TECHNET Archives

July 2008

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Igoshev, Vladimir" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Igoshev, Vladimir
Date:
Sun, 6 Jul 2008 12:40:27 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (101 lines)
It a rare occasion I completely agree with Werner :-).

Unfortunately, I see reports with the "intermetallics" Werner refers to
more often than I'd like to.

Vladimir 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Friday, July 04, 2008 10:33 PM
To: [log in to unmask]
Subject: Re: [TN] [LF] [TN] SN100 for Reflow Application

Hi Amol,
First, I would suggest you use a different lab in the future, or get
them 
educated. The statements: " The presence of intermetallic at the
interface shows 
that a "Black Pad" condition is not present." is pure nonsense.
Essentially, but not exclusivley, 'Black Pad' requires that IMCs are
formed-th
at enriches the P-content at the Ni/IMC interface.
Second, the fact that you have 3 different failure modes-pad cratering, 
brittle interfacial separation, & BGA-side cracks, occuring, sometimes
in 
combination, shows that you do not have a significant weak link. Some of
the 
RoHS-capable PCB base materials are more brittle with lower cohesive
strength, but 
seeing multiple failure modes indicates that is not the issue.
Third, you do not tell me what other processes follow reflow-however, 
whatever it is puts significantly higher stresses on the SAC-SJs than on
the 
SnPb-SJs.
CONCLUSION: The root cause is obvious-it is the switch from SnPb to SAC
and 
ALL that entails.
CRITICAL DIFFERENCES: A) SAC is about 40% stiffer than SnPb=>higher
stresses;
B) delta-T to Tg of SAC Solidus v. SnPb Solidus is more than
double=>higher 
stresses;
C) delta-T to Tg of SAC Soldering T's v. SnPb Soldering T's is more than
50% 
higher causing more warpage=>higher stresses;
D) SAC creep rates are about 50x slower than SnPb=>higher stresses.

I would suggest attending my new workshop Pb-Free Soldering Processes-
Survival, Quality, Reliability.

Werner
Future workshops:
Pb-Free Soldering Processes-Survival, Quality, Reliability, July 17/18,
Thal, 
Switzerland
Pb-Free Soldering Processes-Survival, Quality, Reliability, August 18, 
Orlando
Reliability Issues with Lead-Free Soldering Processes, September 22, 
Schaumburg
Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle
Fracture, 
ENIG), September 22, Schaumburg
Solder Joint Reliability: Parts 1 & 4, Oct. 9, Moscow, Russia
Solder Joint Reliability: Parts 1 & 4, Oct. 17, Timisoara, Rumania
Solder Joint Reliability: Parts 1 & 4, Oct. 22, Tallinn, Estonia



**************
Gas prices getting you down? Search AOL Autos for fuel-efficient used
cars.
   
   (http://autos.aol.com/used?ncid=aolaut00050000000007)

---------------------------------------------------
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
-----------------------------------------------------

---------------------------------------------------
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
-----------------------------------------------------

ATOM RSS1 RSS2