Bath chemistry and pH and temp.
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----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Mon Nov 23 15:15:04 2009
Subject: Re: [TN] solder fracture solderable?
Hi Bob,
No, you read it correctly, and put your finger squarely in the problem.
Werner
-----Original Message-----
From: Robert Kondner <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Nov 23, 2009 3:10 pm
Subject: Re: [TN] solder fracture solderable?
Hi,
The other week there was talk about ENIG vs HASL so I have been searching
around the web for ENIG info. I read a number of items.
I recall reading that a phosphorus (in nickel) content of > 10% (I think it
was %) was required to control the Immersion Gold thickness and better
control corrosion resistance. Wow, 10% sounds high but I guess that is
right.
The photos show a P+ layer at the failed interface. Does that imply
increasing P is a problem at making "Strong" soldered connections?
How does a lowly PCB user monitor this kind of parameter of phosphorus so
it is not too much or not too little?
Or did I misread the entire scenario?
Thanks,
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, November 23, 2009 2:31 PM
To: [log in to unmask]
Subject: Re: [TN] solder fracture solderable?
Hi Inge,
Sorry it took me a while to get this posted, I've been doing assembly quotes
a good part of the morning.
Yeah, Guy has quite the story to tell about his adventure, wish I could talk
about it, but then he would have to kill me...
But anyways here's your pics:
http://stevezeva.homestead.com/Image1.jpg
http://stevezeva.homestead.com/Image2.jpg
http://stevezeva.homestead.com/Image3.jpg
http://stevezeva.homestead.com/Image4.jpg
http://stevezeva.homestead.com/Image5.jpg
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Monday, November 23, 2009 6:52 AM
To: [log in to unmask]
Subject: Re: [TN] solder fracture solderable?
I don't believe in the knife idea. Have my own way. Complicated, but works
(not always).
1. Cut out the area of interest (e.g. BGA) with good marginal. Use fine
blade diamond saw. Let it take time. Use cutting oil.
2. Clean from oil. Glue mount two thick metal plates to both sides of the
sample under test. Each plate has a hook attached to the plate.
3. Place the sample in at pull tester and pull apart until the BGA separates
from the board. Use low speed.
I've sent example on this to Steve Gregory.
/Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: fredag 20 november 2009 21:28
To: [log in to unmask]
Subject: [TN] solder fracture solderable?
I was visiting a customer earlier this week. They were attempting to cut a
the top part off of a package on package, BGA on top of BGA.
They didn't want to reflow it off because they didn't want to damage the
balls on the bottom of the bottom package.
They had made a little fixture affair with two knives adjusted to slice
between the two packages.
They placed the PoP in the tool and pushed it through the knives, rotated 90
degrees and repeated the cycle.
Most of the pads on top of the bottom package ended up with half a ball
remaining on the pad.
But some of the pads did not have any solder on them at all. The entire pad
was mat finish silver in color.
None of these features would accept solder. The number of pads without
solder varied from one or two to 30% of the pads.
I wondered if rather than cutting through, some of the connections has
simply fractured along the intermetallic, leaving a non-solderable surface
with this uniform appearance.
Some of those observing conjectured that the package was bad, They
conjectured that the silver was merely solder loaded with gold and that the
nickel had never accepted solder.
I asked where their SEM was and if they had EDAX equipment . . . nope.
Would anyone care to guess along? How likely is it that prying off a BGA
would fracture the connection right along the intermetallic and leave a
completely non-solderable surface?
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