Many techniques are used for depaneling printed circuit boards. They include:
Punching/die cutting. This method requires a different die for PCB Depaneling, which is not really a practical solution for small production runs. The action could be either a shearing or crushing method, but either can leave the board edges somewhat deformed. To lower damage care must be delivered to maintain sharp die edges.
V-scoring. Usually the panel is scored on sides to a depth of about 30% in the board thickness. After assembly the boards could be manually broken from the panel. This puts bending strain on the boards which can be damaging to a few of the components, particularly those near the board edge.
Wheel cutting/pizza cutter. Another approach to manually breaking the net after V-scoring is to use a “pizza cutter” to slice the rest of the web. This calls for careful alignment in between the V-score and the cutter wheels. It also induces stresses in the board which may affect some components.
Sawing. Typically machines that are used to saw boards from a panel use a single rotating saw blade that cuts the panel from either the best or the bottom.
Each of these methods is limited to straight line operations, thus simply for rectangular boards, and each one to a few degree crushes and/or cuts the board edge. Other methods are definitely more expansive and can include these:
Water jet. Some say this technology can be done; however, the authors are finding no actual users of it. Cutting is carried out using a high-speed stream of slurry, which can be water with an abrasive. We expect it will need careful cleaning after the fact to remove the abrasive portion of the slurry.
Routing ( nibbling). Usually boards are partially routed just before assembly. The remaining attaching points are drilled using a small drill size, making it easier to break the boards out of the panel after assembly, leaving the so-called mouse bites. A disadvantage can be quite a significant loss in panel area to 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 implies a lot of panel space will likely be necessary for the routed traces.
Laser routing. Laser routing provides a space advantage, as the kerf width is just a few micrometers. For example, the small boards in FIGURE 2 were initially presented in anticipation that this panel could be routed. In this way the panel yielded 124 boards. After designing the design for laser Laser PCB Cutting Machine, the amount of boards per panel increased to 368. So for each and every 368 boards needed, just one single panel needs to be produced instead of three.
Routing could also reduce panel stiffness to the stage that the pallet may be required for support during the earlier steps inside the assembly process. But unlike the earlier methods, routing will not be confined to cutting straight line paths only.
Many of these methods exert some degree of mechanical stress on the board edges, which can lead to delamination or cause space to develop across the glass fibers. This might lead to moisture ingress, which in turn is effective in reducing the long-term longevity of the circuitry.
Additionally, when finishing placement of components on the board and after soldering, the final connections involving the boards and panel need to be removed. Often this can be accomplished by breaking these final bridges, causing some mechanical and bending stress on the boards. Again, such bending stress could be damaging to components placed near areas that should be broken so that you can take away the board from your panel. It is therefore imperative to take the production methods into account during board layout and for panelization in order that certain parts and traces are not placed in areas regarded as subjected to stress when depaneling.
Room can also be needed to permit the precision (or lack thereof) that the tool path may be placed and to look at any non-precision inside the board pattern.
Laser cutting. By far the most recently added tool to delaminate flex and rigid boards is really a laser. In the SMT industry several types of lasers are 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. Both these laser types produce infrared light and could be called “hot” lasers because they burn or melt the content being cut. (As being an aside, these are the basic laser types, particularly the Nd:Yag lasers, typically used to produce stainless stencils for solder paste printing.)
UV lasers (typical wavelength ~355nm), on the contrary, are utilized to ablate the content. A localized short pulse of high energy enters the best layer from the material being processed and essentially vaporizes and removes this top layer explosively, turning it to dust.
Deciding on a a 355nm laser relies on the compromise between performance and price. To ensure that ablation to occur, the laser light has to be absorbed by the materials to get cut. Inside the circuit board industry these are generally mainly FR-4, glass fibers and copper. When examining the absorption rates for these materials, the shorter wavelength lasers are the most appropriate ones for the ablation process. However, the laser cost increases very rapidly for models with wavelengths shorter than 355nm.
The laser beam includes a tapered shape, because it is focused from the relatively wide beam with an extremely narrow beam and after that continuous in a reverse taper to widen again. This small area where the beam are at its most narrow is called the throat. The perfect ablation occurs when the energy density applied to the fabric is maximized, which occurs when the throat from the beam is just in the material being cut. By repeatedly going over the same cutting track, thin layers of the material will likely be vboqdt up until the beam has cut all the way through.
In thicker material it could be essential to adjust the focus in the beam, because the ablation occurs deeper in to the kerf being cut to the material. The ablation process causes some heating from the material but may be optimized to go out of no burned or carbonized residue. Because cutting is carried out gradually, heating is minimized.
The earliest versions of UV laser systems had enough power to Manual PCB Depaneling. Present machines get more power and can also be used to depanel circuit boards as much as 1.6mm (63 mils) in thickness.
Temperature. The temperature rise in the material being cut depends on the beam power, beam speed, focus, laser pulse rate and repetition rate. The repetition rate (how quickly the beam returns to the same location) is dependent upon the road length, beam speed and whether a pause is added between passes.
An experienced and experienced system operator will be able to pick the optimum combination of settings to make sure a clean cut without any burn marks. There is absolutely no straightforward formula to determine machine settings; they are relying on material type, thickness and condition. Depending on the board and its application, the operator can select fast depaneling by permitting some discoloring or perhaps some carbonization, versus a somewhat slower but completely “clean” cut.