Re: gEDA-user: Cheap 4 layer manufacturer?

[Darrell Harmon <mail@xxxxxxxxxxxx>]

On Tue, Oct 11, 2005 at 04:02:37AM -0400, marvindickens@xxxxxxxxxxxxx wrote:
> > > I bumped the ball size down from the Xilinx recomended 0.4mm to 0.34mm,
> > > and everything worked out fine. 
> 
> In our experience, bumping down pad size can be a dangerous thing. I'd be 
> carefull and test a few before I had that many made. The issue is not whether 
> you can attach a bga device to down sized pads, but if it will stay attached 
> through time. In essence, I am suggesting that down sizing the pad can 
> emulate bad printing, device warpage and/or PCB warpage. Printing is talked 
> about here:
> 
> http://www.aimsolder.com/techarticles/tech sheet BGA voiding- reducing through 
> process optimization.pdf
> 
> The rest is talked about here:
> 
> http://www.akrometrix.com/pdf/Tech_Papers/CSP Board Level Reliability.pdf
> 
> 
> Best regards
> 
> Marvin

That was just for the prototype. I intend to use a manufacturer who can
do smaller vias for production to allow full size pads. I would never
sell something with a hack like that.

-- 
Darrell Harmon
http://dlharmon.com/dspcard
Credit card size DSP/FPGA board