Laser depaneling can be carried out with extremely high precision. This makes it extremely useful in situations where parts of the board outline demand close tolerances. In addition, it becomes appropriate when tiny boards are participating. As the cutting path is quite narrow and can be located very precisely, PCB Depanelizer may be placed closely together on the panel.
The low thermal effects mean that even though 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 exists less probability of component failures or future reliability issues. Finally, the position of the cutting path is software-controlled, which suggests modifications in boards may 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 consisted of powdery epoxy and glass particles. Their size ranged from typically 10µm to some high of 20µm, plus 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, a simple cleaning process might be added to remove any remaining particles. Such a process could include using just about any wiping with a smooth dry or wet tissue, using compressed air or brushes. You could also use any kind of cleaning liquids or cleaning baths without or with ultrasound, but normally would avoid just about any additional cleaning process, especially a costly one.
Surface resistance. After cutting a path in these test boards (slot in the midst 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 works with a galvanometer scanner (or galvo scanner) to trace the cutting path within the material more than a small area, 50x50mm (2×2″). Using such a scanner permits the beam to get moved with a high speed across 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 product is employed, which could use fiducials or other panel or board feature to precisely get the location where cut must be placed. High precision x and y movement systems can be used as large movements together with Motorized PCB Depanelizer for local movements.
In these types of machines, the cutting tool will be the laser beam, and it has a diameter of approximately 20µm. This implies 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 put very close together in a panel. For a panel with a lot of small circuit boards, additional boards can therefore be put, resulting in financial savings.
Because the laser beam can be freely and rapidly moved in both the x and y directions, cutting out irregularly shaped boards is easy. This contrasts with a number of the other described methods, which is often confined to straight line cuts. This becomes advantageous with flex boards, which are generally very irregularly shaped and occasionally require extremely precise cuts, as an example when conductors are close together or when ZIF connectors need to be eliminate . These connectors require precise cuts for both ends of the connector fingers, whilst the fingers are perfectly centered involving the two cuts.
A potential problem to take into consideration is the precision in the board images on the panel. The authors have not even found a niche standard indicating an expectation for board image precision. The closest they have come is “as necessary for drawing.” This challenge may be overcome by adding 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 put precisely and closely lmuteg the board, in cases like this, next to the outside the copper edge ring.
Even though ignoring this potential problem, the minimum space between boards on the panel can be as low as the cutting kerf plus 10 to 30µm, depending on the thickness from the panel in addition to the system accuracy of 25µm.
Within the area included in the galvo scanner, the beam comes straight down at the center. Despite the fact that a sizable collimating lens can be used, toward the sides from the area the beam has a slight angle. Which means that depending on the height from the components nearby the cutting path, some shadowing might occur. Since this is completely predictable, the distance some components have to stay taken off the cutting path can be calculated. Alternatively, the scan area may be reduced to side step this challenge.
Stress. While there is no mechanical connection with 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 through the panel in this last process step, and there is not any requirement 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 certainly not subjected to damage.
In our tests stress measurements were performed. During mechanical depaneling a significant snap was observed. This too implies that during earlier process steps, including paste printing and component placement, the panel can maintain its full rigidity and no pallets are required.
A typical production technique 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 volume of the breakout tabs. The final depaneling step will generate even less debris, and through 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, no matter the layers in the FR-4 boards or PCB Laser Depaneling. If the need for a clean cut will not be high, as in tab cutting of the pre-routed board, the cutting speed could be increased, resulting in some discoloration .
When cutting through epoxy and glass fibers, you will find no protruding fibers or rough edges, nor exist gaps or delamination that will permit moisture ingress with time . Polyimide, as utilized in flex circuits, cuts well and permits for extremely clean cuts, as observed in Figure 3 and then in the electron microscope picture.
As noted, it is actually necessary to keep your material to be cut through the laser as flat as 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 even an open cell foam plastic sheet. For circuit boards it might be harder, particularly for boards with components on sides. In those instances it still may be desirable to make a fixture that will accommodate odd shapes and components.