In the majority of flex PCB designs the coverlayer or covercoat serves more than one purpose. For example, covercoats typically do as solder masks, aiding to avoid solder from shorting circuit traces together, but additionally serve to electrically isolate and physically safeguard the circuit from damages.

Coverlayers help to literally limit the pads as well as hold them in place during soldering, preventing pad lift. The coverlayer (or possibly a covercoat) likewise enables conductors to be positioned in the neutral axis for enhanced flex as well as flexing efficiency.
Offered the variety of parts flex circuits play in electronic product packaging, it is easy to understand that it has actually been hard for suppliers ahead up with a global option that is low-priced, high-performing and very easy to apply. Nonetheless, stable progress is being made by product distributors and new solutions are being created as well as supplied to the market.

There are numerous sorts of flexible covercoating systems available, each with its very own unique applications and benefits. Included amongst them are the following:

ADHESIVE-BACKED FILMS

Adhesive-backed polymer films are the type of coverlayer most frequently defined and also utilized by flex circuit developers and manufacturers. It is also the flex circuit covering method best suited to vibrant flex circuit applications due to the balanced material homes back and forth.

SCREEN PRINTABLE LIQUID COVERCOATS

Applied as well as treated by straightforward ways, display liquid covercoats are the least expensive covercoat kind and also the type most often used with polymer thick film as well as easy singlesided copper constructions.

PHOTO-IMAGEABLE LIQUID AND FILM POLYMERS

Newer methods for covercoating flex circuits include the use of photo-imageable polymers. The outcomes have actually been extremely promising. In process, the flex circuit is coated with a polymer movie, which could after that be imaged and created to accessibility discontinuation attributes. This method, which looks fairly helpful for numerous applications, can put an end to a lot of the coverlayer misregistration problems manufacturers have actually had with little features and can also vanquish issues over glue squeezeout onto lands.

SIZING COVERLAYER OPENINGS

The sizing of coverlayer openings differs according to pad design attributes as well as the number of steel layers. The crucial location of issue is with single steel layer flex circuits, where issues over possible pad lift need special care in design. It gives general standards for sizing of coverlayer openings.

MAP TO CUT LINE CONCERNS

Best present technique for flex circuit design usually advises that the edge of the part to the side of conductor spacing be > 1.25 mm (0.050″). It has been revealed that circuits can be made reliably with edge to conductor spacing of 250µm (0.010″), however this generally boosts the expense which differs depending upon the tooling system used.