We just went through a design and build of our DSP board with 7 BGAs
on it. The board we are building is a pre-production prototype, but
some steps we went through that may help you are:
- Inspect the PWB before parts are installed. There were some vias
(signal through holes) we found around the BGAs that the vendor
missed masking out. Also check the PWB using a connectivity test
- The assembly house offered x-rays on all BGAs as part of board buy-
off. This may save debugging time later if you have a short
underneath the BGA.
- We opted not to do the JTAG boundary scan. This step may save
some troubleshooting time later but you have to do your own price
justification. This test is typically done when you are building a
production lot or if you don't have time for a possible
- When you are ready to power up the board, use a power supply that
has current limiting capability. This way you don't smoke anything
if there is a short.
A tool that we had in-house that helped us a lot was an thermal
imager. We had a short, so we slowly cranked up the input power and
see where on the board it gets hot. This saved us a lot of
troubleshooting time. This equipment is expensive but you can rent
The assembly house may also have other tools which may help
troubleshooting, such as a fiber microscope that can fit and see
underneath the BGAs.
Hope this helps,
--- In c..., "Michael Dunn" wrote:
> Hello Peter,
> On 11/29/07, pn2500 wrote:
> > Anyone have any tips on production testing techniques for pc
> > using the C64xx BGA chip?
> There are dozens of specific techniques in use by 'large and small
> Today's modern devices with BGA components and fine
> tested in a variety of ways depending on intended use
> simple goals - make sure that it works and be 99.99%
sure that it
> work when installed.
> If your board is able to be 100% functional tested, low volume, and
> used in 'normal office temperature environments', I think that a
> comprehensive function test while running the temperature at the
> end and varying the voltages from min to max is a
> place. I have been in shops that do much more and
much less. The
> would look like -
> 1. run quick functional test.
> 2. if pass, run comprehensive functional test.
> > i.e. is Xray inspection of the BGA contacts standard?
> I do not believe that Xray is 'standard'. In my personal
> few years ago when BGA was kind of a 'new thing']
> was near impossible to detect opens.
> > Are there test programs using JTAG that can check for
> > do external memory bus testing?
> You can use JTAG boundary scan [BS] to perform 'static' [low speed]
> testing for opens and shorts. In a 'normal mfg flow', I wouldn't
> BS. I think that it is more usefull for fault
> on fall outs. [I have seen it used to test paths and
> the 'normal flow'].
> > Has anyone gotten advice from TI in doing design-for-test with
> > that they could share?
> This isn't any magic from TI, but it might be useful - tailor it to
> your 'careabouts'.
> Off the top of my head...
> 1. Consider test during board design
> 2. Explicitly make every signal that you might want to look at
> accessible [this obviously includes clocks].
> 3. Provision for power supply current measurements and power
> isolation. If chip power can be isolated that is very nice. A sick
> [a very rare event] often has abnormal current
> 4. Include at least 1 maintenance jumper and indicator.
> 5. Avoid write only registers when possible.
> 6. Provide loop back capability. This may be on board, external
> jumper, or may require an external 'test board' to rerout/capture
> 7. Include manual reset capability.
> 8. If there is a watchdog timer, provide a method [HW or SW] to
> 9. Make sure that the board has a 'debugable minimum
> have seen boards that required other boards to be
plugged in for
> to come up - don't do that.
> > Thanks!
> > --