Laser depaneling can be executed with very high precision. This makes it extremely valuable in situations where elements of the board outline demand close tolerances. In addition, it becomes appropriate when very small boards are involved. As the cutting path is quite narrow and may be located very precisely, individual boards can be put closely together on the panel.
The reduced thermal effects imply that although 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 exists less possibility of component failures or future reliability issues. Finally, the location of the Inline PCB Router is software-controlled, meaning modifications in boards could be handled quickly.
To test the impact for any remaining expelled material, a slot was cut in a four-up pattern on FR-4 material using a thickness of 800µm (31.5 mils). Only few particles remained and consisted of powdery epoxy and glass particles. Their size ranged from around 10µm to some high of 20µm, and some might 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 basic cleaning process might be put into remove any remaining particles. This kind of process could contain the usage of any type of wiping with a smooth dry or wet tissue, using compressed air or brushes. You can also employ just about any 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 in these test boards (slot in the midst of the test pattern), the boards were put through 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 inside the material over a small area, 50x50mm (2×2″). Using such a scanner permits the beam to get moved in a 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 limited time, which minimizes local heating.
A pattern recognition product is employed, which can use fiducials or some other panel or board feature to precisely discover the location where cut must be placed. High precision x and y movement systems are used for large movements in combination with a galvo scanner for local movements.
In these sorts of machines, the cutting tool is definitely the laser beam, and it has a diameter of approximately 20µm. This means the kerf cut through the laser is all about 20µm wide, and also the laser system can locate that cut within 25µm with respect to either panel or board fiducials or any other board feature. The boards can therefore be placed very close together in a panel. For any panel with a lot of small circuit boards, additional boards can therefore be placed, ultimately causing cost benefits.
Since the LED PCB Depanelizer may be freely and rapidly moved within both the x and y directions, removing irregularly shaped boards is straightforward. This contrasts with a few of the other described methods, which is often limited 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 must be cut out . These connectors require precise cuts on ends in the connector fingers, whilst the fingers are perfectly centered involving the two cuts.
A prospective problem to consider is definitely the precision in 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 lsgmjm come is “as essental to drawing.” This issue could be overcome with the help of greater than three panel fiducials and dividing the cutting operation into smaller sections with their own area fiducials. Shows in a sample board eliminate in Figure 2 the cutline can be placed precisely and closely round the board, in this instance, 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 of the panel in addition to the system accuracy of 25µm.
Inside the area covered by the galvo scanner, the beam comes straight down in the center. Despite the fact that a sizable collimating lens is used, toward the edges of the area the beam includes a slight angle. This means that depending on the height in the components close to the cutting path, some shadowing might occur. Since this is completely predictable, the space some components must stay taken off the cutting path could be calculated. Alternatively, the scan area could be reduced to side step this issue.
Stress. While there is no mechanical contact with the panel during cutting, occasionally all the depaneling can be executed after assembly and soldering. What this means is the boards become completely separated from your panel within this last process step, and there is absolutely no 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 certainly not subject to damage.
In our tests stress measurements were performed. During mechanical depaneling a significant snap was observed. This also signifies that during earlier process steps, like paste printing and component placement, the panel can maintain its full rigidity with no pallets are required.
A typical production method is to pre-route the panel before assembly (mechanical routing, utilizing a ~2 to 3mm routing tool). Rigidity will then be determined by the dimensions and volume of the breakout tabs. The last PCB Depaneler step will generate even less debris, and making use of this method laser cutting time is reduced.
After many tests it is clear the sidewall of the cut path can be extremely neat and smooth, whatever the layers within the FR-4 boards or polyimide flex circuits. If the necessity for a clean cut is not high, as in tab cutting of a pre-routed board, the cutting speed could be increased, leading to some discoloration .
When cutting through epoxy and glass fibers, there are no protruding fibers or rough edges, nor exist gaps or delamination that will 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 really is necessary to keep your material to get cut from the laser as flat as possible for optimum cutting. In particular instances, as in cutting flex circuits, it could be as simple as placing the flex on 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 might be desirable to make a fixture that will accommodate odd shapes and components.