Jowan,
Your list ranks OSP as 4?
I was wondering if you had tried an OSP designed for LF process
temperatures, or had bad results because you used a less LF temp robust
OSP chemistry such as the ENTEK 106 which was designed for temps <230C ?
OSP is definitely the favorite in Asia, it does not add cost, and if the
solder profile is right you get the same spread as immersion silver,
without the oxide problems that cause poor second-side SMT solder
defects and top-side W/S defects.
Nitrogen in my evaluations seemed beneficial for ImAG and ImSn...
Any one else share some thoughts?
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Jowan Iven
Sent: Wednesday, February 16, 2005 7:20 AM
To: [log in to unmask]
Subject: Re: [LF] PCB Solderability tests
Hello Edward,
In collaboration with 3 other companies I have tested 9 types of
solderpaste LF and 4 types of pcb finish.
Solder spread is the best on 1 ENIG.................2 ImSn
........................................................3
ImAg....4 OSP
Nitrogen is beneficial for the soldering proces.
But selecting the right solderpaste has more effect than the use of
nitrogen alone.
There were solderpastes that wetted worse in nitrogen than other pastes
without nitrogen.
We used a Solder Spread Test to determine wetting on a dedicated
testboard.
No Wetting Balance Test has been performed.
And I think not many companies will use a wetting balance test.
We did investigate tombstoning for all of the finishes and solderpastes
and
selected several solderpastes that are less susceptible to tombstoning.
Is there a reason to do the Wetting Balance Test, after all?
Regards
Jowan Iven.
On Wed, 16 Feb 2005 13:45:47 +0200, Edward Szpruch <[log in to unmask]>
wrote:
>Hi all,
>We are PCB manufacturer and we are supplying our boards with several
>alternative finishing ( ENIG , OSP , Immersion Tin, Immersion Silver ).
>Recently we staret internal discussions concerning lead-free era.
>What about objective solderability tests for bare PCB ???
> It seems to me, that "wetting ballance" test based on using of melted
>eutectic Tin-Lead is not relevant anymore because of two reasons :
>1. Tin-Lead solder will be excluded and replaced by ???? What kind of
solder
>will be recognised as "official lead free solder" ??
>2. Today's boards ( at least those we are manufacturing ) are mainly
all
>kinds of SMT, it means using solder pastes and I.R. reflow and not
through
>hole using solder wave.
>
>Solder Spread Test seems to be more relevant, but what paste should be
used
>and which parameters ????
>
>Opinions???
>
>Regards
>Edward
>
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