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. Additionally, it becomes appropriate when really small boards are participating. Since the cutting path is very narrow and can be located very precisely, PCB Depanelizer may be placed closely together on the panel.
The reduced thermal effects mean that even though a laser is involved, minimal temperature increases occur, and thus essentially no carbonization results. Depaneling occurs without physical contact with the panel and without bending or pressing; therefore there is certainly less probability of component failures or future reliability issues. Finally, the positioning of the cutting path is software-controlled, which suggests changes in boards can be handled quickly.
To test 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 was made up of powdery epoxy and glass particles. Their size ranged from an average of 10µm to some high of 20µm, plus some 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. In that case desired, a simple cleaning process could be included in remove any remaining particles. This type of process could contain the usage of any kind of wiping using a smooth dry or wet tissue, using compressed air or brushes. You could also have any kind of cleaning liquids or cleaning baths with or without ultrasound, but normally would avoid any type of additional cleaning process, especially a costly one.
Surface resistance. After cutting a path in 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., as well as the SIR values exceeded 10E11 Ohm, indicating no conductive material is
Cutting path location. The laser beam typically uses a galvanometer scanner (or galvo scanner) to trace the cutting path inside the material more than a small area, 50x50mm (2×2″). Using this type of scanner permits the beam to get moved at a high speed across the cutting path, in the range of approx. 100 to 1000mm/sec. This ensures the beam is in the same location only a very short period of time, which minimizes local heating.
A pattern recognition system is employed, which could use fiducials or some other panel or board feature to precisely get the location in which the cut must be placed. High precision x and y movement systems can be used as large movements in combination with Pneumatic PCB Depanelizer for local movements.
In these types of machines, the cutting tool will be the laser beam, and contains a diameter of around 20µm. This means the kerf cut through the laser is approximately 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. For a panel with a lot of small circuit boards, additional boards can therefore be put, ultimately causing financial savings.
Since the laser beam could be freely and rapidly moved in both 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 can be very irregularly shaped and in some instances require extremely precise cuts, as an example when conductors are close together or when ZIF connectors need to be reduce . 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 in the board images on the panel. The authors have not even found an industry standard indicating an expectation for board image precision. The nearest they may have come is “as required by drawing.” This problem could be overcome by adding greater than three panel fiducials and dividing the cutting operation into smaller sections with their own area fiducials. Shows in a sample board cut out in Figure 2 that the cutline can be placed precisely and closely lmuteg the board, in this case, near the outside 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 of the panel as well as the system accuracy of 25µm.
Within the area included in the galvo scanner, the beam comes straight down in the middle. Although a sizable collimating lens is utilized, toward the sides in 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. As this is completely predictable, the distance some components must stay removed from the cutting path could be calculated. Alternatively, the scan area may be reduced to side step this challenge.
Stress. Because there is no mechanical contact with the panel during cutting, in some instances each of the depaneling can be executed after assembly and soldering. This means the boards become completely separated from the panel within this 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 close to the side of the board usually are not subject to damage.
Within our tests stress measurements were performed. During mechanical depaneling a substantial snap was observed. This also means that during earlier process steps, such as paste printing and component placement, the panel can maintain its full rigidity without any 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 will then be based on the dimensions and volume of the breakout tabs. The final depaneling step will generate even less debris, and making use of this method laser cutting time is reduced.
After many tests it is now remove the sidewall in the cut path can be quite neat and smooth, no matter the layers within the FR-4 boards or PCB Laser Depaneling. If the need for a clean cut is not really high, as with tab cutting of a pre-routed board, the cutting speed could be increased, causing some discoloration .
When cutting through epoxy and glass fibers, you can find no protruding fibers or rough edges, nor are available gaps or delamination that would permit moisture ingress as time passes . Polyimide, as found in flex circuits, cuts well and permits for extremely clean cuts, as seen in Figure 3 and in the electron microscope picture.
As noted, it really is essential to maintain the material to get cut by the laser as flat as possible for maximum cutting. In certain instances, as with cutting flex circuits, it can be as basic as placing the flex on a 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 still it might be desirable to get ready a fixture that may accommodate odd shapes and components.