Hello all,

Just a quick note for reference. The MicroBGA® CSP was designed to obviate
concern over the solder joint as a compliant element. In the µBGA® CSP, the
compliant layer in the package absorbs most of the stain of CTE mismatch
between silicon and FR-4 substate. As a result, the solder ball metallurgy
is not a great concern beyond allowing a good joint to be easily and
reliably formed in the assembly process and have sufficent strength to hold
fast the component in use.  

Kind regards,
J. Fjelstad  


At 12:41 AM 3/30/99 -0800, you wrote:
>     Hi, Guenter, Werner...
>     An opinion within the group of "leading lights" of UK technology,
>     claim that "the lead free legislation is good timing" as Sn/Pb alloys
>     do not have the reliability of other alloys, particularly with regard
>     to modern components such as CSPs and Micro BGA.
>
>     I have always understood that Pb makes Sn/Pb alloys very plastic and
>     thus extreemly reliable under the stresses of thermal cycling.
>
>     If there are more reliable alloys, what might they be?
>     Which alloys present us with a higher degree of plasticity?
>
>     Regards
>     Edward Brunker
>     PSION Computers
>
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