As perhaps the only person still around that attended the meetings
resulting
in the equivalence factors and IPC Cleaning & Contamination Chair at that
time, perhaps a few points would facilitate the discussion:
1. The Navy set up the ionic testing development program to solve a serious
failure problem in S.E. Asia.
It worked.
2. In the timeframe when the test was developed and put in place by the
military, most of the rest of the electronics industry in the US used the
mil
specs since they were free.
3. As the IPC set up and adopted Classes 1-3 (basically toys up to
military/high rel), I asked the committee if we used the mil test result for
Class 3,
could we use 1.5x that limit for Class 2 and 2-3x for Class 1?
The response was that with proper cleaning, the mil limit could readily be
achieved while serving to monitor daily production. So the industry
continued
to use the (free) mil spec test standard.
4. The ionic contamination test was a valuable monitoring tool, since the
SIR tests were done on coupons, not on actual assemblies, and took 1-2 weeks
to
complete. Needless to say, a high volume electronics producer could turn out
a significant volume of PWAs during that time, often shipping them into the
field as soon as assembly was completed.
5. As noted in my SMT column (offered yesterday) T. O. Duyck of Northern
Telecom was charged with implementing water soluble flux for NT electronics
production. During that time he observed and reported the differences in
flux
residue release rates, pointing out that rosin ca 90% of rosin flux
residues
release from the PWA surface during the 10-15 test time for ionic test
equipment, while water soluble flux residues may take up to 2 hrs. to
achieve the same
level of release. Thus the release rate should be checked to ensure the
flux
used, time test time and the instrument employed provide reliable results
and guidance to the production engineer.
(See T. O. Duyck and M. Boulos, "Water Washes Reliability into Telephone
Circuit Packs", IPC-TR-206, April, 1978)
Based on this work, I investigated the release rate of SA flux residues,
finding it even faster than rosin fluxes. (See W. G. Kenyon, "Synthetic
Activated (SA) Flux Technology: Development, Commercialization, Benefits and Future
Applications", Internepcon Japan, 24 Jan. 1986)
6. In the late 1980's, the materials and acceptance of the no clean or low
residue or acceptable dirt concept became widely accepted and implemented on
the designs of the time. Outsourcing to contract assemblers (both in the US
and
overseas) became widely practiced, so much of the former 'in-house' cleaning
expertise disappeared.
7. This was seen at IPC as the number of company sponsored volunteers
dwindled. Could we take on projects today to develop an updated ionic test
for pr
ocess monitoring? Find enough participants to conduct statistically sound
round
robin testing?
Bill Kenyon
Global Centre Consulting
3336 Birmingham Drive
Fort Collins, CO 80526
Tel: 970.207.9586 Cell: 970.980.6373
**************Need a new ride? Check out the largest site for U.S. used car
listings at AOL Autos.
(http://autos.aol.com/used?NCID=aolcmp00300000002851)
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
