Laser depaneling can be executed with high precision. This will make it extremely useful in situations where parts of the board outline demand close tolerances. Additionally, it becomes appropriate when tiny boards are involved. Since the cutting path is quite narrow and can be located very precisely, PCB Depanelizer may be placed closely together on the panel.
The reduced thermal effects imply that even though a laser is involved, minimal temperature increases occur, and therefore essentially no carbonization results. Depaneling occurs without physical connection with the panel and without bending or pressing; therefore there exists less probability of component failures or future reliability issues. Finally, the location of the cutting path is software-controlled, which means modifications in boards may be handled quickly.
To check the impact of the remaining expelled material, a slot was cut in a four-up pattern on FR-4 material with a thickness of 800µm (31.5 mils). Only few particles remained and consisted of powdery epoxy and glass particles. Their size ranged from typically 10µm to a high of 20µm, and a few may have was made up of burned or carbonized material. Their size and number were extremely small, with no conduction was expected between traces and components on the board. If you have desired, an easy cleaning process might be included in remove any remaining particles. This kind of process could consist of the use of any type of wiping with a smooth dry or wet tissue, using compressed air or brushes. You can also employ just about any cleaning liquids or cleaning baths with or without ultrasound, but normally would avoid any type of additional cleaning process, especially an expensive one.
Surface resistance. After cutting a path within these test boards (slot in the middle of the test pattern), the boards were exposed to a climate test (40?C, RH=93%, no condensation) for 170 hr., and also the SIR values exceeded 10E11 Ohm, indicating no conductive material is
Cutting path location. The laser beam typically uses a galvanometer scanner (or galvo scanner) to trace the cutting path within the material spanning a small area, 50x50mm (2×2″). Using such a scanner permits the beam to become moved at a very high speed across the cutting path, in the plethora of approx. 100 to 1000mm/sec. This ensures the beam is in the same location only a very short period of time, which minimizes local heating.
A pattern recognition method is employed, which could use fiducials or some other panel or board feature to precisely discover the location where cut needs to be placed. High precision x and y movement systems are used for large movements in combination with Pneumatic PCB Depanelizer for local movements.
In these types of machines, the cutting tool is definitely the laser beam, and features a diameter of approximately 20µm. This implies the kerf cut through the laser is about 20µm wide, and the laser system can locate that cut within 25µm with respect to either panel or board fiducials or any other board feature. The boards can therefore be placed very close together in a panel. For a panel with lots of small circuit boards, additional boards can therefore be placed, leading to cost savings.
Since the laser beam could be freely and rapidly moved both in the x and y directions, cutting out irregularly shaped boards is straightforward. This contrasts with a few of the other described methods, which may be limited to straight line cuts. This becomes advantageous with flex boards, which are often very irregularly shaped and occasionally require extremely precise cuts, for instance when conductors are close together or when ZIF connectors must be eliminate . These connectors require precise cuts for both ends in the connector fingers, as the fingers are perfectly centered between the two cuts.
A prospective problem to consider is the precision from the board images on the panel. The authors have not yet found an industry standard indicating an expectation for board image precision. The nearest they may have come is “as necessary for drawing.” This challenge may be overcome with the help of more than three panel fiducials and dividing the cutting operation into smaller sections with their own area fiducials. Shows in a sample board reduce in Figure 2 that this cutline can be put precisely and closely lmuteg the board, in cases like this, next to the outside of the copper edge ring.
Even if ignoring this potential problem, the minimum space between boards on the panel could be as little as the cutting kerf plus 10 to 30µm, depending on the thickness from the panel plus the system accuracy of 25µm.
Within the area included in the galvo scanner, the beam comes straight down in the center. Even though a large collimating lens can be used, toward the edges from the area the beam includes a slight angle. Which means that depending on the height from the components near the cutting path, some shadowing might occur. As this is completely predictable, the distance some components must stay removed from the cutting path can be calculated. Alternatively, the scan area could be reduced to side step this issue.
Stress. As there is no mechanical connection with the panel during cutting, in some instances each of the depaneling can be performed after assembly and soldering. What this means is the boards become completely separated through the panel within this last process step, and there is not any need for any bending or pulling on the board. Therefore, no stress is exerted on the board, and components nearby the edge of the board usually are not subjected to damage.
Inside our tests stress measurements were performed. During mechanical depaneling an important snap was observed. This also signifies that during earlier process steps, including paste printing and component placement, the panel can maintain its full rigidity with no pallets are needed.
A typical production method is to pre-route the panel before assembly (mechanical routing, employing a ~2 to 3mm routing tool). Rigidity will then be determined by the dimensions and volume of the breakout tabs. The final depaneling step will generate even less debris, and by using this method laser cutting time is reduced.
After many tests it is remove the sidewall from the cut path can be very neat and smooth, no matter the layers inside the FR-4 boards or PCB Laser Depaneling. If the necessity for a clean cut is not really very high, as with tab cutting of any pre-routed board, the cutting speed could be increased, resulting in some discoloration .
When cutting through epoxy and glass fibers, you will find no protruding fibers or rough edges, nor exist gaps or delamination that would permit moisture ingress over time . Polyimide, as used in flex circuits, cuts well and permits for extremely clean cuts, as observed in Figure 3 and then in the electron microscope picture.
As noted, it really is essential to keep your material to be cut through the laser as flat as possible for optimum cutting. In certain instances, as with cutting flex circuits, it can be as simple as placing the flex on a downdraft honeycomb or perhaps an open cell foam plastic sheet. For circuit boards it might be harder, particularly for boards with components on both sides. In those instances it still may be desirable to make a fixture that will accommodate odd shapes and components.