Conformal coatings have traditionally been tested by determining the mean time to failure of conformally coated hardware exposed to corrosive test environments. This test approach has serious shortcomings: The test temperatures are most often too high. At these high temperatures, the conformal coating properties may be quite different from those at the application temperatures. In addition, the times to failure are unacceptably long extending into many months. Overcoming these shortcomings is an iNEMI championed test that involves exposing conformally coated thin films of copper and silver to sulfur vapors at 40-50 oC in flowers of sulfur (FoS) chamber and using the corrosion rates of the coated metal thin films as a measure of the corrosion protection capabilities of the conformal coatings. The test temperatures are similar to the application temperatures, the test durations are no more than a week and can be conducted under various temperature and humidity conditions. The purpose of this paper was to determine if testing in the industry-standard mixed-flowing gas corrosion chamber would give similar results as those using the FoS chamber. Acrylic, fluorinated acrylate, and atomic layer deposition conformal coatings were tested in three environments: (a) flowers of sulfur (FoS), (b) mixed-flowing gas (MFG), and (c) iodine vapor. The performance of the coatings tested in the FoS and the MFG corrosion chambers were quantitatively similar. The iodine vapor test results were in qualitative agreement with the FoS and MFG test results. In addition, we present early results pointing to the utility of terahertz-frequency imaging as a technique for measuring conformal-coating thickness nondestructively.

Flowers of sulfur testing of conformal coatings is well researched and established. However, the electronics industry has a long history of testing based on mixed-flowing gas environments. This work compares the results of testing three commonly available conformal coatings using the flowers of sulfur, the mixed flowing gas and the iodine vapor tests. Serpentine thin films of copper and silver were coated with the conformal coatings under test and the corrosion rates of the underlying thin films were measured by electrical means in the flowers of sulfur and the mixed-flowing gas environments. In the iodine vapor test the extent of thin film corrosion was visually evaluated. The extent of corrosion of the metal films was used as a measure of the conformal coating performance. The three test results were in qualitative agreement.

The field of cleaning applications related to modern semiconductor production technologies covers very different types of substrates and tasks. Modern water-based cleaning technologies such as microphase cleaning (MPC) and fast acting surfactant technology (FAST) are used in defluxing after different manufacturing processes such as wafer bumping, flip-chip assembly and die-attach used for power modules and devices. The cleaning agents to be used for Semicon Backend applications should be water based and their chemical content should have the ability to remove different kinds of fluxes and solder pastes even from difficult areas at moderate process parameters. Lastly, the cleaning agents should be compatible for various polymers and metals and should have high loading capacity or bath life.