Under Pressure: The Sticky Business of Laminating High Performance Multilayer Boards

Bummer! Now, I’m going have Freddy Mercury camped in my head all day singing “Un-dah Presh-ah.”  Well, let me see if I can drown him out with discussing the Wonderful World of PCB Lamination. Even I want to run screaming from my own brain after contemplating this topic for very long!

Many times as I have thought about the various challenges of manufacturing High performance boards, my mind is helplessly drawn to make a comparison to bread making. When you think about it—they are both born from chemically based processes and formulas, right? Okay, maybe I need to cut down on the Food channel, but stick with me anyway!  For instance, there is grocery store bread that is mixed in towering vats, and baked in loaves by thousands, and then there is Artisan bread. Mmm…that warm, wonderful, crusty bread, that is made in small batches by passionate bread makers.You know the ones; they waft with the tangy fragrance of things like fresh rosemary or garlic. These breads often boast of secret recipes.  Some areas of Italy have famous breads, whose bakers claim that it is the water, unique to that region that makes it special.

Regardless, both types of bread have value and a place in our lives.

In my visually, and apparently culinary driven mind it goes like this:

FR-4 boards = Wonder Bread 
RF/MW/High performance boards = Artisan Bread

With this in mind, let’s consider multilayer designs that include high performance materials—either on all layers or on selective layers.  What is required for successful production of these boards?  Once again, we need material gurus who are fluent in the knowledge of high performance materials and how they behave.  In this case, specifically, how they respond to lamination; because, as I’ve said many times, they all act uniquely.  Each high performance material comes with its own lamination profile, a recipe of sorts, which specifies the temperature rise rate, as well as the cooling rate.  These are provided to us by the material manufacturers, however, this recipe must be “tweaked” for the Press being used, and the environment in which it is being produced.  In other words—we are back to that intangible, though critical aspect of Art and Magic—like Artisan bread making!

A second concern, during lamination is the surface treatment of the layers.   All boards must be cleaned thoroughly and put through a scrubber prior to lamination.  This ensures that the surface is free of all contaminants and debris that would prevent strong, even adhesion or create de-lamination in the future.  High performance boards require special TLC at this stage of fabrication.  They cannot be treated like standard boards due to the material composition.  A little known secret, at this stage of fab,  makes all the difference—but if I told you what it was, I would have to kill you.  (Sorry, it’s part of our secret recipe!)

When standard multilayer boards are made they are “booked” by stacking the layers together with pre-preg placed between each layer to act as a bonding medium (epoxy-resin loaded fiberglass sheets).  When you have varying substrates on various layers, that formula goes out the window.  Farewell, Wonder bread.   Every high performing material has a corresponding bond ply that matches its properties in order to bond properly and also for performance reasons.  This information is supplied by the material manufacturers as well. It is critical that a RF/MW/High performance board manufacturer be current and well-versed on bond plies. Hello Artisan bread.

The last item of interest, when it comes to lamination, is the impact of the environment on High Performance materials. All substrates are somewhat impacted by humidity, this is especially true in some types of High Performance substrates.  They are very vulnerable to humidity and the environment. Awareness of which materials are most vulnerable and how to treat them are crucial to success.

It all comes down to this:  Only Master Bakers make Artisan Bread! Artisan bread makers are able bake Wonder bread, but beware of the baker who makes Wonder bread everyday and tells you he can make you a great loaf of Artisan bread!

Master Board makers successfully and consistently make RF/MW and High Performance boards because they have the knowledge, skill, experience and all the secret recipes that make for a top-notch high performance product. Therefore look for the qualities of a “Master” when you evaluate potential suppliers.  It will save you much time, frustration and headache if you do.

Bon appétit!

–Judy Warner