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Lead-Free Alloy composition used for leaded IC Packages

Kelvin Chow

#6328

Lead-Free Alloy composition used for leaded IC Packages | 22 August, 2000

Mr. Lee,

Although most of the lead free alloy used for solder paste and wave soldering have been identified, a suitable alloy used for leaded Ic packages (like QFP, PLCC..etc) have not been identified yet.

Do you have any suggestion on this lead-free solder coating?

Regards

Kelvin Chow Cookson Semiconductor Packaging Materials

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Dr. Ning-Cheng Lee

#6329

Re: Lead-Free Alloy composition used for leaded IC Packages | 22 August, 2000

Hi Kelvin,

Regarding to the surface finish of the leads, Sn or Pd may be the direction that the industry takes.

First of all, the answer must be "Pb-Free", limiting our choices. Sn has good solderability, and it won't have too great of an impact on the ultimate alloy formed at the joint after reflow.

Pd can provide good bond strength. Be cafreful though, as the Pd plating process can produce wettability/solderability. It is process sensitive.

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genesmelik

#6330

Re: Lead-Free Alloy composition used for leaded IC Packages | 22 August, 2000

Dr. Lee,

Following up on this thread, I have read that a Pd-Ni lead finish is one promising option, but that Ni-oxidation might be problem. Can you explain this more?

Thanks,

Gene Smelik Cookson Performance Solutions

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Dr. Ning-Cheng Lee

#6331

Re: Lead-Free Alloy composition used for leaded IC Packages | 22 August, 2000

Plating houses seem to exhibit various results. Unacceptable Ni oxidation levels appear to be related to poor Pd plating processes.

Ni oxidation can occur at 3 process stages: 1) prior to the Pd being applied (Ni already oxidized) 2) during the plating process 3) after the plating process - due to any high porosity of the Pd surface (leaving exposed Ni)

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