[tinwhiskers] Re: - RoHS & BGAs!!!

  • From: "Parnagian, Edward" <ed.parnagian@xxxxxxxxxxx>
  • To: "tinwhiskers@xxxxxxxxxxxxx" <tinwhiskers@xxxxxxxxxxxxx>
  • Date: Wed, 18 Feb 2009 19:19:53 +0100

Hello, Hani!

At the moment we are using immersion silver, but our CM is now trying to direct 
us toward electroless nickel, immersion gold.

The decision on underfill is still in limbo.

Both of our main circuit assemblies have ECG frontends, so given the high 
impedance and low signal voltages associated with ECG, we know that getting 
adequate cleanliness is going to be a battle.  Consequently, we are again 
pushing the CM out of their comfort zone by asking for an aqueous flux followed 
by a rigorous cleaning process to remove all ionic residues.

Best regards,
Ed

-----Original Message-----
From: tinwhiskers-bounce@xxxxxxxxxxxxx 
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of AL-Yousef, Hani E
Sent: 2009 Feb 18 11:19 AM
To: tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] Re: - RoHS & BGAs!!!

Ed,

I am afraid we don't use enough volume either for a manufacturer to run
a special device for us.

How about underfill, when should be concerned about that?

Are you using ENIG for PCB finish?

Do you have recommendation with the silk screening process regarding
cleanliness and RoHs?

Thanks I appreciate the advice.

Hani

-----Original Message-----
From: tinwhiskers-bounce@xxxxxxxxxxxxx
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Parnagian, Edward
Sent: Wednesday, February 18, 2009 9:52 AM
To: tinwhiskers@xxxxxxxxxxxxx
Subject: [tinwhiskers] Re: - RoHS & BGAs!!!

Hani,

Most of us in high reliability industries - mine is medical
defibrillators - don't generate enough volume to be able to convince an
Analog Devices to run separate ball formulations.  My advice is to talk
with someone like Amkor who at one time was willing to obtain dies from
the original manufacturer and then package the dies with tin lead (SnPb)
balls. The catch is that some original manufacturers are unwilling to
give them permission to do so and/or won't honor warranty on the device.
Do NOT try reballing devices that have already been balled; you will not
get consistent metallurgy between the balls and the die.  Some will be
good, and some will be terrible.

Alternatively, build your design for lead-free but use only low silver
BGAs.  SAC105 balls held down with SAC305 perform almost as well as
SnPb.  If you can find SAC105 with a sprinkling of magnesium, the impact
strength is actually superior to that of SnPb, and the thermal cycle
life is still much better, as well.

The overall market place has still not come to face the harsh realities
(limitations) of the early decisions associated with SAC305, but a lot
of people are desparately working on it.  My guess is that the
transition to a real solution without lead is a decade away - at best.
Until then lots of pain for people whose products have to last more than
a couple of years.

Best regards,
Ed

-----Original Message-----
From: tinwhiskers-bounce@xxxxxxxxxxxxx
[mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Bob Landman
Sent: 2009 Feb 18 9:51 AM
To: tin whiskers forum
Cc: <tinwhiskers@xxxxxxxxxxxxx>
Subject: [tinwhiskers] Re: - RoHS & BGAs!!!

Hani,

Some companies still offer BGA in tin-lead (Lattice Semi is one of
them). I recently helped to convince Analog Devices to put tin-lead
balls on a MEMS device for an aerospace firm as the devices were
popping off after reflow.

Your hardware designers need to push the envelope harder. Demand tin-
lead solder balls.

Bob

P.S. Later today I'll get you other papers on the subject.

Sent from my iPhone

On Feb 18, 2009, at 9:24 AM, "AL-Yousef, Hani
E"<Hani.AL-Yousef@xxxxxxxxxxxxxxxxxxxx
 > wrote:

> Bob,
>
> We are forced to use SAC BGA since that is the only thing available
> for
> that part. I guess your advice would be, look for another part that
> comes in tin lead.  I have to work on the firmware guys for that.
>
> Would happen to have any white papers, experiments documentations,
> application notes that state the concerns that you shared?
>
>
>
> Thanks,
> Hani
> -----Original Message-----
> From: tinwhiskers-bounce@xxxxxxxxxxxxx
> [mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of Bob Landman
> Sent: Wednesday, February 18, 2009 12:19 AM
> To: tinwhiskers@xxxxxxxxxxxxx
> Subject: [tinwhiskers] Re: - RoHS & BGAs!!!
>
> Hani,
>
> Your equipment should be exempt from RoHS requirements.  Do not use
> SAC
> solders or SAC BGAs if you expect a 20+ year life.  The mechanical
> vibration from switching your reclosers will shake the BGAs off their
> pads.  Mechanical shock is the nemisis of SAC alloys, especially at
> low
> temperatures.  Outside on a pole in Alaska is going to cause failures.
>
> See
>
http://ap.pennnet.com/display_article/312379/36/ARTCL/none/none/1/Detect
> ing-Brittle-Fracture-Failures/
>
> Bob Landman
> H&L Instruments, LLC
> www.hlinstruments.com
>
>
>
> -----Original Message-----
> From: tinwhiskers-bounce@xxxxxxxxxxxxx
> [mailto:tinwhiskers-bounce@xxxxxxxxxxxxx] On Behalf Of AL-Yousef,
> Hani E
> Sent: Friday, February 13, 2009 11:27 AM
> To: tinwhiskers@xxxxxxxxxxxxx; TechNet E-Mail Forum;
> RoHSUSAPushback@xxxxxxxxxxxxxxx; SMART Group smart-e-link
> Subject: [tinwhiskers] - RoHS & BGAs!!!
>
>
> Hello All,
>
> I am in the hunt for information on how to best evaluate whether
> underfill is needed for SAC BGA when soldered with SAC paste.
>
> Also, part of my evolution is to find the right solder, flux and
> chemistry to clean afterwards. Further specify a cleanliness level.
>
> I guess one has to find to the right test to use to evaluate these
> parameters.
>
> Our products are expected to last for 20+ years while mounted
> outside on
> a power distribution pole mounts.
>
>
> I can use all the help I can get.
>
> Thanks
> Hani
>
>
>
>
>
>



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