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Coursen Coating Labs Presents A Superior Solderable Coating MIL-C675C Compliant
Dan Coursen • Mar 12, 2019
Coursen Coating Labs has been quietly working in the shadows for over 25 years to provide alternative to gold solderable coatings. Night vision optical systems, guidance systems, endoscopy, and other industries all use our 3LPT coating. Our proprietary coating excels when used to create hermetic seals for optical housings. This solderable coating is resistant to environmental changes and displays superior adhesion to most substrates, from glass to ceramics, as it is less susceptible to thermal expansion.
We developed our 3LPT coating as a solution to our customers’ problems. One example featured a customer attempting to bond miniature optical components to ceramic using a high-grade epoxy. The epoxy would break down with exposure to radiation, causing the optics to come loose or move out of alignment. Our 3LPT coating was used to replace the joints (Figure 1), resulting in no broken bonds with the ceramic when soldered correctly. The soldered joint often outlasted the actual components.
Another client, using a Ti/Ni/Au coating on Zinc Selenide (ZnSe) windows, experienced approximately a 25% acceptable yield. The solder would often dissolve through the gold exposing the nickel layer to which the solder would not adhere. Sometimes their gold coating completely failed to adhere to the ZnSe. Additionally, the mechanical stresses of thermal expansion would sometimes cause the optical component to fail or the coating to de-laminate. We developed our 3LPT coating to remedy these difficulties. Our proprietary three-layer coating distributes the stresses of thermal expansion, preventing the coating from damaging the optic due to mechanical strain. Platinum is used for the top layer as it doesn’t amalgamate quickly in solder. We have experienced an acceptable yield above 97%. Some of the parts soldered were used in very high-stress applications consisting of rapid altitude and temperature changes with no joint failures and are still in use years later.
Our 3LPT process is superior to any gold solderable coating. Gold coatings need to be very thick, anywhere from 3-10 microns, as the gold dissolves quickly in solder, whereas the 3LPT coating is usually between 0.5 and 1 micron. It is a low-temperature process (below 200º C), making it acceptable for use with more delicate parts and electronics. The exceptional yield and durability mitigate costly repairs to solder joints. 3LPT has undergone extensive stress analysis, including solder pot immersion and cryogenic testing, with little to no effect on the solderable coating and meets MILSPEC-C675C environmental standards. There is no long-term embrittlement with 3LPT as there is when using gold, and many of the parts we coated 20 years ago are still in use today. This coating is suitable for most types of
glass, ceramics, and exotic substrates such as Zinc Selenide, Germanium, Zinc Sulfide, Sapphire, and Magnesium Fluoride, to name a few.
Dan Coursen, the President and CEO of Coursen Coating Labs, states, “This coating was developed to replace coatings that failed to maintain integrity during extreme environmental stress. The customers using the 3LPT coating have been very impressed with our product and have not been able to find another coating as robust or durable to accomplish the same task. Gold just doesn’t cut it for some applications.” You can read about our case studies on 3LPT at this link: https://www.coursencoating.com/solderable-coatings. Our customers include top aerospace/defense companies and the medical industry.
Coursen Coating Labs, Inc. is a small family-owned business in Southern California. We have been in business under various names since 1967 and take great pride in helping our customers achieve their goals. My father worked at this plant since the early '70s and, in 2009, purchased the company. I took over from him in 2016 to continue to supply our customers with first-rate products and services. We are ITAR registered and able to accept government contracts or sub-contracts. Give us a call or visit our site to see all we have to offer. We look forward to hearing from you.