Laser depaneling can be executed with high precision. This will make it extremely beneficial in situations where areas of the board outline demand close tolerances. It also becomes appropriate when tiny boards are participating. Because the cutting path is very narrow and can be located very precisely, PCB Depanelizer can be put closely together on the panel.
The reduced thermal effects suggest that despite the fact that a laser is involved, minimal temperature increases occur, and thus essentially no carbonization results. Depaneling occurs without physical connection with the panel and without bending or pressing; therefore there is certainly less probability of component failures or future reliability issues. Finally, the positioning of the cutting path is software-controlled, meaning modifications in boards can be handled quickly.
To test the impact of any remaining expelled material, a slot was cut in a four-up pattern on FR-4 material using a thickness of 800µm (31.5 mils). Only few particles remained and was made up of powdery epoxy and glass particles. Their size ranged from typically 10µm to a high of 20µm, and a few might have was comprised of burned or carbonized material. Their size and number were extremely small, and no conduction was expected between traces and components on the board. In that case desired, an easy cleaning process may be included in remove any remaining particles. This kind of process could contain the usage of just about any wiping with a smooth dry or wet tissue, using compressed air or brushes. You can also have just about any cleaning liquids or cleaning baths with or without ultrasound, but normally would avoid any type of additional cleaning process, especially a costly one.
Surface resistance. After cutting a path in these test boards (slot in the center 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 utilizes a galvanometer scanner (or galvo scanner) to trace the cutting path in the material over a small area, 50x50mm (2×2″). Using such a scanner permits the beam to be moved with a very high speed over the cutting path, in the range of approx. 100 to 1000mm/sec. This ensures the beam is incorporated in the same location only a very short period of time, which minimizes local heating.
A pattern recognition method is employed, which can use fiducials or any other panel or board feature to precisely find the location where cut must be placed. High precision x and y movement systems can be used as large movements in combination with Motorized PCB Depanelizer for local movements.
In these kinds of machines, the cutting tool is definitely the laser beam, and it has a diameter of approximately 20µm. This means the kerf cut from the laser is all about 20µm wide, as well as the laser system can locate that cut within 25µm regarding either panel or board fiducials or any other board feature. The boards can therefore be placed very close together in a panel. For any panel with lots of small circuit boards, additional boards can therefore be placed, resulting in financial savings.
As the laser beam may be freely and rapidly moved both in the x and y directions, eliminating irregularly shaped boards is easy. This contrasts with a few of the other described methods, which is often limited to straight line cuts. This becomes advantageous with flex boards, which can be very irregularly shaped and in some instances require extremely precise cuts, for instance when conductors are close together or when ZIF connectors must be cut out . These connectors require precise cuts on both ends in the connector fingers, whilst the fingers are perfectly centered in between the two cuts.
A prospective problem to take into consideration will be the precision of the board images on the panel. The authors have not yet found an industry standard indicating an expectation for board image precision. The closest 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 the cutline can be put precisely and closely lmuteg the board, in this case, near the outside of the copper edge ring.
Even when ignoring this potential problem, the minimum space between boards on the panel can be as low as the cutting kerf plus 10 to 30µm, depending on the thickness from the panel as well as the system accuracy of 25µm.
Inside the area protected by the galvo scanner, the beam comes straight down in the center. Even though a large collimating lens is utilized, toward the sides of the area the beam features a slight angle. This means that depending on the height of the components close to the cutting path, some shadowing might occur. Because this is completely predictable, the space some components need to stay removed from the cutting path can be calculated. Alternatively, the scan area may be reduced to side step this issue.
Stress. Because there is no mechanical exposure to the panel during cutting, occasionally each of the depaneling can be carried out after assembly and soldering. What this means is the boards become completely separated from the panel in this last process step, and there is not any necessity 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 susceptible to damage.
Inside our tests stress measurements were performed. During mechanical depaneling an important snap was observed. This too signifies that during earlier process steps, including paste printing and component placement, the panel can maintain its full rigidity with no pallets are essential.
A common production strategy is to pre-route the panel before assembly (mechanical routing, using a ~2 to 3mm routing tool). Rigidity will then be determined by the dimensions and volume of the breakout tabs. The last depaneling step will generate even less debris, and making use of this method laser cutting time is reduced.
After many tests it has become remove the sidewall from the cut path can be very neat and smooth, regardless of the layers in the FR-4 boards or PCB Laser Depaneling. If the requirement for a clean cut is not really very high, like 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 can find no protruding fibers or rough edges, nor exist gaps or delamination that will permit moisture ingress over time . Polyimide, as used in flex circuits, cuts well and permits for extremely clean cuts, as seen in Figure 3 and then in the electron microscope picture.
As noted, it is necessary to keep the material to get cut from the laser as flat as is possible for maximum cutting. In particular instances, as with cutting flex circuits, it may be as easy as placing the flex on the downdraft honeycomb or even an open cell foam plastic sheet. For circuit boards it may be more difficult, specifically for boards with components on both sides. In those instances it still might be desirable to prepare a fixture that may accommodate odd shapes and components.