(*steve*) submitted a new Showcase Item:
Toner transfer for PCBs having BGA packages on them
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Toner transfer for PCBs having BGA packages on them
OK, I'm a glutton for punishment.
Quite some time ago I purchased some small chips designed to drive a couple of LEDs at a constant (programmable) current. I was silly enough not to take enough notice of the package to order them in a BGA package.
This has spurred me on to try to improve my toner transfer technique to produce boards with traces of 0.1mm in width. For the imperial amongst us, that's a shade under 4 thousandths of an inch.
My existing printer 300dpi could not get near this, and another 600dpi printer was better, but not "better enough". When I saw some 1200dpi laser printers on special for $42, I decided to see if that would be good enough. I ended up as the proud owner of a Fuji Xerox P205B printer.
Initial impressions of the print quality were good, aside from a worrying issue of 0.1mm gaps between traces closing up on some areas of the page.
My first tests were done using a heat sealer to try to transfer the toner. This was not successful and it was apparent that I was going to have to apply more heat.
Tonight I did a second test. The aim was to check the degree of smudging of the image, rather than to produce a board, so I did not follow all the board cleaning steps. Principally, I did not take steps to remove any oil on the board, and used a "handled" printout that was both a little dusty and may have had fingerprints on it.
I used three types of paper, and 2 were clearly not working, so I'll concentrate for the most part on the one that did (a "home brand" glossy inkjet paper).
OK, you probably want to see some pictures... I'll apologise for these in advance. They're pretty blurry.
This is early on in the process as I'm stripping away the top layers of the paper (it's pretty heavy paper). The thick blob of paper at the top is where the tape was attached that held the paper in place. It prevents the paper from wetting and should really not be near the image area.
Already you can see the toner through the paper and a closeup of the board shows you that the toner image is pretty crisp. The BGA package is in the middle of the pattern on the right (it's a 14 pin package) and the pads around it are for 0805 components. To the left you can see some text with approximate sizes printed....
Read more about this showcase item here...