While single-metal layer flex PCB circuits are extensively utilized, two conductor layer (likewise described as double-sided and two-metal) flex PCB are becoming more prominent as packaging thickness increase. Two-metal layer flex building and constructions are very popular in a wide range of applications from cameras and mobile cellphones to medical tools and IC packaging. Like singlesided flex PCB, there are a number of different means that can be utilized to create double-sided flex circuits. Two-metal layer flex circuits are not as effortlessly adjusted to roll-to-roll handling as single-sided flex PCB. Double-sided flex PCB circuits can be produced in a roll-to-roll fashion. The following are descriptions of techniques for creating double-sided flex PCB that have actually been utilized in the past, are currently in use or are under research study for future use.

PANEL PLATE PROCESS

Panel plating of flex PCB circuits is a long-standing method as well as, like various other processing approaches, it has advantages and downsides relying on a variety of different variables. From a processing point of view, it is easier to electroplate a non-patterned panel. Nonetheless, the additional thickness works against the cause of versatility and also makes fine function definition harder. A typical manufacturing sequence for this procedure is as adheres to:

– Metal clad laminate is drilled with the wanted opening pattern.
– Hole wall surface surfaces are made conductive using an electroless copper procedure or an ideal choice, such as a graphite layer offered by OMG.
– Laminate is electroplated with copper to build the copper plating thickness in the red to meet requirements.
– Dry movie withstand is applied to the laminate on both sides.
– Circuit image is patterned into the steel outfitted and plated-through laminate, ensuring that, after development, the through-holes are tented dependably to shield against the etching process.
– Resist-patterned attired laminates are etched to create flex circuit patterns on both sides.
– Resist is removed and coverlayers are laminated flooring to the top as well as lower as needed.

Except for the plated through-hole section of the process, the treatment is nearly identical to the treatment made use of for the manufacture of single-sided flex PCB. The flow sheet gives greater information about the circuit processing actions.

PATTERN PLATE PROCESS

Pattern plating is an usual variant utilized to produce twometal flex PCB circuits with layered through-holes.

– Negative picture of the flex PCB circuit pattern is produced, which reveals through-holes for layering in addition to the conductors.
– Copper circuit is overplated with an etch chemistryresistant metal such as tin, solder, gold or others. These metals will protect the circuit pattern as well as through-holes throughout the etching process depending on the sort of chemistry made use of.
– Plating withstand is stripped.
– Circuit is engraved using an etchant that does not attack protective metal down payments. Ammonia-based or sulfuric acid-peroxide etchants are both generally made use of as they preferentially attack copper.
– Protective metal is stripped from the flex PCB circuit leaving a bare copper circuit similar to the one produced by panel plating.

The best benefit of the pattern plating process is recognized when functions are great, little annular ring exists in the danger and also a design is high of the withstand being undercut as well as etching out the copper from layered through-holes. This technique is also of value when better circuit functions are needed due to the fact that a smaller sized amount of copper has to be etched though to develop the flex PCB circuit photo. The outcome is a decrease in diminishing and also a more exact final circuit pattern.