For the past 40 years, standard mechanical PCB milling systems have been the tools of choice for straightforward milling operations, and in some cases, they’ve been great performers for flex PCB etching as well. LPKF’s top-performing ProtoMat mechanical PCB milling systems, for example, feature faster spindle speeds, low runout and high resolution for working with substrates as thin as 5 mil for single-sided designs and traces, and spacing as small as 4 mil. All good stuff, so how could it get even better? Laser.
Today, laser machines have taken flex PCB prototyping to a higher level to give manufacturers more precision and cost savings. The high positional accuracy and depth-of-cut calibration possible with lasers can handle the most challenging applications on some of the most difficult flexible materials. In addition, because PCB designers can perform laser etching with a compact, in-house laser, they avoid the high cost and turnaround time required when outsourcing to a board house. Surprisingly though, lasers are the unsung hero of the PCB world. Laser removal of metal from flex materials is a very unique process, but not many manufacturers have tried it. Here are some good reasons why they should:
•With a 20um diameter focused laser beam, even smaller traces and spacing are possible depending on the material.
•Au removal and additional metal ablation can also be achieved on various PET materials.
•Microvia drilling of flex polyimide materials can also be completed with the same laser creating 50um (2 mil) diameter vias.
•Polyimide stencil cutting is also a standard capability of the LPKF UV laser models.
•Partial laser engraving of polyimide is also possible with the laser power, travel speed and pulse frequency adjustable as laser tool settings.
Our ProtoLaser systems play a leading role in flex PCB laser etching at LPKF. We’ve developed a hatch and controlled laser delamination process that enables our ProtoLaser to create double-sided designs by removing copper to achieve ~3 mil (75um) traces on DuPont Pyralux® TK 127512R fluoropolymer/polyimide composite and Pyralux® AP 8565R polyimide materials. Copper ablation is also possible on DuPont Pyralux® TK or with AKAFLEX KCL 9-25 from the Krempel Group since laser energy is absorbed at the adhesive layer.
The bottom line is that flexible PCB materials and circuits are playing an increasingly more important role in today’s PCB industry. This demands more precision and accuracy in etching highly complex flexible cicuits. While mechanical milling machines still have their place, the laser systems give you the added advantages of precise energy control, minimal stress, arbitrary contour cuts, and more accurate, dynamic positioning for the smallest flexible circuit etching.