[SI-LIST] Re: Production testing of loaded PCB's power supply impedance
- From: "Greim, Michael" <mgreim@xxxxxxxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 16 Jul 2001 10:09:22 -0400
Hi Peter,
Here are some thoughts regarding how you may get a better
comfort factor regarding your populated PDS. You do raise
an interesting question in that often times, the PDS system
contains the vast majority of parts on a board. So how do
you know that things are installed completely and correctly.
Well, here is my 0.02 cents worth. First AOI will tell you
if in fact components are installed in the place that they
should be. They won't tell you if the component is the correct
one but the will at least tell you that a location is populated.
One can generally assume that the pick and place data is a
constant, therefore, if one location of a given type is correct
one can assume that they are all correct. For each given
cap type, one can create an instance with a test pad on either
side. this way, the tester can check for an appropriate
capacitance value. I have found that this is a good way
to get a warm fuzzy at a production level. Running a frequency
sweep on production boards is a way overly time prohibitive
method and I can't say that you would have enough resolution to
know if things are populated as expected.....
While one does have to have some trust in the process one
does need to keep an honest man honest and assist weeding
out possible sources of human error (reel loading, etc)
comments??
Best Regards,
Michael C. Greim Sonus Networks
mgreim@xxxxxxxxxxxx 978-589-8336
Making the world safe for digital signals everywhere
And all this science I don't understand
It's just my job six days a week
The time is gone. The email's over
Thought I'd something more to say......
-----Original Message-----
From: Peter Baxter [mailto:peter.baxter@xxxxxxxxxxxxx]
Sent: Monday, July 16, 2001 6:33 AM
To: si-list
Subject: [SI-LIST] Production testing of loaded PCB's power supply
impedance
Hi,
I've asked people how do they know that all bypass capacitors were
installed on their PCBs, and how do they know that the loaded capacitors
are the correct value? Most people have told me that they don't know.
Unless a capacitor is installed on a coupon, and the coupon's power
system impedance specially measured, no one checks it.
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