How will the heat generated by a laser beam affect my board and components during depaneling? Will it melt edge components into an ugly heap? Or demolish thin flex materials into an unrecognizable blob? We get these worst case scenario questions all the time from PCB designers and manufacturers who have relied on mechanical routers, manual cutters, and other traditional depaneling machines throughout their careers. So it is no wonder that there’s an ongoing concern about a laser’s heat affective zone (HAZ), and the thermal effect on edge components in particular.
Flexibility is a good thing if you’re an Olympic gymnast or Cirque du Soleil performer – and it’s essential for PCB designers and manufacturers whose prototypes and end products demand precision etching on flex PCB materials. 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.
It seems like there are more myths about UV laser depaneling than there are about the Loch Ness Monster. But unlike old Nessie, UV laser depaneling myths are much easier to debunk.
“What’s that discoloration on the edges?”
That’s the question asked most often with an element of shock and surprise by people who are using UV laser depaneling machines for the first time to cut PCBs from FR4 and polyimide. The simple answer is that some edge charring occurs on thicker materials like FR4 and the “discoloration” is a carbon residue produced on each pass of the laser. In most cases, the edge charring is just a cosmetic issue that does not affect PCB quality. The biggest concern is that the carbon dust may be conductive and may somehow contaminate or short-circuit components populating the board.
Putting together an automated SMT assembly line is like building a sports team. You’re looking for the best available player at each position and those you can count on to deliver the highest level of performance week in, week out. But like the kid with untapped talent who sits on the bench game after game, UV laser depaneling is often overlooked as a key component of the SMT assembly line.