lengthy development of the process.

The way I propose to apply a protective mask differs in that the printer prints it directly onto a specially prepared surface of the board blank foil. This does not require auxiliary and intermediate mask image carriers and operations associated with them. For printing, an inkjet printer with conventional water-soluble inks based on dye or pigment was used.

Since copper foil is poorly wetted with ink, it is necessary to apply a thin layer of edible gelatin solution on its surface, which prevents the ink from spreading on the foil, knocking them into drops and ensures uniform distribution over the surface without gaps, which can later lead to marriage.

The idea of printing onto a board blank in a CD tray on a printer that has this feature has been around for a long time. Since you often have to deal with small boards, they can fit from two to six in a tray, even if left untouched central hole to fix the disk It was only necessary to find a suitable inexpensive printer and make sure that its program allows you to transfer the pattern of printed circuit board conductors without distortion.

The choice fell on three inkjet printers that have the same cost and technical capabilities, - CANON PIXMA iP 4500, EPSON Stylus Photo R270 and HP Photosmart D5463. The print-to-disk programs for the last two of them turned out to be too primitive - an inconvenient interface and a minimum of functions.

The most serious was the CD-Label Print program from the kit

CANON PIXMA iP 4500 - normal control panel, scalable. A ruler is provided, which is very important when working with boards. From the Autodesk Actrix 2000 program, the drawing (via the function in the Paste Special menu) could be transferred without transformation, but from the Sprint Layout 5.0 program this could not be done.

Only the central hole for fixing the disk in the tray was embarrassing, it took up too much space and did not allow processing larger printed circuit boards.

It was decided to try to print not in the CD-Label Print program, but to use the main print driver, and everything worked out fine. Now the maximum dimensions of the board without alteration of the drawer have increased to 85x85 mm, with alteration - 120x120 mm. Why choose Autodesk Actrix 2000? Firstly, it is very versatile, allows you to draw circuit diagrams, drawings, printed circuit boards. Secondly, it has a large information base electrical and electronic components. But most importantly, they are easy to create, the elements look natural, freely transferred to the working field. There are automatic snapping to the grid, line ends, hole centers, convenient scaling when drawing and printing, selection of line thickness, color, font, background, etc.

First, in the Autodesk Actrix 2000 program, a drawing of the future printed circuit board is designed (consider a one-sided version). Save it in your working directory in case you accidentally change or delete it.

Next, in the menu (File-Page Setup...), the page dimensions are set (131x242.5 mm), they completely repeat the dimensions of the drawer for printing on CDs - they create a mask template (Fig. 1). The circle is drawn in the place where it is actually placed (check with a ruler). Save the template as an object with a name so that it can be opened.

If the board is small, the workpiece (its thickness is not more than 1 mm) is glued with a piece of double-sided adhesive tape to a free space. It should not protrude above the surface of the bottom of the tray. Then the outline of the board is printed (directly onto the plastic). The next workpiece is installed in this place. It is better to choose its dimensions with a small allowance, and then bring it to the desired size with a file or sandpaper.

If the board is large, you will have to cut off the ledge for mounting the disk in the center of the tray.

With board dimensions of 120x120 mm, you will have to modify the tray - remove (cut off) the plastic to a depth of 1.5 mm in

No. p / p	Operation	Equipment, materials, mode
1	Application of a special coating on a foil dielectric and drying of the coating	60...80% edible gelatin solution By hand with a brush (nylon) or a rotating roller (nylon). 5 min at room temperature or hot air gun 0.5...1 min at 60...70 °C
2	Printing a protective mask, soaking a special coating under a layer of ink	Inkjet Printer for CD Printing
3	Application of the polymer and its diffusion into the liquid structure of the ink and a special coating	Styrene acrylic polymer (toner). Manual brush (squirrel hair) or rotating
4	Removal of excess polymer	By hand with a brush (squirrel hair) or a rotating roller (squirrel hair)
5	Evaporation of the liquid components of the ink, baking the paste	0.5...1 min at 180...200°C
6	Washing the board with water, removing excess polymer and special coating	Water Manual brush (squirrel hair) or rotary roller (squirrel hair)
7	Etching the board on the formed protective mask	Ferric chloride solution, 60...70°C
8	Removing the protective mask	Thinner 646. 647, cotton swab or soft cloth

four corners shown in Fig. 1 in blue. The easiest way to do this is on a milling machine, but it is also possible by hand, since the plastic is quite soft. You can use a simple cutter, the same as for cutting organic glass, but with a wider - 3 ... 4 mm - cutting edge, or an electric drill with a set of coarse-grained abrasive nozzles. The inner shiny square in the recess is designed to recognize the presence of a disk, therefore, when printing a board, it must be closed with it, otherwise the printer will pull out the tray.

Double-sided boards are made in two passes. First, one layer is printed and baked (see below for more on this), then another one is also baked. For a more accurate alignment of the sides, clamps should be provided.

In the table and in fig. Figure 2 shows the main operations for forming a protective mask by the inkjet-diffusion method for single-sided printed circuit boards. It is easy to see that the inkjet-diffusion method of forming a protective mask does not require pre-pressing and heating; allows the use of foil materials with a pronounced dielectric structure (large fiberglass mesh, significant fiber thickness, etc.) and small defects, micro-scratches on the foil; does not introduce raster, diffraction, geometric distortions (unlike the use of a photomask). In the manufacture of double-sided printed circuit boards, the positioning of the layers can be easily ensured by the established reference points directly in the computer program in which the conductors are routed, without mechanical alignment and the use of microscopes and special equipment. The time spent on preparing the board for etching is minimal.

Mask ink, unlike printing on paper, is held on the surface of the workpiece due to a special coating. The image remains raw for quite a long time (several hours), so you can’t touch the surface with your hands, you need to take the workpiece only by the side edges. A finely dispersed styrene-acrylic polymer (toner) is used as a fixative. It has the ability to intensively diffuse into the ink while enveloping its particles. In other words, the ink acts as a dispersant, and the polymer acts as a dispersed phase. The ink does not spread due to surface tension and high viscosity at the points of contact with the coating.

It soaks under a layer of ink, and the polymer also diffuses into it.

Toner is applied with tangential movements (squirrel brush) in all directions to a raw, freshly printed mask. Before that, it is advisable, without touching it, to lightly powder with toner and gently shake off the excess.

As a result, a pasty colloidal solution (suspension) is formed on the workpiece, resistant to destruction to the necessary extent, completely repeating the printed pattern. The ink does not have any significant effect on gap areas, since the polymer immediately fixes the edge of all future conductors and prevents them from spreading, giving the image a clearly defined look.

Excess polymer is carefully removed, for example, with a squirrel brush or a rotating roller (optionally, vacuum suction can be used). Small areas can be scraped off with a wooden toothpick under a magnifying glass. Poorly cleaned residues can be baked and not washed off with water.

Then, with a hot air gun (or over the flame of a gas burner, being careful) baking is performed at a temperature of about 180 ... 200 ° C, the liquid components that make up the ink evaporate. Due to the low concentration of the polymer in the gaps, its baking does not occur. It is necessary to bake I until the characteristic smell of melted plastic appears. The coating should be dense and acquire a slight sheen, otherwise everything will be washed off during the washing stage.

Washing with water should remove any excess polymer that has not entered the ink. At the same time, the gelatin coating is washed off from the gaps. Protective mask presents

I is a caked mass that is resistant to an etching solution and has high adhesion to the surface of the workpiece. To increase the thickness of the mask layer, it is allowed to re-apply ink to the already formed and baked pattern (gelatin is no longer applied). This can be useful with a large workpiece area to increase the resistance of the mask, but will require very accurate re-installation blanks in the tray.

The process of forming a protective mask is implemented on a commercially available general-purpose inkjet printer CANON PIXMA iP 4500.

Software: operating system - Windows Vista Home Premium, PCB wiring - Autodesk Actrix 2000, print driver - CANON PIXMA iP 4500.

Print Mode: Color Intensity - Manual, Intensity - +50, Contrast - +50, Brightness - Normal, Print Quality - High, Media Type - CD Recommended, Paper Source - I Disc Tray, Page Size - CD-R-F Tray (131.0x242.5 mm).

The minimum width of conductors and gaps is 200 µm.

Printing is done on the place where the drawing of the future board is transferred. Any color should be chosen, except for black, since it is difficult to control the degree of application of the black polymer on a black background. Double-sided printed circuit boards must be firmly fixed in the printer tray so that they fall accurately when turned over into the same place. Combination of images of conductors on the first and second layers is carried out in the Autodesk Actrix 2000 program itself according to the reference points set on the coordinate grid. The alignment accuracy determines the selected grid cell size value.

It takes no more than 10 ... 15 minutes to manufacture a high-quality printed circuit board with dimensions of 85x85 mm (plus the time for preparing the drawing of future conductors and the etching time).

For the method of manufacturing boards described above, a styrene-acrylic polymer (toner) with a particle size of 3 ... 4 μm is suitable, which is used in laser printers and photocopiers of most foreign companies - XEROX, HP, CANON, SAMSUNG, etc. It should be noted that toners different manufacturers have slightly different melting points.

A special coating is an aqueous solution of edible gelatin, and the already swollen gelatin is not diluted, but it is taken that is not brought to full swelling, that is, the most active components that make up the gelatin that have passed into the solution are used.

It is better to use edible gelatin sold in the form of crystals or granules. One part of gelatin will require five parts of boiled cold water (by volume).

Gelatin swells 5 ... 10 minutes (depending on its quality). The solution is stirred periodically. It should acquire such a viscosity that when applied to the workpiece it does not leave gaps, but at the same time it does not reach for the brush, and after application it spreads a little more. The gelatin crystals that have not passed into the solution are removed from the brush on the edge of the dish and removed.

Left for a long time, the solution turns into jelly (gelatin swells completely) and becomes unusable.

The coating should be uniform (not have stripes), and after drying, acquire a slightly iridescent hue. It dries quickly, but you can speed it up with a hair dryer. If any defects are found when viewing under a magnifying glass, it is better to wash off the coating and apply a new one. You can wash off already printed drawing.

When etching, do not overexpose the boards in the solution and use too intensive mixing methods to prevent peeling of the protective mask.

It should be noted that in Sprint Layout 5.0 there is no hard link between the created project and the size of the selected page, so a test print will be required.