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Process makes leaded devices Pb-free

Posted: 30 Aug 2007 ?? ?Print Version ?Bookmark and Share

Keywords:ROHS directive? WEE? Pb-free component?

A study conducted by E-Certa Inc. and Sanmina-SCI presented a way to reuse Pb-containing parts by converting them to Pb-free for use in consumer-grade electronics.

The joint study was developed to verify the conversion process for leaded components to Pb-free and RoHS-compliant parts. The report "Evaluation of Stripped and Replated Component Termination Finishes" covers both forward conversion (SnPb to Pb-free) and backward conversion (Pb-free to SnPb) of SOIC-packaged devices using E-Certa's stripping and retinning processes. A sample size of 90 parts for each part type was converted for this study.

The conversion was performed by E-Certa, followed by XRF testing to ensure RoHS compliance. Sanmina-SCI performed the electrical and die visual inspections using optical microscopy, DC pin-to-pin electrical testing and acid de-encapsulation. Included were lead pull testing of the devices "as assembled condition" and "after thermal aging" to determine the mechanical reliability of the converted component termination finishes. The results show that the converted components have almost the same pull strength as the original components, according to the study.

The converted parts were also assembled on a PCB using both SnPb and Pb-free processes. Three PCB surface finishesImmersion Silver (ImAg), Organic Solderable Preserve (OSP) and Electroless Nickel/Immersion Gold (ENIG)were evaluated. Key findings indicate that the microstructures of the converted components were normal in appearance and had well-defined IMC along the board and component interface.

"The study was performed to validate that the process used does not damage the component in any way or compromise the functionality to an unacceptable level due to the heat and stress the parts go through in the retinning process," said Michael Baker, quality manager for E-Certa. "It also covers the validity of the strip and tin process going from lead to Pb-free and Pb-free to lead."

E-Certa has also released a media information series, which outlines the process of converting leaded components to Pb-free. The series called "Component Pb Conversion" covers techniques, concerns and costs associated with component Pb conversion. The series also reviews conversions that go in reverse to convert Pb-free components to Pb for use in military/aerospace, medical or RoHS-exempt applications.

According to Baker, by converting these parts to Pb-free, the process will help OEMs comply with the recycle/reuse initiatives brought about by the WEEE directive as well as keep these leaded components from going to the landfill. In addition to component lead conversion, E-Certa also provides XRF testing for compliance, material declaration, delidding for component verification, and WEEE recycling services.

- Gina Roos
Electronics Supply & Manufacturing

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