RoHs and Immersion Silver Frequently Asked Questions

• Why choose silver immersion over other RoHS-compliant options?

  We are convinced that immersion silver is the best RoHS compliant finish for the majority of our customers and their applications. Our testing has shown that silver gives the best solder joint of any of the other finishes tested.

  Silver immersion plating has been on the market for 10 years and end user benefits from this finish long before RoHS requirements came into play. Silver, when stored properly, has a shelf life of 12 months (easily as long as OSP), and can withstand multiple heat cycles during assembly. Silver immersion does not require any special fluxes or solders and fits in perfectly with the “quick turn” mode of operation.

  The contact resistance is very low (see chart) and the co-planarity of the finish provides a completely flat surface for solder paste application on fine pitch devices. The silver immersion finish is easily electrical tested without damage or “puncture” of the surface of the silver plating.

  We have found that the Immersion Silver plating process is not limited to just a “post mask” finish, but can be applied to boards prior to mask and can also be processed through nickel/gold tab operations without any adhesion complications. When we process an Immersion Silver plating order, we not only give our customers the best finish (in our opinion) but, for complete RoHS compliance and assembly needs, we put this finish on high Tg, high Td and low CTE material; all at no extra cost.

• Do our RoHS boards cost more?

  Sunstone offers flexibility for you to choose your board finish, our immersion silver plating is available with all our services at NO ADDITIONAL COST.

• What are the temperature requirements for lead-free processing (material, etc)?

  The temperature is dependent on the soldering profile of the lead free solder used. This is usually about 30 °C higher than standard tin/lead solder (peak temperatures of 250 °C opposed to 220 °C for tin/lead). The material we use for our RoHS compliance boards are built to withstand these higher temperatures. Solderability of silver immersion boards (Can I use lead solder on silver boards and what temperature needs to be used) Our RoHS compliant silver immersion finished boards can be soldered with standard tin/lead solder at standard tin/lead temperatures or using RoHS compliant solder at the higher no lead soldering temperatures.

• What is the thickness of Immersion Silver plating?

  4 – 12 micro inches.

• Is the board performance affected with RoHS processing?

  Although we cannot address new RoHS compliant components, the characteristics of the material used in building the RoHS compliant laminate do not vary significantly from laminate that is less temperature resistant; therefore we would not expect a significant change in the performance of the board.

• What is the purity of the silver immersion we use?

  The purity of silver is 90%+

• How do I order RoHS boards?

  On our web site, choose silver finish instead of tin/lead and we will automatically build those boards on high temperature resistant RoHS compliant.

• What is the shelf life of our Immersion Silver RoHS boards?

  If the wrapped packages are stored at less than 35 °C and 85% R.H. then there is a shelf life of 12 months. If boards are unpackaged and unused, then they should be re-packaged.

• Do we have UL approved RoHS boards?

  Yes

• What are our material thickness limitations?

  0.062 standard thickness for all board orders, including Quickturn PCB Prototype boards. For Full Feature printed circuit board design orders other than 0.062”, please call for availability.

• Can I make multi-layer RoHS boards?

  Yes, check out our multilayer PCB design support page.