Ian,
There is an idiom in my language, saying something like: "A wise person is
the one who learns from other's experience". And another one: "If you need
an advise, ask the experienced person, not the expert".
The problem is with the Ni itself. I didn't have personal experience with
it, as I keep my soul away from gold in any type (we don't have even gold
coins). I read about the Ni barrels problems from colleagues, and found some
data on it in Tyco's site. Sorry - I don't have the references: It was quite
some time ago, and I read the documents on-line and dropped the links.
Regards
Ofer Cohen
Quality Assurance Manager
Seabridge Ltd.
-----Original Message-----
From: FOX, Ian (York Rd) [mailto:[log in to unmask]]
Sent: Wednesday, June 11, 2003 10:10 AM
To: 'TechNet E-Mail Forum.'; 'Ofer Cohen'
Subject: RE: [TN] LCC HASL and Immersion Silver
Ofer, interested in your comments regarding failure of electroless Ni
barrels. Are you saying that the stress applied by the press-fit termination
causes failure or that simply the Ni itself fails? If it's the former I
can't comment having only just started to look at press-fits seriously. If
the latter then I have to say in my experience an electroless layer hangs on
in there long after Cu beneath it has circumferentially cracked.
Regards
Ian Fox
Goodrich Engine Control Systems
-----Original Message-----
From: Ofer Cohen [mailto:[log in to unmask]]
Sent: 11 June 2003 07:25
To: [log in to unmask]
Subject: Re: [TN] LCC HASL and Immersion Silver
Peter,
Although the question is to Dave, I will contribute my own 2 cents. Because
I made the decision some time ago, I would be glad to hear (=read, in this
case) comments.
As long as the components were in the sizes down to minimum of 0402 for
discrete components, and pitch of 1 mm for BGAs and 0.5 mm for other
components I lived (and still do) happily with HASL. This is my preferable
coating, because a) every PCB manufacturer does it best; b) the handling
during the assembly and the assembly processes are simple and commonly
known.
The problems started when the army of the R&D people conquered the 0.8 mm
pitch BGAs. I know that HASL is still acceptable in this pitch. However, the
circuit is sensitive and I wanted to make it more robust. I considered 4
choices:
a) immersion tin and OSP - problematic in handling. I have to trust my CM
that even in the third shift the SMT line operators will wear clean gloves.
I am a little paranoid about compliance of employees to procedures that are
less comfortable to implement. Apart of it, I had bad experience with some
PCB manufacturers performing this finish.
b) ENIG - not to speak of black pads, I have many press-fit connectors, and
the nickel layer is known to have long-term reliability problems in this
case, because it cracks and causes disconnections.
c) Immersion silver - was left alone and selected as default. Indeed, it
needs some time to get used to it: the wetting is not perfect, handling and
storage period are still have to be monitored. Yet, it seems to be the
optimal solution.
Yet, I want to emphasize that my default finish is HASL.
Regards
Ofer Cohen
Quality Assurance Manager
Seabridge Ltd.
-----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Wednesday, June 11, 2003 1:52 AM
To: [log in to unmask]
Subject: Re: [TN] LCC HASL and Immersion Silver
Hi, Dave,
Can you shed a little more light in this dark world and give us the story of
why you choose Immersion Silver over, say, Immsersion Tin for BGAs and
Fine-Pitch stuff. I'm interested from the Class 3 High Reliability
perspective and currently use ENIG for this type of assembly. For future
designs, though, I intend to move to either ImAg or ImSn, but haven't
determined which one yet.
TIA
Peter
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