ENIG is a flat, easy to solder surface. It sure beats OSP when trying to wave solder after two reflow cycles. I haven't seen black pad from our ENIG supply base in almost a decade - they seem to have figured it out. I'm not saying black pad isn't still out there, just that a good board supplier can manage it. I think a lot of what people chalk up to black pad (I'm not necessarily talking about this Technet thread) is people simply overstressing boards. With ENIG you'll get brittle fracture at the intermetallic with BGAs when an in circuit tester hits them with the equivalent of a sledge hammer. With OSP or HASL there'd have been pad cratering instead.
Lately I've seen a rash of really poorly done Pb free HASL that leaves us trying to solder to intermetallic. Unfortunately no surface finish is perfect. Pick your poison.
Scott Post
P.O.U. 0000-001E-0CTC
2151 E. Lincoln Road
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Tuesday, October 12, 2010 1:57 PM
To: [log in to unmask]
Subject: Re: [TN] Mech. damage or poor wetting?
Warner,
I keep hearing these stories about P concentrations and ENIG black pad
issues. Why do so many folks use the ENIG process over HASL? Flatness?
Thanks,
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Tuesday, October 12, 2010 1:32 PM
To: [log in to unmask]
Subject: Re: [TN] Mech. damage or poor wetting?
Hi Phil,
Two points to be made:
(1) Dye and Pry is not misleading-it simply tells you whether you had cracks
present prior to the 'Pry' or not; it is not designed to elucidate anything
about the cause(s), that is what a root cause analysis is for.
(2) Of course, 'Black Pad' would be more prevalent at the BGA periphery-it
sees more heat with more NI dissolved and leaving higher P-concentration.
Werner
Upcoming workshops:
November 2 & 9, SMTA Webtorial,
"Fundamentals in Solder Joint Reliability"
December 7 & 14, SMTA Webtorial,
"Acceleration Models, Accelerated Reliability Tests and
ScreeningProcedures"
-----Original Message-----
From: Phil Bavaro <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Oct 12, 2010 1:06 pm
Subject: Re: [TN] Mech. damage or poor wetting?
Thus.....etc
I would want to inspect the rest of the board for more evidence of the
black pad, such as the smaller chip caps....for it to only occur at the
perimeter of the bga seems unlikely. On a chip cap pad which has had
solderpaste melt and interact with the nickel underneath, the dewetting
should be apparent.
Dye and Pry can be misleading as to the cause of the dye penetration,
especially when there are numerous possible mechanical questions.
Phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, October 12, 2010 9:40 AM
To: [log in to unmask]
Subject: Re: [TN] Mech. damage or poor wetting?
It sure looks like Black Pad to me.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Monday, October 11, 2010 2:41 PM
To: [log in to unmask]
Subject: Re: [TN] Mech. damage or poor wetting?
Was this BGA reworked/repaired. Is it in close proximity to another
BGA that was RW? Did the card/board see two consecutive thermal
excursions?
X"
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne - IIW
Sent: Monday, October 11, 2010 1:55 PM
To: [log in to unmask]
Subject: Re: [TN] Mech. damage or poor wetting?
Never mind. I just read the original post. I'm betting the whole
shebang is due to poor wetting--that's why the correlation to the fanout
escape.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne - IIW
Sent: Monday, October 11, 2010 2:52 PM
To: [log in to unmask]
Subject: Re: [TN] Mech. damage or poor wetting?
What's going on with the picture of the cross section? The ball isn't
wetting down the side of the plated pad.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna
Sent: Monday, October 11, 2010 2:41 PM
To: [log in to unmask]
Subject: Re: [TN] Mech. damage or poor wetting?
Here are a few pictures
http://ipc-technet.groupsite.com/gallery/16011
this job is a mixed bag. Currently we suspect soldering, cratering, ICT
and t-cycling damage
Chris
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Monday, October 11, 2010 2:22 PM
To: TechNet E-Mail Forum; Chris Mahanna
Cc: [log in to unmask]
Subject: Re: [TN] Mech. damage or poor wetting?
Hi Chris - do you have any pictures you can share?
Dave Hillman
Rockwell Collins
[log in to unmask]
Chris Mahanna <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
10/11/2010 11:29 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Chris Mahanna <[log in to unmask]>
To
[log in to unmask]
cc
Subject
[TN] Mech. damage or poor wetting?
We have a BGA dye-n-pry job that shows board side sj damage with a
strong correlation to fan-out clocking.
We also have some microsection evidence of poor wetting.
All damage/dye is on perimeters.
Is this an indication of heat sinking and subpar wetting, or can it be
completely mechanical? Both?
Thanks
Chris
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