Handbook encapsulates a wealth of information on protective coatings

IPC-HDBK-850 delves into a new area, potting and encapsulants. The 88-page guideline is described as a cookbook for potting and encapsulants.

Whether they're protecting handheld products from moisture and the shock of drops or trying to improve the lifetimes of high reliability circuit boards, more design and manufacturing teams are potting and encapsulating boards. As spacing dimensions shrink, it's becoming increasingly more important to pick the right materials to protect these boards in operating environments in which a conformal coating will not do the job.

Many engineers pick these materials without much due diligence, using materials on price or simply sticking with solutions that have proven effective in the past. IPC has stepped in to provide the guidance that will help users make more effective decisions. IPC-HDBK-850, Guidelines for Design, Selection and Application of Potting Materials and Encapsulation Processes Used for Electronics Printed Circuit Board Assembly, provides a wealth of information that hasn't previously been easy to find.

"Nobody has addressed these materials before," said Barry Ritchie of Dow Corning Corp., who chairs the IPC Potting and Encapsulation Task Group. "As circuit technology gets smaller, with technologies like fine pitch and chip on board, conductors are so close that any moisture can cause a failure. Reliability requirements are also changing for many types of products like portables and in high reliability fields like aircraft, military, consumer and automotive technologies."

The handbook covers a broad range of protective materials for printed circuit boards. Traits and performance parameters are provided for conformal coatings and potting materials.

For example, it details the wide operating temperature range for silicones. It also describes benefits and detractions for polyurethanes, acrylics and epoxies. Ritchie calls the document a "cookbook" for potting and encapsulants.

"It goes from start to finish, explaining the various chemistries, detailing the electrical and mechanical properties of each type, directing people to other documents that apply," he said.

IPC-HDBK-850 includes information on choosing, mixing, applying and dispensing for each of the materials, as well as explaining the techniques that should be used when repairs are necessary.

"There's a large section on design considerations for people who want to use potting and encapsulants," Ritchie said.

He noted that although the handbook has a wealth of in-depth information, it is written for those who haven't previously given much thought to protective materials. The 88-page document includes a number of pictures that will help designers and manufacturing personnel understand the intricacies of these materials.

The genesis of the standard began a couple years ago when members of the Cleaning and Coating Committee asked why there weren't any documents for encapsulants. Once volunteers and IPC managers determined there was a need, a number of experts worked for nearly two years to complete the guidebook. Ritchie noted that that's a pretty short timeframe for a new document.

Although product developers have used these protective materials for years without a specification or handbook, Ritchie said that having a reference guide will save designers and manufacturing personnel plenty of time in the future.

"This is something that should have been done 10 years ago. It would have made my life a lot easier if this had been done in the '90s. I spent a lot of time researching information that's now all located in one place," he said. "A special thanks to all the Task Group members who participated in this handbook from the wide variety of various organizations that compiled all this information so users have a place to go and a comprehensive guide to reference."