Laser depaneling can be executed with high precision. This will make it extremely useful in situations where areas of the board outline demand close tolerances. Additionally, it becomes appropriate when really small boards are participating. As the cutting path is quite narrow and can be located very precisely, PCB Depanelizer can be put closely together on the panel.
The low thermal effects imply that although a laser is involved, minimal temperature increases occur, and for that reason 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 position of the cutting path is software-controlled, which means alterations in boards could be handled quickly.
To check the impact of any 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 made up of powdery epoxy and glass particles. Their size ranged from typically 10µm to a high of 20µm, and some 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 put into remove any remaining particles. This kind of process could contain the usage of just about any 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 a high priced one.
Surface resistance. After cutting a path during 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 utilizes a galvanometer scanner (or galvo scanner) to trace the cutting path in the material more than a small area, 50x50mm (2×2″). Using such a scanner permits the beam to be moved with a very high speed along the cutting path, in all the different approx. 100 to 1000mm/sec. This ensures the beam is incorporated in the same location merely a very limited time, which minimizes local heating.
A pattern recognition system is employed, which could use fiducials or some other panel or board feature to precisely find the location in which the cut must be placed. High precision x and y movement systems are used for large movements in combination with Manual PCB Depanelizer for local movements.
In these sorts of machines, the cutting tool will be the laser beam, and contains a diameter of approximately 20µm. What this means is the kerf cut by the laser is 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. To get a panel with a lot of small circuit boards, additional boards can therefore be placed, ultimately causing cost savings.
As the laser beam can be freely and rapidly moved both in the x and y directions, cutting out irregularly shaped boards is easy. This contrasts with some of the other described methods, which can be limited to straight line cuts. This becomes advantageous with flex boards, which can be very irregularly shaped and in some circumstances require extremely precise cuts, for instance when conductors are close together or when ZIF connectors need to be eliminate . These connectors require precise cuts for both ends from the connector fingers, while the fingers are perfectly centered involving 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 even found a business standard indicating an expectation for board image precision. The nearest they may have come is “as essental to drawing.” This issue could be overcome with the addition of a lot more than three panel fiducials and dividing the cutting operation into smaller sections using their own area fiducials. Shows in a sample board reduce in Figure 2 the cutline can be placed precisely and closely lmuteg the board, in cases like this, near the outside of the copper edge ring.
Even when ignoring this potential problem, the minimum space between boards on the panel may be as low as the cutting kerf plus 10 to 30µm, depending on the thickness in the panel as well as the system accuracy of 25µm.
Within the area covered by the galvo scanner, the beam comes straight down in the middle. 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 of the components near the cutting path, some shadowing might occur. As this is completely predictable, the space some components need to stay taken from the cutting path can be calculated. Alternatively, the scan area could be reduced to side step this problem.
Stress. While there is no mechanical contact with the panel during cutting, occasionally each of the depaneling can be performed after assembly and soldering. What this means is the boards become completely separated from the panel in this last process step, and there is no need for any bending or pulling on the board. Therefore, no stress is exerted on the board, and components nearby the fringe of the board are not subject to damage.
Inside our tests stress measurements were performed. During mechanical depaneling a substantial snap was observed. This means that during earlier process steps, including paste printing and component placement, the panel can maintain its full rigidity and no pallets are essential.
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 dependant on the size and style and amount of the breakout tabs. The ultimate depaneling step will generate even less debris, and making use of this method laser cutting time is reduced.
After many tests it is remove the sidewall from the cut path can be quite neat and smooth, regardless of the layers within the FR-4 boards or Laser PCB Depaneling. If the requirement for a clean cut is not extremely high, like tab cutting of a pre-routed board, the cutting speed may be increased, resulting in some discoloration .
When cutting through epoxy and glass fibers, you can find no protruding fibers or rough edges, nor are there gaps or delamination that could permit moisture ingress as time passes . Polyimide, as used in flex circuits, cuts well and permits for extremely clean cuts, as noticed in Figure 3 and then in the electron microscope picture.
As noted, it is actually required to keep your material to become cut through the laser as flat as is possible for maximum cutting. In some instances, like 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 might be more difficult, specifically for boards with components on both sides. In those instances it still may be desirable to make a fixture that may accommodate odd shapes and components.