Laser depaneling can be executed with high precision. This makes it extremely useful in situations where parts of the board outline demand close tolerances. It also becomes appropriate when tiny boards are participating. Since the cutting path is extremely narrow and can be located very precisely, PCB Depanelizer can be placed closely together on the panel.
The reduced thermal effects suggest that although a laser is involved, minimal temperature increases occur, and thus essentially no carbonization results. Depaneling occurs without physical exposure to the panel and without bending or pressing; therefore there exists less probability of component failures or future reliability issues. Finally, the position of the cutting path is software-controlled, which means modifications in boards can be handled quickly.
To evaluate the impact of the 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 comprised of powdery epoxy and glass particles. Their size ranged from around 10µm to your high of 20µm, plus some may have was made up of burned or carbonized material. Their size and number were extremely small, and no conduction was expected between traces and components on the board. If you have desired, a simple cleaning process could be added to remove any remaining particles. This type of process could consist of using any kind of wiping using a smooth dry or wet tissue, using compressed air or brushes. You can also have any type of cleaning liquids or cleaning baths without or with ultrasound, but normally would avoid any type of additional cleaning process, especially an expensive one.
Surface resistance. After cutting a path in these test boards (slot in the center of the exam pattern), the boards were subjected 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 inside the material spanning a small area, 50x50mm (2×2″). Using such a scanner permits the beam to be moved with a high speed across the cutting path, in all the different approx. 100 to 1000mm/sec. This ensures the beam is within the same location just a very short period of time, which minimizes local heating.
A pattern recognition product is employed, which may use fiducials or other panel or board feature to precisely find the location where cut needs to be placed. High precision x and y movement systems can be used for large movements in conjunction with Motorized PCB Depanelizer for local movements.
In these kinds of machines, the cutting tool is the laser beam, and features a diameter of approximately 20µm. This implies the kerf cut by the laser is 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 a panel with a lot of small circuit boards, additional boards can therefore be put, leading to cost savings.
Because the laser beam may be freely and rapidly moved within both the x and y directions, eliminating irregularly shaped boards is straightforward. 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 are often very irregularly shaped and occasionally 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 ends from the connector fingers, whilst the fingers are perfectly centered between the two cuts.
A possible problem to take into consideration is the precision from the board images on the panel. The authors have not yet found a business standard indicating an expectation for board image precision. The closest they have come is “as essental to drawing.” This issue can be overcome with the help of a lot more than three panel fiducials and dividing the cutting operation into smaller sections with their own area fiducials. Shows in a sample board cut out in Figure 2 that the cutline can be placed precisely and closely lmuteg the board, in this instance, near the outside the copper edge ring.
Even if ignoring this potential problem, the minimum space between boards on the panel may be as little as the cutting kerf plus 10 to 30µm, depending on the thickness of the panel as well as the system accuracy of 25µm.
Inside the area protected by the galvo scanner, the beam comes straight down at the center. Although a large collimating lens is utilized, toward the edges of the area the beam features a slight angle. Which means that depending on the height of the components near the cutting path, some shadowing might occur. Since this is completely predictable, the space some components need to stay taken off the cutting path may be calculated. Alternatively, the scan area may be reduced to side step this challenge.
Stress. As there is no mechanical exposure to the panel during cutting, in some instances all of the depaneling can be executed after assembly and soldering. This implies the boards become completely separated from your 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 close to the edge of the board usually are not subjected to damage.
Within our tests stress measurements were performed. During mechanical depaneling a significant snap was observed. This also means that during earlier process steps, such as paste printing and component placement, the panel can maintain its full rigidity with no pallets are needed.
A standard production technique is to pre-route the panel before assembly (mechanical routing, employing a ~2 to 3mm routing tool). Rigidity will be determined by the size and style and quantity of the breakout tabs. The final depaneling step will generate much less debris, and by using this method laser cutting time is reduced.
After many tests it has become remove the sidewall of the cut path can be quite clean and smooth, regardless of the layers inside the FR-4 boards or Laser PCB Depaneling. If the need for a clean cut is not really high, like tab cutting of any pre-routed board, the cutting speed can be increased, leading to some discoloration .
When cutting through epoxy and glass fibers, there are no protruding fibers or rough edges, nor exist gaps or delamination that could permit moisture ingress over time . Polyimide, as found 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 really is required to maintain the material to become cut by the laser as flat as is possible for maximum cutting. In certain instances, as in cutting flex circuits, it could be as easy as placing the flex over a downdraft honeycomb or an open cell foam plastic sheet. For circuit boards it might be harder, especially for boards with components for both sides. In those instances it still could be desirable to make a fixture that may accommodate odd shapes and components.