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Services
 BEST Inc is a component reworking service provider with the ability to provide high quality, device retinning services.
Tinning of components is used amongst other things to change the lead finish of components from lead-free to tin lead. In addition, it is used to mitigate tin whisker growth, which can form when pure tin plating is used. Hot solder dipping of pure tin-finished terminations using tin-lead (Sn-Pb) solder reduces tin whisker formation by replacing tin with a tin-lead alloy. It can also be used to improve or restore the solderability of the parts, acting as the primary finish for the terminations. Lead Tinning can also be used in the restoration of corroded components to their original condition.
BEST can provide lead tinning services which meet/exceed MIL standards. Some or more of the following MIL standards may apply to the type of work that you are performing:
MIL-PRF-38535, General Specification for Integrated Circuits Manufacturing
MIL-PRF-38534, General Specification for Hybrid Microcircuits
MIL-PRF-19500, General Specification for Semiconductor Devices
More information on tin whisker growth, mitigation factors and other plating problems can be found here:
NASA’s information on Tin Whiskers
NASA - Tin Whiskers: A History of Documented Failures
The problem of tin whiskers on component leads has been well documented. While there is limited information on the exact growth mechanism, there are a number of mitigation strategies available. These strategies range from simple processes such as annealing the tin finish, to more complex processes such as plating underneath the tin finish with a stress reducing under-plating. One common option for high-reliability applications that are exempt from the European legislation is the refinishing of pure tin-plated components with a SnPb finish (3 weight % Pb or greater). A well performed lead tinning process can provide a consistent, even coating of SnPb solder to all leads on a component. Solder tinning is a long standing process outlined in MIL-PRF-38535 that provides a finish in compliance with the IPC J-STD-001/J-STD-002. Leads are re-tinned in Sn63 solder in most cases. Components are de-taped, treated, and re-taped to ensure a minimal loss in productivity. A good tinning shop will utilize ESD precautions and have no trouble refinishing any leaded SMT component, regardless of size or configuration. Lead-free tinning services have not yet emerged in the mainstream market, limiting the mitigation options for those forced to comply with the EU directives.
 In addition to lead tinning services, BEST can return the parts in either a tape and reel format or in customer-supplied matrix trays. Optical inspection services and part marking can also be performed on the retinned components.
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