Laser depaneling can be carried out with extremely high precision. This makes it extremely useful in situations where areas of the board outline demand close tolerances. In addition, it becomes appropriate when very small boards are involved. Because the cutting path is extremely narrow and will be located very precisely, individual boards can be put closely together on the panel.
The reduced thermal effects suggest that although a laser is involved, minimal temperature increases occur, and therefore 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 location of the Inline PCB Router is software-controlled, which suggests changes 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 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 around 10µm to your high of 20µm, and a few might have was comprised of burned or carbonized material. Their size and number were extremely small, without any conduction was expected between traces and components on the board. If you have desired, an easy cleaning process may be put into remove any remaining particles. This type of process could contain the usage of any kind of wiping having a smooth dry or wet tissue, using compressed air or brushes. One could also have any type of cleaning liquids or cleaning baths without or with ultrasound, but normally would avoid any kind of additional cleaning process, especially an expensive one.
Surface resistance. After cutting a path in these test boards (slot in the midst of the test pattern), the boards were subjected to a climate test (40?C, RH=93%, no condensation) for 170 hr., and 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 this kind of scanner permits the beam to be moved in a extremely high speed along 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 method is employed, which could use fiducials or some other panel or board feature to precisely get the location in which the cut has to be placed. High precision x and y movement systems can be used as large movements together with a galvo scanner for local movements.
In these types of machines, the cutting tool is definitely the laser beam, and it has a diameter of around 20µm. What this means is the kerf cut from the laser is about 20µm wide, as well as the laser system can locate that cut within 25µm with regards to 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 lots of small circuit boards, additional boards can therefore be put, leading to cost benefits.
As the PCB Depaneling Router could 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 may be confined to straight line cuts. This becomes advantageous with flex boards, which are often very irregularly shaped and in some instances require extremely precise cuts, for instance when conductors are close together or when ZIF connectors have to be cut out . These connectors require precise cuts on both ends from the connector fingers, while the fingers are perfectly centered involving the two cuts.
A prospective problem to consider 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 nearest they lsgmjm come is “as essental to drawing.” This challenge can be overcome by adding 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 reduce in Figure 2 that this cutline can be put precisely and closely across the board, in this case, next to the outside of the copper edge ring.
Even though 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 in the panel plus the system accuracy of 25µm.
In the area covered by the galvo scanner, the beam comes straight down at the center. Despite the fact that a big collimating lens is used, toward the edges from the area the beam has a slight angle. Which means that depending on the height of the components nearby the cutting path, some shadowing might occur. As this is completely predictable, the space some components must stay removed from the cutting path can be calculated. Alternatively, the scan area can be reduced to side step this problem.
Stress. As there is no mechanical exposure to the panel during cutting, occasionally each of the depaneling can be performed 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 not subjected to damage.
Within our tests stress measurements were performed. During mechanical depaneling a substantial snap was observed. This also implies that during earlier process steps, like paste printing and component placement, the panel can maintain its full rigidity without any pallets are required.
A common production method is to pre-route the panel before assembly (mechanical routing, employing a ~2 to 3mm routing tool). Rigidity is then dependant on the dimensions and amount of the breakout tabs. The ultimate PCB Depaneler step will generate much less debris, and through this method laser cutting time is reduced.
After many tests it is now remove the sidewall in the cut path can be extremely neat and smooth, whatever the layers within the FR-4 boards or polyimide flex circuits. If the requirement for a clean cut is not high, as with tab cutting of the 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 exist gaps or delamination that will permit moisture ingress with time . Polyimide, as used 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 is essential to keep your material to become cut from the laser as flat as possible for maximum cutting. In some instances, like cutting flex circuits, it could be as simple as placing the flex over a downdraft honeycomb or perhaps an open cell foam plastic sheet. For circuit boards it may be more challenging, especially for boards with components on sides. In those instances it still might be desirable to make a fixture that may accommodate odd shapes and components.