Laser depaneling can be carried out with high precision. This will make it extremely useful in situations where areas of the board outline demand close tolerances. It also becomes appropriate when tiny boards are involved. As 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 suggest that although a laser is involved, minimal temperature increases occur, and thus essentially no carbonization results. Depaneling occurs without physical exposure to the panel and without bending or pressing; therefore there is less possibility of component failures or future reliability issues. Finally, the positioning of the cutting path is software-controlled, meaning alterations 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 with 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 a high of 20µm, and a few may have consisted 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 so desired, a simple cleaning process may be put into remove any remaining particles. Such a process could include the usage of any kind of wiping having 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 an expensive one.
Surface resistance. After cutting a path in these test boards (slot in the midst of the exam pattern), the boards were put through 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 inside the material spanning a small area, 50x50mm (2×2″). Using this kind of scanner permits the beam to be moved in a high speed along the cutting path, in the plethora of approx. 100 to 1000mm/sec. This ensures the beam is incorporated in the same location merely a very short period of time, which minimizes local heating.
A pattern recognition product is employed, which could use fiducials or any other panel or board feature to precisely find the location where the cut needs to be placed. High precision x and y movement systems can be used for large movements together with Pneumatic PCB Depanelizer for local movements.
In these kinds of machines, the cutting tool is the laser beam, and it has a diameter of approximately 20µm. What this means is the kerf cut by 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. To get a panel with a lot of small circuit boards, additional boards can therefore be put, ultimately causing cost benefits.
As the laser beam could be freely and rapidly moved within both the x and y directions, eliminating irregularly shaped boards is straightforward. This contrasts with a number of the other described methods, which can be restricted to straight line cuts. This becomes advantageous with flex boards, which are generally 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 reduce . These connectors require precise cuts on ends from the connector fingers, as the fingers are perfectly centered in between the two cuts.
A possible problem to take into consideration is definitely the precision in the board images on the panel. The authors have not yet found an industry standard indicating an expectation for board image precision. The closest they have come is “as necessary for drawing.” This problem can be overcome by adding greater 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 lmuteg the board, in cases like this, 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 in addition to the system accuracy of 25µm.
Inside the area included in the galvo scanner, the beam comes straight down at the center. Although a large collimating lens is utilized, toward the sides of the area the beam has a slight angle. Which means that depending on the height from the components close to the cutting path, some shadowing might occur. Since this is completely predictable, the space some components must stay removed from the cutting path could be calculated. Alternatively, the scan area can be reduced to side step this challenge.
Stress. Because there is no mechanical contact with the panel during cutting, in some instances all the depaneling can be performed after assembly and soldering. This implies the boards become completely separated from the panel in this particular 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 certainly not subjected to damage.
Within our tests stress measurements were performed. During mechanical depaneling an important snap was observed. This means that during earlier process steps, like paste printing and component placement, the panel can maintain its full rigidity and no pallets are needed.
A standard production technique is to pre-route the panel before assembly (mechanical routing, employing a ~2 to 3mm routing tool). Rigidity will be dependant on the dimensions and volume of the breakout tabs. The last depaneling step will generate much less debris, and through this method laser cutting time is reduced.
After many tests it has become remove the sidewall in the cut path can be quite neat and smooth, no matter the layers inside the FR-4 boards or PCB Laser Depaneling. If the requirement for a clean cut is not high, as with tab cutting of any pre-routed board, the cutting speed could be increased, resulting in some discoloration .
When cutting through epoxy and glass fibers, there are no protruding fibers or rough edges, nor exist gaps or delamination that would permit moisture ingress with time . Polyimide, as found in flex circuits, cuts well and permits for extremely clean cuts, as seen in Figure 3 and then in the electron microscope picture.
As noted, it is actually essential to keep your material to become cut from the laser as flat as you can for optimum cutting. In particular instances, as with cutting flex circuits, it could be as basic 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 could be desirable to prepare a fixture that will accommodate odd shapes and components.