Haze and lack of clarity are considered among the most vexing and stubborn of defects in the assembly of LCD screens and surfaces. Significant advances have been made in the optical quality and capability of liquid crystals and LEDs; however, these advances can be stunted by choices made further along in the assembly process. Specifically, liquid optically clear adhesives (LOCAs) used in the bonding of assembly layers can cause haze and light refraction either immediately or under certain aging conditions. The proper design of LOCA materials must take this risk of haze development into consideration. There are a number of effective approaches to minimizing or eliminating haze.
Take a quick look at the photograph on your right. If you are in the business of PCB manufacturing with conformal coatings, does it frighten or concern you at all? Does the magnified coating appear to truly “conform” to the surfaces evenly? And if not, what effect, if any, might this have on the protection of your PCBs?
First of all, don’t panic. What you see in the photograph is not unusual and is not necessarily a problem. It is important, however, that if you are in the business of applying conformal coatings, you should have a clear understanding of some of the unique challenges they present.
Encapsulant solutions are commonly used to enhance protection of circuit boards from environmental and liquid contaminants, chemical attack, and electrical shortages. While potting materials provide many positive attributes when used to protect PCBs, sometimes other issues arise during and post application of these compounds. This blog focuses on “bubbles” forming within the encapsulant itself.
When conventional coating methods such as hand spray, total dipping or robotic selective coating don’t provide the protection required, there is always selective dip coating.
What is selective dip conformal coating?
Selective dip coating is a process whereby the substrate rather than globally immerised in the coating, is discreetly coated in desired locales. The technique in one form or another, has been around for over 25 years and is used with both classic solvent-based coatings and 100% UV cure conformal coatings.
Have you ever seen your conformal coating separate or de-wet? Have you observed the conformal coating to flake off after cure? The key to your success is understanding the relationship between surface energy (of the substrate) and surface tension (of the conformal coating). There are some simple steps you can take to help ensure you possess a healthy balance of both.
This blog post outlines the techniques required for the removal of HumiSeal UV cure conformal coating. The products covered in this article are:
- UV40, UV40-250
- UV500, UV500LV
There are 3 methods for the removal of HumiSeal UV conformal coatings:
- Mechanical removal: Powder Micro Abrasion
- Thermal removal: Burn Through
- Chemical removal
All three methods will effectively remove the coating, depending on the process requirements, to allow individual component replacement and subsequent re-coating.