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There is a test called SERA (Sequential Electrochemical Reduction Analysis)
which is non-destructive that can be used to predict solderability. The test
produces a plot of cathode voltage vs. time. The plot reflects the type of
oxide and the charged passed is a measure of the amount of oxide present. The
test can be used for HASL and can be used as a presence tester for OSP.
Contact
ECI
1 Madison St.
East Rutherford, N.J. 07073
201-773-8686
[log in to unmask] Wrote:
|
| Address,
|
| I have several boards types and part numbers that are
| older than 18
| months. They are SMOBC with SnPb coated pads, SMT
| both sides. Based
| on observation two types have been Horizontal HAL and
| One Vertical HAL
| at an angle. Without an XRF, I going to assume 100
| microin. on large
| pads (>.025 pitch & caps) and 500~800 microin. on
| smaller pads (.020
| pitch). From past experience and several Round Robin
| Studies these
| boards should have a minimum solderability shelf life
| of 6 months (a
| year in some cases). To validate this, I am going to
| apply solder
| paste to the component side, via solder paste
| stencial, and run
| through reflow as if a production panel. If
| solderability has been
| degradated by copper migration or similar through the
| thin SnPb layer,
| there should be signs of dewetting and/or no wetting.
|
|
| My question: Is this still a valid test and are
| there other tests
| used to verify bareboard solderability? Does the
| three, six or 12
| months periods still apply if the boards are stored
| properly?
|
| Should I find solderability problems, one corrective
| action is to
| return the bareboards to the supplier for
| re-soldering and hope the
| extra thermal cycle does not affect the board
| further.
|
| Please advise. Thanks in advance.
|
| p.s. Jack Crawford; I need your new email or will
| someone pass it
| along.
|
|
|
|
|
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