Some Sulfite Au Plating solutions available by Technic (Technigold 25E pH
6.5-7.5, Technigold 25ES), Rohm and Haas (Aurofab BP pH 8.5) and Cookson
Electronics Materials (Microfab Au 100 pH 7.7 - 8.3) are well within the
range compatible with almost all resists.

----- Original Message -----
From: "Novak Farrington" 
To: 
Sent: Wednesday, November 30, 2005 7:32 AM
Subject: [mems-talk] Recommendation for Gold bump process


> Hi all,
>
> could anyone recommend a combination of thick photoresist (~65um but
thinner
> would be OK as I could use a multilayer application) and commercial gold
> electroplating bath which work well together? The electroplated gold needs
to
> be around 50um for a 'bump' type process on a GaAs substrate.
>
> I've had experience in the past with a cyanide based bath (puramet 402)
but this
> seemed to be incompatable with most common resists, showing the usual
documented
> problems.
>
> For this reason I'm open to using either sulfite or cyanide based
electrolytes.
> I was thinking about using BPR 100 (possibly with thinner) or a multilayer
> AZ45xx/AZ92xx resist.
>
> >From some of the publications I've seen, the sulfite electrolytes exhibit
a
> rather high pH (up to 9.5) which is rather worrying - from experience, to
what
> degree does this affect the photoresist?