Maker Pro

Toner transfer for PCBs having BGA packages on them

(*steve*)

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(*steve*) submitted a new Showcase Item:

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...
 

chopnhack

Apr 28, 2014
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Nice work @(*steve*) ! I had toyed with the idea of getting a laser printer, we too have some low expense options from local office supply stores. I haven't seen any with 1200dpi. Have you found that to be the ideal coverage or does it still need a higher dpi? Has playing with the darkness increased your resolution and decreased your unwanted cut through?
 

Bluejets

Oct 5, 2014
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My old original HP mono laser printer died and I replaced it with a Brother HL-2130 for toner transfer.
More strife than Flash Gordon. Must have tried 50 different ways with no luck. Thought for a while I'd lost my touch.
Read somewhere that Brother toner is not re-fusable i.e. it's a one off thing so it now sits with my wife's laptop.
Replaced it with a HP P1102W and everything is back to normal again. i.e. print, transfer, etch, finished.
Use press n' peel blue toner transfer paper.
 

chopnhack

Apr 28, 2014
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My old original HP mono laser printer died and I replaced it with a Brother HL-2130 for toner transfer.
More strife than Flash Gordon. Must have tried 50 different ways with no luck. Thought for a while I'd lost my touch.
Read somewhere that Brother toner is not re-fusable i.e. it's a one off thing so it now sits with my wife's laptop.
Replaced it with a HP P1102W and everything is back to normal again. i.e. print, transfer, etch, finished.
Use press n' peel blue toner transfer paper.
Yes, I had read quite a bit about the Brother units not being useful for our purposes. I wonder why they use toner that is not refusable? I would think that to have that characteristic would be more expensive than what the competitors are using. I wonder if it was necessary for their fuser temp if they did auto duplexing?
How good is your resolution set at best? Spec says that its 600x600x2 which is HP's way of saying 600dpi but we use software to goose the number - in real life, what is the smallest resolution you were able to achieve?
Thanks
 

Bluejets

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Never changed it...just looked now and it is set on Fast Res600 and the other option is for Fast Res 1200.
My biggest concern usually is with getting the job out of the etchant as soon as possible to avoid undercut.
Years ago I had a supply of "Dick Smith" copper clad boards and I soon found the copper layer to be like busbar when it came to etching.
These days use the stuff that comes from China, so I guess there is something to to had from a cheap product.
i.e. copper layer is thin and etches easily, still enough for most jobs and if beefing up required, I widen the track and run a layer of solder on the track afterwards.
 

chopnhack

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Never changed it...just looked now and it is set on Fast Res600 and the other option is for Fast Res 1200.
My biggest concern usually is with getting the job out of the etchant as soon as possible to avoid undercut.
Years ago I had a supply of "Dick Smith" copper clad boards and I soon found the copper layer to be like busbar when it came to etching.
These days use the stuff that comes from China, so I guess there is something to to had from a cheap product.
i.e. copper layer is thin and etches easily, still enough for most jobs and if beefing up required, I widen the track and run a layer of solder on the track afterwards.

I have had good initial results with etching a board with hydrogen peroxide and muriatic acid. I think these chems would work far better for your thicker platings. Have you ever given them a try? Cheap and probably more environmentally friendly than the ferric chloride. The muriatic acid is neutralized at the end with baking soda and the entire deal can be disposed of in your solid trash. If you have the facilities, the mix could go for copper reclamation, but I try to remove the least amount as possible when I etch so I don't feel bad about putting it in the bin. From chem class, acid to water so muriatic acid is added to the hydrogen peroxide.
 

HellasTechn

Apr 14, 2013
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I have had good initial results with etching a board with hydrogen peroxide and muriatic acid. I think these chems would work far better for your thicker platings. Have you ever given them a try? Cheap and probably more environmentally friendly than the ferric chloride. The muriatic acid is neutralized at the end with baking soda and the entire deal can be disposed of in your solid trash. If you have the facilities, the mix could go for copper reclamation, but I try to remove the least amount as possible when I etch so I don't feel bad about putting it in the bin. From chem class, acid to water so muriatic acid is added to the hydrogen peroxide.

Ok but ferric chloride is far less dangerous for skin contact if you wash it with water.

Hydrogen peroxide and muriatic acid can give you nasty burns on skin if you are not careful !
 

chopnhack

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Ok but ferric chloride is far less dangerous for skin contact if you wash it with water.

Hydrogen peroxide and muriatic acid can give you nasty burns on skin if you are not careful !

I've had no problems, but gloves are the best precaution, safety glasses and a respirator too!
This mixture is more environmentally friendly in my opinion - it can be neutralized with baking soda and disposed of. If you really want to, you could bring this mix to the junk yard for copper reclamation - I would assume that if you had adequate amounts, they would be happy to take it for you.
 

HellasTechn

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There is the difference. With ferric chloride you need none of the above gear (just careful not to breath it and even if you do for short time period still does no harm).

Hydrogen peroxide and muriatic acid has given me burns (white stains on skin that hurt but go away if you wash with plenty of water) and i just dont like it.
:)
 

(*steve*)

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I agree. Ferric chloride is potentially messy, but is also relatively safe.
 

chopnhack

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To each their own, I have used both and I am currently in favor of the muriatic acid because of cost, ease of use and environmentally friendly disposal. I didn't think it was faster, but when I thought back to when I used to use the ferric chloride solution (over ten years ago) - I did remember having to leave it for a lengthy time - so this other acid is much faster.

I don't want to take away from steve's thread re: toner transfer and bga, if you want - @HellasTechn make a new thread describing the benefits of ferric chloride etching vs. h2o2

@(*steve*) - I had to replace a printer, so I went with a laser this time around - a Dell unit and I am excited to see what it can do resolution wise!! I will post elsewhere to keep this area from getting cluttered unless its relevant to your process. ;-)
 
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