Fred, 
 
 We are currently testing most BGA product on 100 mil grids with 3.75" long 
 pins on a single fixture. However, the need for multiple fixtures (split 
 nets) is on the rise due mainly to increasing density of BGA's and SMD's 
 around BGA's. I agree with tbresnan@multek that there is a need for double 
 density test; on a small but growing scale. We have not yet experimented 
 with splitting tests between the grid and prober.
 
 Our most significant factor in creating a single fixture is the density of 
 test points around the BGA. This is coupled with the fixturing software's 
 ability to efficiently assign all test points to grid.
 
 
 Regards,
 
 [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: Re: Bare Board Test PCBs with BGAs
Author:  [log in to unmask] at corp
Date:    2/12/96 5:25 PM


 
 
Fred...
 
The only strategies available today are the "double-density" BBTesters that give
you an extra pin in the center of the std .100 grid and the "flying probe" type 
testers. Most folks today are using a combination test, flying probe in the high
density area of the PWB and standard BBTester for the remainder of the board. 
Unfortunately, the testers of the world do not have a single solution for high 
volume throughputs.
 
[log in to unmask] 
 
______________________________ Reply Separator _________________________________
Subject: Bare Board Test PCBs with BGAs
Author:  [log in to unmask] at internet_gateway 
Date:    2/12/96 3:16 PM
 
Can anyone share successful Bare Board Test strategies and Equipment 
Requirements when 
launching into BGA testing?  For example:  A 19 X 19 array, 1.27 mm pitch, 357 
pin, PBGA with 23 mil diameter NSMD solder pads on 
a board with two signal, one power, and one ground plane.  Can this be done 
using a 100 mil grid BBTester?  Particularly useful would 
be your experience dealing with the obstacles and solutions to unforeseen 
problems.  
 
 
FRED J. PAUL:   [log in to unmask]   FLUKE CORPORATION 
Sr. Process Engineer    POB 9090   M/S 55
PCB Operations     EVERETT, WA 98206
direct: 206 356-5734   fax: 206 356-6070  Corporate: 206 347-6100