In the majority of flex PCB designs the coverlayer or covercoat offers greater than one objective. For instance, covercoats generally do as solder masks, helping to stop solder from shorting circuit traces with each other, yet likewise serve to electrically isolate as well as literally safeguard the circuit from damages.
Coverlayers help to literally limit the pads as well as hold them in place during soldering, avoiding pad lift. The coverlayer (or potentially a covercoat) also enables conductors to be placed in the neutral axis for boosted flex and bending efficiency.
Given the diversity of duties flex PCB play in electronic packing, it is easy to understand that it has actually been hard for distributors to come up with a global solution that is low-priced, high-performing and also simple to use. However, stable development is being made by material distributors and brand-new options are being developed and provided to the industry.
There are a number of sorts of flexible covercoating systems available, each with its very own unique applications as well as benefits. Consisted of among them are the following:
ADHESIVE-BACKED FILMS
Adhesive-backed polymer films are the kind of coverlayer most frequently defined as well as used by flex circuit designers and manufacturers. It is additionally the flex circuit covering method best suited to dynamic flex PCB applications due to the well balanced product properties back and forth.
SCREEN PRINTABLE LIQUID COVERCOATS
Applied as well as healed by easy means, screen liquid covercoats are the least expensive covercoat type and the kind most often made use of with polymer thick film as well as basic singlesided copper constructions.
PHOTO-IMAGEABLE LIQUID AND FILM POLYMERS
Newer methods for covercoating flex PCB include using photo-imageable polymers. The results have actually been really appealing. In process, the flex circuit is covered with a polymer film, which can then be imaged and also established to accessibility discontinuation attributes. This method, which looks fairly great for many applications, could put an end to many of the coverlayer misregistration troubles manufacturers have had with small features as well as can also vanquish problems over glue squeezeout onto lands.
SIZING COVERLAYER OPENINGS
The sizing of coverlayer openings varies according to pad design features as well as the variety of steel layers. The essential location of problem is with solitary steel layer flex circuits, where concerns over feasible pad lift need unique treatment in design. It supplies basic standards for sizing of coverlayer openings.
MAP TO CUT LINE CONCERNS
Ideal current technique for flex circuit design usually recommends that the side of the part to the side of conductor spacing be > 1.25 mm (0.050″). It has been shown that circuits can be made accurately with side to conductor spacing of 250µm (0.010″), but this generally enhances the price which differs relying on the tooling system made use of.