I don't think we can definitely rule out 4) yet without knowing what the
PB materials were; what the pad geometries were; the actual dimensions
of the solder mask defined pads; and the actual failure mechanism. I do
agree 1) and 2) are the most probable causes, but understanding the
above could help explain the exacerbation of the failure mechanism.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Friday, May 15, 2009 1:11 PM
To: [log in to unmask]
Subject: Re: [TN] 0201 capacitor failure after reflow
Hi Anat,
You can eliminate 3), 4) and 5) from my list, leaving1)and 2).
Werner
-----Original Message-----
From: Anat Douek <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, 15 May 2009 10:47 am
Subject: Re: [TN] 0201 capacitor failure after reflow
Hi Werner,
The PCB finish is immersion gold over nickel .
The capacitor finish is pure tin over nickel
The solder is lead - tin paste.
Anat
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Thursday, May 14, 2009 11:41 PM
To: [log in to unmask]
Subject: Re: [TN] 0201 capacitor failure after reflow
Hi Anat,
I take it this is SAC solder.
From what you describe, it sounds like an overstress failure due to the
combination of:
1) large CC/PCB CTE-mismatch,
2) large solder fillets,
3) stiff SAC solder,
4) Pb-free PCB base material that is more brittle,
5) large delta-T between SAC Solidus and PCB Tg.
Werner
-----Original Message-----
From: Anat Douek <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, 14 May 2009 5:18 pm
Subject: [TN] 0201 capacitor failure after reflow
Hi,
We have 8 layers RF circuit, the internal layers are FR4 and the top &
bottom layers are ROGGERS material. The PCB pads are solder mask define.
There are many 0201 components on this circuit without any problem, and
one
type of capacitors is rejected after the reflow process. The problem is
that
the capacitors pads are separated from the body completely or there are
cracks between the pads and the capacitor body. The pads of the
capacitor
located on the bottom and on the sides of it, there is no pads on the
top of
the component.
What can be the cause of this failure?
Is different size of pads of the capacitor on the PCB can cause this
problem
?
Anat
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