Stencil Design for Lead-Free SMT Assembly


March 5, 2018


Chrys Shea


In order to comply with RoHS and WEEE directives, many circuit assemblers are transitioning some or all of their soldering processes from tin-lead to lead-free within the upcoming year. There are no drop-in replacement alloys for tin-lead solder, which is driving a fundamental technology change. This change is forcing manufacturers to take a closer look at everything associated with the assembly process: board and component materials, logistics and materials management, solder alloys and processing chemistries, and even soldering methods.

Do not expect a dramatic change in soldering behavior when moving to lead-free solders. The melting points of the alloys are higher, but at molten temperatures the different alloys show similar behaviors in a number of respects. Expect subtler changes, especially near the edges of a process window that is assumed based on tin-lead experience rather than defined through lead-free experimentation. These small changes, many of them yet to be identified and understood, will manifest themselves with lower assembly yields. The key to keeping yields up during the transition to lead-free is quickly learning what and where the subtle distinctions are, and tuning the process to accommodate them....

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Company Information:

Cookson Electronics

Leading materials science company that provides high performance materials, chemistry and technology solutions to the electronics and surface finishing industries worldwide.

Providence, Rhode Island, USA

Manufacturer of Assembly Material

  • Phone (401) 228.8800

Cookson Electronics website

Company Postings:

(4) products in the catalog

(7) technical library articles

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