Quite a few approaches are practiced for depaneling printed circuit boards. They consist of:
Punching/die cutting. This method needs a different die for PCB Depaneling, which can be not just 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 has to be come to maintain sharp die edges.
V-scoring. Often the panel is scored on sides to some depth of about 30% of the board thickness. After assembly the boards may be manually broken from the panel. This puts bending strain on the boards which can be damaging to a number of the components, particularly those near the board edge.
Wheel cutting/pizza cutter. Another method to manually breaking the internet after V-scoring is to apply a “pizza cutter” to slice the remaining web. This involves careful alignment between the V-score and also the cutter wheels. It also induces stresses in the board which might affect some components.
Sawing. Typically machines that are used to saw boards away from a panel use a single rotating saw blade that cuts the panel from either the best or the bottom.
All these methods has limitations to straight line operations, thus simply for rectangular boards, and each one for some degree crushes and/or cuts the board edge. Other methods are more expansive and may include the following:
Water jet. Some say this technology can be achieved; however, the authors have discovered no actual users of it. Cutting is conducted having a high-speed stream of slurry, which can be water with an abrasive. We expect it should take careful cleaning right after the fact to remove the abrasive portion of the slurry.
Routing ( nibbling). Most of the time boards are partially routed prior to assembly. The other attaching points are drilled with 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 could be a significant loss of panel area to the routing space, because the kerf width typically takes up to 1.5 to 3mm (1/16 to 1/8″) plus some additional space for inaccuracies. What this means is lots of panel space is going to be necessary for the routed traces.
Laser routing. Laser routing supplies a space advantage, because the kerf width is simply a few micrometers. For instance, the tiny boards in FIGURE 2 were initially laid out in anticipation the panel would be routed. In this fashion the panel yielded 124 boards. After designing the design for laser Laser PCB Cutting Machine, the number of boards per panel increased to 368. So for each and every 368 boards needed, just one single panel has to be produced as opposed to three.
Routing could also reduce panel stiffness to the point that a pallet may be needed for support throughout the earlier steps within the assembly process. But unlike the earlier methods, routing is not really restricted to cutting straight line paths only.
Many of these methods exert some extent of mechanical stress on the board edges, which can cause delamination or cause space to produce across the glass fibers. This can lead to moisture ingress, which 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 really is accomplished by breaking these final bridges, causing some mechanical and bending stress on the boards. Again, such bending stress may be damaging to components placed near to areas that need to be broken in order to remove the board through the panel. It really is therefore imperative to take the production methods under consideration during board layout and then for panelization so that certain parts and traces are not placed in areas considered to be subjected to stress when depaneling.
Room is additionally required to permit the precision (or lack thereof) with which the tool path may be placed and to look at any non-precision in the board pattern.
Laser cutting. By far the most recently added tool to delaminate flex and rigid boards is actually a laser. Within the SMT industry several types of lasers are now being employed. CO2 lasers (~10µm wavelength) can provide very 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 can be called “hot” lasers as they burn or melt the material being cut. (As being an aside, these are the basic laser types, particularly the Nd:Yag lasers, typically employed to produce stainless stencils for solder paste printing.)
UV lasers (typical wavelength ~355nm), on the other hand, are utilized to ablate the fabric. A localized short pulse of high energy enters the very 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 is based on the compromise between performance and cost. To ensure that ablation to occur, the laser light needs to be absorbed by the materials to be cut. Within the circuit board industry they are mainly FR-4, glass fibers and copper. When thinking about the absorption rates for these particular materials, the shorter wavelength lasers are the most suitable ones for your ablation process. However, the laser cost increases very rapidly for models with wavelengths shorter than 355nm.
The laser beam has a tapered shape, since it is focused coming from a 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 known as the throat. The perfect ablation occurs when the energy density applied to the material is maximized, which takes place when the throat from the beam is merely inside the material being cut. By repeatedly going over exactly the same cutting track, thin layers from the material will be vboqdt until the beam has cut right through.
In thicker material it could be necessary to adjust the main objective of the beam, since the ablation occurs deeper in to the kerf being cut into the material. The ablation process causes some heating from the material but can be optimized to leave no burned or carbonized residue. Because cutting is performed gradually, heating is minimized.
The earliest versions of UV laser systems had enough power to Motorized 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 surge in the content being cut depends on the beam power, beam speed, focus, laser pulse rate and repetition rate. The repetition rate (how fast the beam returns to the same location) depends on the way length, beam speed and whether a pause is added between passes.
An educated and experienced system operator should be able to choose the optimum blend of settings to make sure a clean cut free of burn marks. There is absolutely no straightforward formula to figure out machine settings; they are influenced by material type, thickness and condition. Depending on the board along with its application, the operator can pick fast depaneling by permitting some discoloring or perhaps some carbonization, versus a somewhat slower but completely “clean” cut.