Hard drive centrifuge for sensitizing copper clad boards

hdd-to-apply-light-sensitive-ink

We would wager that most of the home etched PCB projects we see around here use the toner transfer method. But the next most popular technique is to use photosensitive ink which resists the etching acid once it has been exposed to light. Most people buy what are called pre-sensitized boards, but you can also get ink to make your own. [Jardirx] does this, and uses an old hard drive to apply an even layer of the light-sensitive ink.

The narration and subtitles of the video found after the break are both in Portuguese, but it’s not hard to figure out what’s going on here. He begins by using double-sided foam tape to secure the piece of copper clad board to the hard drive platters. You’ll want to center it as best as you can to keep the vibrations to a minimum. From there [Jardirx] applies a coating of the ink using a brush. The image above is what results. So as not to get ink everywhere, he then lowers a soda bottle with the bottom cut off to catch the excess. Power up the drive for a few seconds and the board will have a nice even layer ready for a trip through a UV exposure box.

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Printable wax as PCB etch resist

What if there were only two steps for making your own printed circuit board; print, etch? That’s what [Jeff Gough] has been working on and he presented the process in his talk at 27C3. In the first portion of the video after the break [Jeff] talks about various industrial PCB manufacturing processes in a depth you may not have heard before. We found it to be interesting but at about thirty minutes into the clip he begins the presentation of his modified printer. It’s an inkjet that can print wax onto copper clad board. The wax acts as a resist for chemical etchants, and provides very high resolution. He’s using a heavily modified print head, which brings to mind that diy piezo inkjet head which also has wax printing in its future plans. This certainly seems promising and if the process can be simplified it might do away with the toner transfer method.

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Direct to PCB inkjet printing

[Rhys Goodwin] has been working on a system to print resist onto copper clad using an inkjet printer. This is a toner transfer alternative as it still uses toner, just not quite as you’d expect. The first step is to modify an inkjet printer, separating the carriage from the feed rollers in order to increase the clearance for the substrate. Instead of printing with etch resistant ink, as we’ve seen before, [Rhys] prints with black ink and then covers the board (ink still wet) in laser toner. Once there’s good adhesion he blows off the excess and bakes the board in a sandwich press, with spacers to keep the iron from touching the surface of the copper clad. This cooks the resist into a hard plastic layer and the board is ready for the acid. Watch him walk you through the process after the break.

[Rhys] uses the same method for silk screen, printing in red and baking the ink onto the substrate without added toner. This produces a nice looking board but it’s still quite a bit of work. It certainly sheds more light on the process than that laser-printer method from back in May. We hope you’ve been inspired by this and come up with the next innovation that makes this process easier.

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Building a UV exposure box

There are two methods of using etchant resist when making circuit boards. We use the toner transfer method that requires ironing on laser toner to the copper, but you can also use chemical resist that reacts to ultraviolet light. [Bogdan] decided to start doing more of the latter so he built a UV exposure box to make the process easier.

It is possible to use flourescent light bulbs for this, but he decided to use UV LEDs, a method we’ve also seen before. But there’s always room to innovate, and [Bogdan] built-in a couple of nice features that are new to us. Because the UV light can be bad for your eyes, he included a set of red visible-light LEDs on the bottom half of the box that are used to align two layers of exposure mask when making double-sided boards. There’s also a switch that automatically shuts off the UV light when the box is opened. And as the coup-de-grace, he added a programmable timer to regulate the exposure, using his newly created box when etching the PCB for it.

DIY plotter with laser

plotter-with-300w-laser

[Viacheslav] built a plotter that is fast and accurate. He wanted to take it one step further and added a laser in place of the pen. The 300 mW unit does a nice job of wood-burning any pattern sent to it, but isn’t strong enough to serve as a laser cutter for anything other than thin-film. We wonder if it can be used to cut solder paste stencils for surface mount PCB production.

In the video after the break you can see some plotting that uses a pen. In addition to writing on paper, [Viacheslav] has tested this as a method of applying etch resist to a copper clad board for PCB production. He’s able to achieve 0.8 mm pitch but the production process is limited by the resist pen’s tendency to wear out quickly and to only prevent etching for a short period of time (compared to toner transfer resist).

Just like with his touch sensitive keypad project, he’s taken the time to thoroughly document his work. Build notes, pictures, CAD files, and source code are all available for your perusal and hackage.

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