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Before we look at conformal coating in the 21st Century, it is worth looking at how our industry has changed since the 20th Century and the effect these changes have had on reliability. 

30 years ago, we had:

• Through-hole PCAs with axial components and wide conductor spacing (see fig. 1)
• Round axial components that were easy to conformably coat
• Wide conductor spacing (causing a few problems with dendritic growth)
• Leaded solder
• The widely adopted practice of cleaning before conformal coating

Fig. 1

Now move forward 30 years. In that time, surface mount components have been developed that are predominantly square with sharp edges, conductor spacing has been reduced, and packing densities have increased to levels never dreamt of in the past (see fig. 2). 

We at HumiSeal are no strangers to conformal coatings; and if you’re reading our blogs, it’s likely you’re familiar with these coatings as well. The word “conformal” is descriptive of the function of the coatings which are expected to spread and conform evenly across all surfaces that are to be protected. This uniform and even distribution is necessary to protect delicate electronic components from things such as humidity, water, vibrations, and thermal damage (to name a few).