We paint bare die electronic assemblies to create a uniform emissivity in order to perform infrared camera thermal measurements under power. Without this process, surfaces with low emissivities would appear lower in temperature than a high emissivity surface at an equivalent temperature. Can you recommend a paint for this application? It should have very low ionic content so as not to cause shorting or current leakage on the bare die and substrate surfaces? Other desirable characteristics would be stable properties at temperatures from-40—200C, availability in aerosol can form, fast drying, black color, ability to be applied in thin films and good adhesion to SiO2 die passivation layer. Thank you for any assistance you can provide. J.M.
There are aerosol cans of black paint available at paint and craft stores. You could try the flat black or ultra flat black. However, these paints are thermoplastic acrylic based and are therefore not stable at elevated temperatures and will not meet the 200C requirement. Better choices would be paints based on styrenated alkyd or styrenated epoxy resins. Paints based on both these resins will dry as fast as the acrylic lacquer, adhere well to the substrate and meet the temperature requirement.
Go to www.pfonline.com, click on “Suppliers” and then click on “Paints and Liquid Coatings.” This should give you a start on finding some companies that make the paint you are looking for. These companies can also be found in the 2000 Products Finishing Directory and Technology Guide on pages 372-375. Ask for flat black paints based on styrenated alkyd or styrenated epoxy resins to be packaged in aerosol cans. Since it is common practice to supply touch-up paints in spray cans, there should be no problem.