Hi Werner,

The cracks show up as opens in ICT. The board is very thin and flexible (bows under its own wt when a populated board is picked up from one end), so it has to be handled with kid gloves, not always possible in a production environment.



As I mentioned in an earlier E-mail, we did a pad strength test using pull testing on the SnPb laminate, and LF Laminate with LF process temperatures, and SnPb laminate with SnPb temperatures. The SnPb laminate subjected to the SnPb process exhibited only pad cratering failures. The SnPb laminate and LF laminate subjected to Pb-Free processing exhibited mixed-mode failures; both cratering and IMC fracture was observed. The IMC fractures were secondary failures occurring after the pad had failed. Fracture of resin was shallow and does not expose the glass fibers.



The customer cannot change the board thickness, the location (the BGA is in the lower left hand quadrant of the board) and size of the part. after SMT, the board goes thru a stuff line, over the wave in a wave pallet, and then de-panelized and ICT’ed. It will eventually be inserted in a slot on a Chassis for the life of the assembly.



We have a (rather expensive) option of attaching strain gauges to the BGA and measuring stresses during different operations, but I am currently working on a simple fact that IF we get peel strengths, not significantly different from our SnPb variant of the same product (which works without any issues), then we have a solution



Amol S. Kane

M.S (Industrial Eng.)

Process Engineer

Harvard Custom Manufacturing

941 Route 38

Owego, NY 13827



Phone: 607-687-7669 Ext. 349

Fax: 607-687-9733

Email: [log in to unmask]



From: [log in to unmask] [mailto:[log in to unmask]]

Sent: Wednesday, June 18, 2008 4:36 PM

To: Kane, Amol (349); [log in to unmask]

Subject: Re: [LF] [TN] SN100 for Reflow Application



Hi Amol,

Enhance tooth profile will do nothing for you, since the separation is not between the ED Cu foil and the resin.



You say: "The cracks appear later in the process and are typical stress fractures (near the edges of the BGA)." What are these 'later processes'? Something is making the components/PCB warp.



Werner Engelmaier

Future workshops:

Reliability Issues with Lead-Free Soldering Processes, June 19, London

Interconnect Failures and Design for Reliability for PCB PTHs, June 19, London

Solder Joint Reliability: Parts 1 through 4, July 17/18, Thal, Switzerland

Pb-Free Soldering Processes—Survival, Quality, Reliability, August 18, Orlando

Reliability Issues with Lead-Free Soldering Processes, September 22, Schaumburg

Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle Fracture, ENIG), September 22, Schaumburg







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