Revised IPC Standard on Immersion Silver Plating Establishes Maximum Deposit Thickness

IPC—Association Connecting Electronics Industries has released IPC-4553A, Specification for Immersion Silver Plating for Printed Boards. This newly revised specification sets the requirements for the use of immersion silver (IAg) as a surface finish for printed boards, adding a maximum deposit thickness based on performance criteria; the minimum thickness requirement was provided in the original release of IPC-4553. Revision A also establishes a single thickness range to avert confusion between what is “thin” and “thick.”

“While the maximum thickness requirement may seem like a relatively simple item to generate, it took a great deal of effort on the part of the 4-14 Plating Processes Subcommittee to define the hard number of what the maximum thickness can be to produce a high quality surface finish,” says Subcommittee Co-Chair Gerard A O'Brien, President, Solderability Testing & Solutions Inc. O’Brien notes that the lack of a maximum thickness requirement in the original release of the document in 2005, confounded with the “need to know” of whether the IAg being used was of the “thin” or “thick” variety, could easily mislead a user to apply the finish outside its optimum process window. He adds, “This, in turn, could result in an inferior finish quality that would not perform adequately during subsequent assembly.”

Addressing the misunderstandings of “thin” vs “thick,” Revision A establishes a single thickness range. As Subcommittee Co-Chair George Milad, National Accounts Manager for technology, Uyemura International Corp, explains, “What was formerly termed ‘thin’ is no longer recognized or addressed in IPC-4553A. ‘Thin’ immersion silver has declined to such a minor portion of the total immersion market that delineating two thickness ranges just exacerbated the confusion between board manufacturers and their chemical suppliers."

More information on IPC-4553A, Specification for Immersion Silver Plating for Printed Boards, is available in the IPC online bookstore at www.IPC.org/onlinestore. Questions should be directed to subcommittee staff liaison, Tom Newton, IPC Director of PCB Programs, Standards and Technology, at TomNewton@ipc.org.

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