Laser depaneling can be performed with extremely high precision. This will make it extremely valuable in situations where areas of the board outline demand close tolerances. It also becomes appropriate when very small boards are involved. Because the cutting path is quite narrow and can be located very precisely, PCB Depanelizer can be put closely together on the panel.
The reduced thermal effects mean that although a laser is involved, minimal temperature increases occur, and therefore essentially no carbonization results. Depaneling occurs without physical contact with the panel and without bending or pressing; therefore there is less probability of component failures or future reliability issues. Finally, the location of the cutting path is software-controlled, meaning modifications in boards may be handled quickly.
To check the impact for any 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 was made up of powdery epoxy and glass particles. Their size ranged from typically 10µm to some high of 20µm, and 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 include the use of any type of wiping with a smooth dry or wet tissue, using compressed air or brushes. You can also use any kind of cleaning liquids or cleaning baths with or without ultrasound, but normally would avoid any kind of additional cleaning process, especially a costly one.
Surface resistance. After cutting a path within these test boards (slot in the middle of the exam pattern), the boards were subjected to a climate test (40?C, RH=93%, no condensation) for 170 hr., as well as 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 over a small area, 50x50mm (2×2″). Using this type of scanner permits the beam to become moved at a very high speed across the cutting path, in the range of approx. 100 to 1000mm/sec. This ensures the beam is incorporated in the same location merely a very short time, which minimizes local heating.
A pattern recognition system is employed, which can use fiducials or any other panel or board feature to precisely discover the location in which the cut needs to be placed. High precision x and y movement systems are 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 around 20µm. What this means is the kerf cut from the laser is all about 20µm wide, as well as the laser system can locate that cut within 25µm with respect to either panel or board fiducials or 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, ultimately causing cost benefits.
Because the laser beam may be freely and rapidly moved both in the x and y directions, removing irregularly shaped boards is straightforward. This contrasts with a few of the other described methods, which is often confined 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 example when conductors are close together or when ZIF connectors need to be eliminate . These connectors require precise cuts on both ends in the connector fingers, whilst the fingers are perfectly centered involving the two cuts.
A prospective problem to take into consideration is the precision of the board images on the panel. The authors have not found a business standard indicating an expectation for board image precision. The closest they have come is “as essental to drawing.” This issue may be overcome by adding more than three panel fiducials and dividing the cutting operation into smaller sections making use of their own area fiducials. Shows in a sample board eliminate in Figure 2 that the cutline can be placed precisely and closely lmuteg the board, in this case, near the away from the copper edge ring.
Even though ignoring this potential problem, the minimum space between boards on the panel can be as little as the cutting kerf plus 10 to 30µm, depending on the thickness in the panel as well as the system accuracy of 25µm.
In the area protected by the galvo scanner, the beam comes straight down in the center. Despite the fact that a big collimating lens is utilized, toward the edges of the area the beam features a slight angle. Which means that depending on the height from the components near the cutting path, some shadowing might occur. Since this is completely predictable, the space some components must stay taken off the cutting path could be calculated. Alternatively, the scan area may be reduced to side step this challenge.
Stress. As there is no mechanical connection with the panel during cutting, occasionally all the depaneling can be executed after assembly and soldering. This means the boards become completely separated from your panel within this last process step, and there is absolutely no 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 subject to damage.
Inside our tests stress measurements were performed. During mechanical depaneling a significant snap was observed. This too means that during earlier process steps, like paste printing and component placement, the panel can maintain its full rigidity without any pallets are needed.
A common production technique is to pre-route the panel before assembly (mechanical routing, employing a ~2 to 3mm routing tool). Rigidity is then based on the dimensions and amount of the breakout tabs. The ultimate depaneling step will generate even less debris, and by using this method laser cutting time is reduced.
After many tests it has become remove the sidewall in the cut path can be extremely clean and smooth, regardless of the layers in the FR-4 boards or Laser PCB Depaneling. If the requirement for a clean cut is not really very high, as with tab cutting of any pre-routed board, the cutting speed could be increased, leading to 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 as time passes . Polyimide, as found in flex circuits, cuts well and permits for extremely clean cuts, as seen in Figure 3 as well as in the electron microscope picture.
As noted, it is essential to keep the material to be cut through the laser as flat as is possible for maximum cutting. In particular instances, like cutting flex circuits, it could be as easy as placing the flex on the downdraft honeycomb or perhaps an open cell foam plastic sheet. For circuit boards it may be harder, specifically for boards with components for both sides. In those instances it might be desirable to make a fixture that will accommodate odd shapes and components.