Punching/die cutting. This technique requires a different die for every single new circuit board, which happens to be not a practical solution for small production runs. The action may be PCB Depaneling, but either can leave the board edges somewhat deformed. To lower damage care must be taken up maintain sharp die edges.
V-scoring. Typically the panel is scored for both sides to some depth of approximately 30% in the board thickness. After assembly the boards might be manually broken out of the panel. This puts bending force on the boards that could be damaging to a few of the components, in particular those near the board edge.
Wheel cutting/pizza cutter. Another technique to manually breaking the internet after V-scoring is to apply a “pizza cutter” to slice the remaining web. This involves careful alignment between your V-score along with the cutter wheels. Furthermore, it induces stresses within the board which may affect some components.
Sawing. Typically machines that are widely used to saw boards from a panel make use of a single rotating saw blade that cuts the panel from either the very best or maybe the bottom.
Each one of these methods is limited to straight line operations, thus only for rectangular boards, and every one of them to many degree crushes or cuts the board edge. Other methods are definitely more expansive and may include the subsequent:
Water jet. Some say this technology can be achieved; however, the authors have discovered no actual users than it. Cutting is performed by using a high-speed stream of slurry, which can be water with an abrasive. We expect it will require careful cleaning following the fact to remove the abrasive portion of the slurry.
Routing ( nibbling). Quite often boards are partially routed ahead of assembly. The remaining attaching points are drilled using a small drill size, making it easier to get rid of the boards out from the panel after assembly, leaving the so-called mouse bites. A disadvantage can be quite a significant lack of panel area on the routing space, since the kerf width often takes up to 1.5 to 3mm (1/16 to 1/8″) plus some additional space for inaccuracies. This simply means lots of panel space will probably be needed for the routed traces.
Laser routing. Laser routing offers a space advantage, since the kerf width is simply a few micrometers. By way of example, the tiny boards in FIGURE 2 were initially organized in anticipation how the panel can be routed. In this manner the panel yielded 124 boards. After designing the layout for laser depaneling, the volume of boards per panel increased to 368. So for each and every 368 boards needed, only one panel has to be produced instead of three.
Routing also can reduce panel stiffness to the level a pallet may be needed for support through the earlier steps within the assembly process. But unlike the previous methods, routing will not be restricted to cutting straight line paths only.
The majority of these methods exert some degree of mechanical stress in the board edges, which can lead to delamination or cause space to develop round the glass fibers. This may lead to moisture ingress, which helps to reduce the long-term reliability of the circuitry.
Additionally, when finishing placement of components about the board and after soldering, the very last connections involving the boards and panel must be removed. Often this is certainly accomplished by breaking these final bridges, causing some mechanical and bending stress around the boards. Again, such bending stress may be damaging to components placed near to areas that should be broken as a way to eliminate the board from your panel. It is therefore imperative to accept the production methods under consideration during board layout and also for panelization so that certain parts and traces are certainly not placed in areas regarded as susceptible to stress when depaneling.
Room can also be required to permit the precision (or lack thereof) which the tool path can be put and to look at any non-precision inside the board pattern.
Laser cutting. One of the most recently added tool to PCB Routing Machine and rigid boards is actually a laser. From the SMT industry several types of lasers are now being employed. CO2 lasers (~10µm wavelength) provides extremely high power levels and cut through thick steel sheets and also through circuit boards. Neodymium:Yag lasers and fiber lasers (~1µm wavelength) typically provide lower power levels at smaller beam sizes. These two laser types produce infrared light and might be called “hot” lasers while they burn or melt the material being cut. (As an aside, they are the laser types, specially the Nd:Yag lasers, typically utilized to produce steel stencils for solder paste printing.)
UV lasers (typical wavelength ~355nm), alternatively, are used to ablate the information. A localized short pulse of high energy enters the most notable layer of your material being processed and essentially vaporizes and removes this top layer explosively, turning it to dust (FIGURE 3).
Choosing a 355nm laser is founded on the compromise between performance and cost. To ensure that ablation to happen, the laser light has to be absorbed with the materials to be cut. From the circuit board industry these are generally mainly FR-4, glass fibers and copper. When viewing the absorption rates for these particular materials (FIGURE 4), the shorter wavelength lasers are the most suitable ones for the ablation process. However, the laser cost increases very rapidly for models with wavelengths shorter than 355nm.
The laser beam features a tapered shape, because it is focused from the relatively wide beam to a extremely narrow beam and then continuous in a reverse taper to widen again. This small area the location where the beam reaches its most narrow is named the throat. The ideal ablation happens when the energy density put on the fabric is maximized, which happens when the throat from the beam is just inside of the material being cut. By repeatedly groing through the identical cutting track, thin layers of the material will likely be removed until the beam has cut all the way through.
In thicker material it might be essential to adjust the focus of the beam, as the ablation occurs deeper to the kerf being cut in the material. The ablation process causes some heating from the material but can be optimized to go out of no burned or carbonized residue. Because cutting is completed gradually, heating is minimized.
The earliest versions of UV laser systems had enough ability to depanel flex circuit panels. Present machines get more power and could also be used to depanel circuit boards around 1.6mm (63 mils) in thickness.
Temperature. The temperature boost in the content being cut is dependent upon the beam power, beam speed, focus, laser pulse rate and repetition rate. The repetition rate (how rapidly the beam returns towards the same location) is determined by the road length, beam speed and whether a pause is added between passes.
An informed and experienced system operator should be able to select the optimum combination of settings to guarantee a clean cut free from burn marks. There is not any straightforward formula to determine machine settings; these are influenced by material type, thickness and condition. Based on the board and its particular application, the operator can pick fast depaneling by permitting some discoloring or perhaps some carbonization, versus a somewhat slower but completely “clean” cut.
Careful testing indicates that under most conditions the temperature rise within 1.5mm from the cutting path is less than 100°C, way below just what a PCB experiences during soldering (FIGURE 6).
Expelled material. Inside the laser useful for these tests, an airflow goes throughout the panel being cut and removes most of the expelled dust into an exhaust and filtering method (FIGURE 7).
To check the impact associated with a remaining expelled material, a slot was cut inside a four-up pattern on FR-4 material with a thickness of 800µm (31.5 mils) (FIGURE 8). Only few particles remained and was comprised of powdery epoxy and glass particles. Their size ranged from about 10µm to a high of 20µm, and several could have was made up of burned or carbonized material. Their size and number were extremely small, and no conduction was expected between traces and components about the board. In that case desired, an easy cleaning process may be included in remove any remaining particles. Such a process could comprise of the use of any sort of wiping with a smooth dry or wet tissue, using compressed air or brushes. You could also employ any type of cleaning liquids or cleaning baths without or with ultrasound, but normally would avoid any sort of additional cleaning process, especially a pricey one.
Surface resistance. After cutting a path during these test boards (Figure 7, slot in the middle of the test pattern), the boards were subjected to 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 present.
Cutting path location. The laser beam typically relies on 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 become moved with a very high speed along the cutting path, in the range of approx. 100 to 1000mm/sec. This ensures the beam is in the same location simply a very limited time, which minimizes local heating.
A pattern recognition product is employed, which may use fiducials or some other panel or board feature to precisely get the location in which the cut needs to be placed. High precision x and y movement systems can be used for large movements together with a galvo scanner for local movements.
In most of these machines, the cutting tool will be the laser beam, and possesses a diameter of around 20µm. What this means is the kerf cut with the laser is about 20µm wide, and also the laser system can locate that cut within 25µm when it comes to either panel or board fiducials or any other board feature. The boards can therefore be placed very close together in the panel. To get a panel with a lot of small circuit boards, additional boards can therefore be placed, leading to financial savings.
As the laser beam can be freely and rapidly moved within both the x and y directions, eliminating irregularly shaped boards is simple. This contrasts with a few of the other described methods, that may be confined to straight line cuts. This becomes advantageous with flex boards, which can be very irregularly shaped and occasionally require extremely precise cuts, by way of example when conductors are close together or when ZIF connectors should be remove (FIGURE 10). These connectors require precise cuts for both ends of your connector fingers, whilst the fingers are perfectly centered involving the two cuts.
A possible problem to consider is definitely the precision in the board images in the panel. The authors have not found a marketplace standard indicating an expectation for board image precision. The nearest they may have come is “as essental to drawing.” This challenge could be overcome with the help of more than three panel fiducials and dividing the cutting operation into smaller sections making use of their own area fiducials. FIGURE 11 shows in the sample board reduce in Figure 2 that the cutline may be put precisely and closely around the board, in this case, next to the beyond the copper edge ring.
Even though ignoring this potential problem, the minimum space between boards around the panel is often as little as the cutting kerf plus 10 to 30µm, according to the thickness of your panel 13dexopky the system accuracy of 25µm.
Inside the area protected by the galvo scanner, the beam comes straight down in the middle. Though a large collimating lens can be used, toward the edges of your area the beam includes a slight angle. Because of this dependant upon the height of the components near the cutting path, some shadowing might occur. As this is completely predictable, the distance some components must stay removed from the cutting path might be calculated. Alternatively, the scan area might be reduced to side step this concern.
Stress. As there is no mechanical experience of the panel during cutting, in some circumstances every one of the FPC Depaneling Machine can be performed after assembly and soldering (Figure 11). This simply means the boards become completely separated through the panel with this last process step, and there is not any requirement for any bending or pulling about the board. Therefore, no stress is exerted on the board, and components near to the fringe of the board are not at the mercy of damage.
Inside our tests stress measurements were performed. During mechanical depaneling a substantial snap was observed (FIGURES 12 and 13). And also this means that during earlier process steps, for example paste printing and component placement, the panel can maintain its full rigidity with no pallets are needed.