Anybody ever make a 100 pin TQFP PCB ?

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I've made 64 pin TQFP PCBs using UV and, photo sensitive boards. I guess for a 100 pinner, that the issue would be can the etchant get between the lines ( traces ) or would I just get a mess of partially dissolved copper all over the place between the traces ? Etchant is ferric chloride.

1) Studio 4.18 build 716 (SP3)
2) WinAvr 20100110
3) PN, all on Doze XP... For Now
A) Avr Dragon ver. 1
B) Avr MKII ISP, 2009 model
C) MKII JTAGICE ver. 1

Last Edited: Tue. Aug 9, 2011 - 04:06 PM
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I don't expect that FeCl will work for that pitch. I am actually surprised it worked for the 64pinners!

There are much better and safer etchants than ferric chloride, that -could- work for such a precision application. Some have the advantage that are clear, so you can monitor the process and also they don't etch under the film as fast as FeCl does. I don't recall any names right now (the one I use doesn't have a brand sticker), but a simple google search should provide many. *

Are you aware of pcb companies like iteadstudio and seeedstudio? Given their prices, does it worth to fab your own boards for that pitch?

IMHO, considering the prices of the above companies and the fact that soldermask is included, it doesn't worth the time or the trouble to develop your own. Plus the fact that (I expect) you will have much waste on failed attempts, just because of the limits of this process.

*edit: 1) I cannot be more specific because I am not sure which one of those that will show up on google is equivalent to the one I use. I bought it locally, though I do know it is commonly used and suggested around the net.
2) I tried for MSOP8 with decent results. But even though MSOP8 is also fine pitch, it has only 8 lines.

-Pantelis

Professor of Applied Murphology, University of W.T.F.Justhappened.

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HNO3

3Cu + 2NO3- + 4H+ >> 3Cu2+ + 2NO2 + 2H2O

:twisted:

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Or 100-200g/l Persulfate, 20ml/l 96% Sulphuric Acid.

Cu +(NH4)2S2O8 >> CuSO4 + (NH4)2S2O4

** Don't substitute the sulphuric acid for HCL unless you want to die in a green cloud.

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Or H2SO4 + H2O2.

Cu + H2O2 + H2SO4 >> Cu2SO4 + 2H2O

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Consider the ordering of a 'professional' PCB, they are not that expensive anymore

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Never had a problem etching MSOP, TSSOP or TQFP in about any pitch.

It's more a matter of choosing the right screen than getting complicated etching materials.

at 55 to 65 degrees centigrade 250g/l "fine etching crystals" with the chemical make-up of PerSulfate (Ammonium or Sodium per Sulfate usually).
--> X-S2-O8 (where X is most commonly Na2)
Costs near to nothing if you get yourself a real supplier or store (none of those big commercialists) and with one liter you can etch your heart out if you design your board well enough.

At the point the etching solution goes from tinted blue to translucent cobalt blue it will slow it's etching process to a point where very fine etching will be harder.

Also note that at temperatures 70 degree C and up PerSulfate can infiltrate and break down certain masks faster than it eats copper. Most noticeably the ink-pen type will suffer greatly.
(Believe conrad had one at some time, basically an upgraded Edding Marker)

--- EDIT:
With persulfates it is best for the environment if you only use the sewer for post-etching rinsing or not at all.
To be honest anything that has eaten copper is best not discarded in the sewer.
Persulfate/CopperSulfate mixture can be dried in a wide plastic basin, and you can easily shake them off into a small bag and get them to a collection point for household chemicals.

--- EDIT2:
Also note that PerSulfate is a higly active oxidizer even without a corresponding reductor, so it will react with your clothes to bleach them, or in the case of cotton (jeans, nice shirts, etc) or other soft natural fibers, eat them.
Use old clothes.
When the crystals dry in the upper skin it can be tingly or itchy, but the etchant does not migrate into the body, the tingly will go away without any side effects. (other than the tangy smell of old copper in your hands for a day)
However it is still wise to use latex gloves or similar when handling it.

Embedded design is as much a life choice as any other and I demand the right to legally marry my work.
-------
If it helps, I can PM you my answer in a number of different languages. Ask if you have trouble reading my high-speed-babble in English.

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PNP wrote:
Are you aware of pcb companies like iteadstudio and seeedstudio? Given their prices, does it worth to fab your own boards for that pitch?
Not until now, thank you and I doubt it, PNP. It looks like I just need to use the PCB houses for such chips for any prototyping work.

Thanks everybody for letting me know.

1) Studio 4.18 build 716 (SP3)
2) WinAvr 20100110
3) PN, all on Doze XP... For Now
A) Avr Dragon ver. 1
B) Avr MKII ISP, 2009 model
C) MKII JTAGICE ver. 1

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Sulphuric acid and hydrogen peroxide make up a reusable solution you do not ever need to discard. You can collect the copper after etching by electroplating a stainless steel plate in the solution, and you can reactivate the solution by bubbling oxygen through it or adding more peroxide.

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Also do NOT ever use tap water or hydrochloric acid with persulfate. This forms chlorine gas and kills you. Use anything with persulfate outside IMO.

And do not mix in acetone with h202 and an acid unless you want to blow up.