A lot of techniques are used for depaneling printed circuit boards. They consist of:
Punching/die cutting. This method requires a different die for PCB Depaneling, which can be 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 taken to maintain sharp die edges.
V-scoring. Typically the panel is scored on sides to your depth of around 30% in the board thickness. After assembly the boards could be manually broken from the panel. This puts bending strain on the boards that may be damaging to a few of the components, particularly those near to the board edge.
Wheel cutting/pizza cutter. Another strategy to manually breaking the net after V-scoring is to use a “pizza cutter” to cut the other web. This involves careful alignment between the V-score and also the cutter wheels. In addition, it induces stresses within the board which might 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 very best or the bottom.
Each of these methods has limitations to straight line operations, thus just for rectangular boards, and each of them 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 achieved; however, the authors have found no actual users of it. Cutting is conducted using a high-speed stream of slurry, which can be water with the abrasive. We expect it will need careful cleaning after the fact to remove the abrasive part of the slurry.
Routing ( nibbling). Usually boards are partially routed prior to assembly. The remaining attaching points are drilled having a small drill size, making it simpler to interrupt the boards from the panel after assembly, leaving the so-called mouse bites. A disadvantage can be a significant lack of panel area to the routing space, because the kerf width typically takes approximately 1.5 to 3mm (1/16 to 1/8″) plus some additional space for inaccuracies. This implies a significant amount of panel space is going to be necessary for the routed traces.
Laser routing. Laser routing provides a space advantage, as the kerf width is just a few micrometers. As an example, the little boards in FIGURE 2 were initially presented in anticipation that this panel would be routed. In this fashion the panel yielded 124 boards. After designing the design for laser Laser PCB Cutting Machine, the quantity of boards per panel increased to 368. So for each and every 368 boards needed, just one single panel has to be produced instead of three.
Routing can also reduce panel stiffness to the level that a pallet is usually necessary for support throughout the earlier steps inside the assembly process. But unlike the previous 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 cause delamination or cause space to develop round the glass fibers. This may 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 ultimate connections between the boards and panel need to be removed. Often this really is 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 close to areas that need to be broken to be able to remove the board through the panel. It is actually therefore imperative to accept the production methods into account during board layout and for panelization in order that certain parts and traces are certainly not positioned in areas regarded as subjected to stress when depaneling.
Room is also necessary to permit the precision (or lack thereof) with which the tool path can be put and to take into consideration any non-precision within the board pattern.
Laser cutting. The most recently added tool to delaminate flex and rigid boards is a laser. Within the SMT industry various kinds lasers are being employed. CO2 lasers (~10µm wavelength) can offer 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 could be called “hot” lasers since they burn or melt the material being cut. (As an aside, these are the laser types, especially the Nd:Yag lasers, typically used to produce stainless stencils for solder paste printing.)
UV lasers (typical wavelength ~355nm), on the other hand, are used to ablate the material. A localized short pulse of high energy enters the best layer of the material being processed and essentially vaporizes and removes this top layer explosively, turning it to dust.
Deciding on a a 355nm laser is situated on the compromise between performance and expense. To ensure ablation to happen, the laser light must be absorbed by the materials to be cut. Within the circuit board industry these are 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 your ablation process. However, the laser cost increases very rapidly for models with wavelengths shorter than 355nm.
The laser beam features a tapered shape, since it is focused coming from a relatively wide beam for an extremely narrow beam then continuous in a reverse taper to widen again. This small area in which the beam reaches its most narrow is called the throat. The perfect ablation happens when the energy density placed on the fabric is maximized, which happens when the throat in the beam is simply in the material being cut. By repeatedly exceeding the same cutting track, thin layers from the material is going to be vboqdt until the beam has cut all the way through.
In thicker material it might be necessary to adjust the focus of the beam, as the ablation occurs deeper to the kerf being cut into 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 done gradually, heating is minimized.
The earliest versions of UV laser systems had enough capacity to Pneumatic PCB Depaneling. Present machines acquire more power and can also be used to depanel circuit boards up to 1.6mm (63 mils) in thickness.
Temperature. The temperature increase in the fabric being cut depends on 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 path length, beam speed and whether a pause is added between passes.
A knowledgeable and experienced system operator can pick the optimum combination of settings to make sure a clean cut without any burn marks. There is not any straightforward formula to determine machine settings; they are influenced by material type, thickness and condition. Depending on the board as well as its application, the operator can choose fast depaneling by permitting some discoloring or even some carbonization, versus a somewhat slower but completely “clean” cut.