Laser depaneling can be performed with extremely high precision. This will make it extremely beneficial in situations where areas of the board outline demand close tolerances. It also becomes appropriate when really small boards are involved. As the cutting path is extremely narrow and can be located very precisely, individual boards can be put closely together on the panel.
The low thermal effects suggest that even though 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 exists less possibility of component failures or future reliability issues. Finally, the position of the PCB Router is software-controlled, which means changes in boards can 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 having 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 comprised 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, a basic cleaning process could be added to remove any remaining particles. This kind of process could include the use of any type 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 with or without ultrasound, but normally would avoid just about any additional cleaning process, especially a high priced one.
Surface resistance. After cutting a path during 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 works with a galvanometer scanner (or galvo scanner) to trace the cutting path in the material over a small area, 50x50mm (2×2″). Using this type of scanner permits the beam to get moved with a very high speed along the cutting path, in the range of approx. 100 to 1000mm/sec. This ensures the beam is within the same location merely a very limited time, which minimizes local heating.
A pattern recognition method is employed, which may use fiducials or any other panel or board feature to precisely discover the location where the cut needs to be placed. High precision x and y movement systems can be used as large movements in combination with a galvo scanner for local movements.
In these types of machines, the cutting tool will be the laser beam, and contains a diameter of around 20µm. This implies the kerf cut from the laser is about 20µm wide, and the laser system can locate that cut within 25µm regarding either panel or board fiducials or other board feature. The boards can therefore be put very close together in a panel. For any panel with a lot of small circuit boards, additional boards can therefore be placed, ultimately causing financial savings.
As the PCB Depaneling Router can be freely and rapidly moved both in the x and y directions, cutting out irregularly shaped boards is straightforward. This contrasts with some of the other described methods, which is often confined to straight line cuts. This becomes advantageous with flex boards, which are often very irregularly shaped and occasionally require extremely precise cuts, for example when conductors are close together or when ZIF connectors have to be cut out . These connectors require precise cuts on ends from the connector fingers, as the fingers are perfectly centered in between the two cuts.
A prospective problem to take into consideration is definitely the precision of 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 lsgmjm come is “as essental to drawing.” This issue may be overcome with the help of a lot 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 cut out in Figure 2 the cutline may be placed precisely and closely across the board, in this instance, next to the outside of the copper edge ring.
Even when 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 of the panel plus the system accuracy of 25µm.
In the area covered by the galvo scanner, the beam comes straight down in the middle. Even though a sizable collimating lens can be used, toward the sides from the area the beam has a slight angle. This means that depending on the height in the components nearby the cutting path, some shadowing might occur. Because this is completely predictable, the distance some components need to stay removed from the cutting path can be calculated. Alternatively, the scan area could be reduced to side step this challenge.
Stress. Because there is no mechanical exposure to the panel during cutting, occasionally all the depaneling can be executed after assembly and soldering. This implies the boards become completely separated through the panel in this particular 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 are certainly not subjected to damage.
In our tests stress measurements were performed. During mechanical depaneling a significant snap was observed. This too means that during earlier process steps, including paste printing and component placement, the panel can maintain its full rigidity and no pallets are needed.
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 based on the size and volume of the breakout tabs. The last PCB Separator step will generate much less debris, and through this method laser cutting time is reduced.
After many tests it has become remove the sidewall from the cut path can be quite clean and smooth, whatever the layers in the FR-4 boards or polyimide flex circuits. If the requirement for a clean cut will not be extremely high, like tab cutting of the pre-routed board, the cutting speed could be increased, leading to some discoloration .
When cutting through epoxy and glass fibers, you can find no protruding fibers or rough edges, nor exist gaps or delamination that would permit moisture ingress over time . Polyimide, as utilized in flex circuits, cuts well and permits for extremely clean cuts, as observed in Figure 3 as well as in the electron microscope picture.
As noted, it really is essential to keep your material to be cut by the laser as flat as you can for maximum cutting. In some instances, as with cutting flex circuits, it could be as basic as placing the flex on the downdraft honeycomb or an open cell foam plastic sheet. For circuit boards it may be more challenging, specifically for boards with components for both sides. In those instances still it may be desirable to get ready a fixture that can accommodate odd shapes and components.