Hi Steve,
First, IPC-9701 was developed for qualifying components as to their SJ
reliability capability under the assumption of good solderability. It is not
a good test for solderability problems--vibration would be good to screen out
bad wetted SJs.
>1.If we design a test board with 10 LCC units on it, do we daisy chain each
>unit individually and tie all 10 units to a common point? or do we daisy
>chain all 10 units consecutively?
ANSWER: Daisy-chains should not include components in series, they should be
individual--to get more data, you can even partition the component monitoring
each side indiviually (see IPC-SM-785)--you 10 components given 10 data
points is not enough, you need at least 32.
>2. Do we add jumpers or testpoints in various locations around each
>individual LCC to help determine where failures may be?
ANSWER: No, solder joint failures are, except when caused by component
warpage, intermittents, so probing for them is essentially futile--you need
to monitor in-situ with an Event Detector. Also, the failure location us at
the component corners unless you some SJ properly wetted and others not.
>3. If we do tie all 10 units consecutively, do we add jumpers or testpoints
>between each set of daisy chained LCC to help determine which unit has
>failed?
ANSWER: Same answer.
>4. The IPC-9701 spec calls out that a minimum of 50% of the land pad sites
>are to require vias, does this mean that out of the 36 pads being used, at
>least 18 have to have a via going through them....and does this mean
>directly on the pad itself or coming off the pad like what would most likey
>be done during standard PWB layouts?
ANSWER: For your purposes, this does not apply.
>5. The spec also calls out a nominal of 40% copper coverage on odd number
>layers, I'm assuming this means even if that layer is not being used...and
>the same would go for the even number of layers which is to recieve 70%
>nominal.... am I right in assuming this?
ANSWER: Yes, but for your purposes, this does not apply.
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com
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