Follow electronics technology development,many PCBs outline became more and more complexity. New products on market require PCB outline with high accurate,also appearance is criticized.it’s difficult for traditional outline manufacture. As Laser machining have advantages like high accurate,high speed,low cost.more and more PCB manufacturers start to purchase laser equipment to solve this situation.
CO2 laser working theory
CO2 Laser used in PCB manufacture is 10.6um wavelength with high power impulse laser, it has strong ability in cutting.now CO2 laser widely used in blind via drilling,FPC outline and laser target.
Laser drilling for blind vias
Laser cut coverlay
You can see most of CO2 laser used in thin board manufacture at present.Evoke us rethink if CO2 laser can used in other manufacture range. How to expand its application to achievement from dot to line to plane? It became a major topic of common thinking in electronic industry.
CO2 laser principle of work and analysis
CO2 laser work is dot matrix from dot to line.when the space between dot and next is enough small,laser appears smooth cutting like below：
look at the front horizontal of laser cutting:
Actual picture of look at the front horizontal of laser cutting
Overhead view of laser cutting
Actual picture of Overhead view of laser cutting
As laser cutting focal distance is limited,laser power will reduce follow the depth increase, like v-cut theory. As laser beam is small,so the cutting edge is small,the cross-section like below:
cross-section sketch:
The actual cross-section picture:
CO2 Laser plane cutting principle and analysis:
Laser plane connects 3 dimension,dot-matrix picture is 2 dimension, and laser power decide the 3rd dimension. Dot- matrix design follow beam dimension to calculate,overspread whole panel,can meet different depth of cutting.
Doc-matrix cutting,it will appears micro-pit.we need adjust the laser power,make the depth of cutting don’t effect by micro-pit, it almost smooth in appearance.
CO2 laser fabrication application and technology development
PCB material of laser cutting effect analysis
CO2 laser always used in nonmetal material,as the absorbance of laser is high to nonmetal materials.we analyse several common materials of resin+ glass epoxy,PTEE+glass+ceramics filler’s laser cutting effects and study laser cutting quality and manufacture control.we study from three aspects, the first aspect is laser manufacture productivity,same parameters data to compare. The second aspect is manufacture homogeneity, the highest deviation to compare. The third aspect is appearance quality,if serious carbonize after fabrication. Below is the data of comparison.
Form above manufacture results,we can see PTFE+glass it easy to laser manufacture. The highest deviation is less 0.1mm,means laser cutting can meet the outline tolerance. Resin+epoxy glass is easy carbonize in appearance,glass+ceramics is also have sligh carbonize,but PTFE+glass didn’t be carbonized.we should control this kind of carbonized problem if appearance is critical.
CO2 laser manufacture technology and development
We use laser to cut the PI coverlay and FPC outline in general. Actually laser also can use in rigid PCB,and have strong control for depth milling,so laser have big space in different material cutting.
(a.)Flex-Rigid PCB laser cutting technology
Flex-rigid PCB use V-CUT to cut the cover.Actually laser also adapt in cover cutting.it have strong control for the depth.
Compare traditional v-cut manufacture,laser can meet small depth v-cut. Common v-cut machine is limited board thickness and hardness, it’s hard manufacture small depth v-cut and thin board.
laser cutting don’t need two sides cutting,it can from one side cut to bottom side and don’t need enlarge.
Mechanical V-CUT from two sides:
Laser V-CUT from one side:
(b.) PTFE laser cutting
PTFE outline routing have more burrs use mechanical milling,rework consume much time.but no burrs if use laser routing.
But the PTFE material is more thick than PI, it over the focal distance range. So we need routing the outline from top and bottom sides.
Mechanical routing
Laser routing
CO2 Laser plane manufacture and application
(a.) PCB material’s laser plane manufacture study
Like above from different aspects to study: laser plane manufacture productivity, homogeneity and appearance.
From above results,we can see PTFE+glass’s manufacture productivity is the best.the highest deviation of homogeneity is less than 0.1mm,plane manufacture of laser can meet the tolerance.Resin epoxy+glass have serious carbonized in appearance,others don’t have this kind of problem.
(b.)Laser plane manufacture can used to rework of solder mask opening.
Sometimes board missed one pad solder mask opening after finished board,at last we had to scrap the PCB. Actually,laser machine can solve this problem so easy. Use laser make depth milling can rework the mistake very soon.
Below a pad missed solder mask opening
After laser milling
(c.) Laser depth routing technology
Depth routing manufacture is hard to control for lamination press thickness tolerance,glue overflow,accurate of mechanical routing problems. But use laser milling, it’s excellent of accurate and no other difficults.
