PCB Fabrication

Surface Finish

by:A-TECH      2020-10-27

Pb-free sizzling air solder level finish continues to achieve momentum as a viable floor end possibility. Although SnPb HASL was the most typical surface end prior to RoHS, Pb-free HASL wasn’t given serious consideration when the transition to Pb-free occurred. There was concern with end planarity, copper dissolution, and heat harm to the circuit boards. These points have since been largely overcome when solder alloys such as SnCuNi, SnAgCuNi or SnCuCo have been employed.

The floor end influences the process yield, the quantity of rework essential, the field failure fee, the power to test, and of course the fee. One can be lead astray by selecting the lowest value surface finish solely to search out that the total price is far higher. The choice of a surface finish must be done with a holistic approach that considers all essential aspects of the assembly. This paper will weigh the attributes of the assorted finishes and make suggestions of which fits finest with numerous product purposes. In situations the place there isn't a clear match, numerous engineering tradeoffs may be made.

The number of the floor finish to be used on the PCB could be the most important materials decision made for the digital assembly. These embody ImAg, OSP, ENIG, ImSn together with some newer choices to be mentioned.

Since galvanic interaction with Cu helped drive copper sulfide creep corrosion within the presence of ImAg, it's potential the same might occur with EPd . The Pd finish would have all the benefits of silver , however wouldn't tarnish. This could be a beautiful finish for a lot of applications and is summarized in Figure 14.

The nickel is corroded under the gold inflicting the surface to be brittle and to separate underneath meeting processing. This will result in cracked or failed solder joints that aren't repairable and infrequently discovered too late, costing the industry hundreds of thousands in PCBs and components. The gold and palladium layers are inert and don't oxidize, leading to glorious shelf life.

Electroless Nickel Immersion Gold is a two-layer coating on the copper floor of a printed circuit board. The development and significance of the RoHS regulations seem to have popularized ENIG to become one of the used finishes, particularly across the PCB trade. Selecting the proper floor end in your printed circuit boards is as important as discovering a manufacturer to supply the PCB. Using an incorrect surface finish may see you going through downstream points in relation to assembly or reliability points.

Contact us at present with questions about immersion gold and gold plating, or inquire about a free quote on circuit boards or other initiatives. A water-based mostly, natural surface finish, natural solderability preservative is an environmentally friendly option that requires low equipment upkeep. The end locations selective bonds to the uncovered copper, often utilizing a conveyorized course of, and offers an organometallic layer that protects the copper earlier than soldering.

Once the gold and palladium are dissolved in the course of the soldering process the remaining layer of nickel prevents copper leaching into the solder. At SPC, we offer high-high quality metallic plating and ending providers, including exhausting plating and ENIG plating.

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