Hi Inge,
You did not give us the location of these 'deformed' balls. If they are at the BGA corners or under the corner of the die they may have an impact.
Are they more collapsed or more stretched?
In terms of reliability, solder joint height is the critical geometric parameter. Any stress concentration geometry, and all these balls have them to some degree, is about a factor of 2 influence.
Will you come to the IPC Reliability Conference in Frankfurt in May? Maybe we can talk about it there.
Werner
-----Original Message-----
From: Hernefjord Ingemar <[log in to unmask]>
To: [log in to unmask]
Sent: Tue, Feb 16, 2010 6:17 am
Subject: Re: [TN] Pre-Tinned BGA?
Hi all,
We buy ordinary Tin/Lead-balled BGAs from XILINX. Now, in the Xray inspection
after soldering, we can often see, that some out of 600 balls are not as sround
as aspected to be. Instead, some balls are deformed. Not much, but enough to
start questions whether such balls are accepted or not. Have not seen anything
about roundness requirements in any norm. A deformed ball can tell you about
possible electrical issues or about lowering the mechanical fatigue life. On the
other hand, irregular ball shape may mean nothing. If the electrical connection
is free from failure, one may neglect the unshape.
The boards are VP soldered. Have any idea if VP is part of our problem?
A typical example is a multilayer board, size about 8x10 inches, populated with
five BGA560s. The total of 'deformed' balls numbers some ten pcs. We have had
discussions for weeks without coming to a decision if such balls are okay or
not. There are no indications of electrical issues (yet.
What is your opinion?
/Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: tisdag 16 februari 2010 01:51
To: [log in to unmask]
Subject: Re: [TN] Pre-Tinned BGA?
Thanks Bob,
Didn't know about 2 great suppliers left.
Werner
-----Original Message-----
From: Bob Landman <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Feb 15, 2010 7:37 pm
Subject: Re: [TN] Pre-Tinned BGA?
Hi Werner,
Well, Lattice Semiconductor (bless them!) still offers Pb/Sn balls on BGAs and
PLDs and so does Analog Devices (bless them too!).
Others may be more problematic hence we prefer Lattice products for their
features and their support. They are ideal for small companies like ours. Their
design tools are very affordable compared to others. Every year their tools get
better.
Bob Landman
H&L Instruments, LLC
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Monday, February 15, 2010 7:18 PM
To: [log in to unmask]
Subject: Re: [TN] Pre-Tinned BGA?
Hi Joyce,
where have u been--sure (3) is ideal, but where do you get the components from?
Werner
-----Original Message-----
From: Joyce Koo <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Feb 15, 2010 6:30 pm
Subject: Re: [TN] Pre-Tinned BGA?
(3) And (1). But not the other. (3) required nothing to be done on the assembly
level. All the rel data are valid. (1) may need reduced rel qual. The others,
as material change, most of the mil or hi rel house need full qual (shake, drop
all the nine yard). It would cost around 30 to 50k plus risk budget (depend
upon how complicated is your assembly) and 3 month delay. At least it use to
be. My ancient 1.8 cents.
--------------------------
Sent using BlackBerry
----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Mon Feb 15 17:49:57 2010
Subject: [TN] Pre-Tinned BGA?
Hello All,
I had a question to see if anyone has tried anything different. Most of our
customers are some how related to the military. So we have one product that the
customer just found out was a PB-Free device. They want us to "pre-tin" the
spheres. Now I have tried several process for forward and backward processes.
None of them include re-tinning of a BGA Device. We do re-tin other leaded and
some non leaded devices. So below are the three options I have recommended but
still have reliability concerns as the end product is to be coated with
Paralyne.
1. Re- Ball to PB/SN
2. Sue a selective rework machine and place pate with isolated heat if the
substraight could handle.
3. Purchase the component in PB/SN material 4. Reflow the product with slightly
higher temps (5c per 10 zones) once out of over and cold to room temp underfil
the device.
Again if anyone has any more ideas I am game!!
Carl Ray
Lewisburg TN 37091
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