A lot of solutions are applied for depaneling printed circuit boards. They include:
Punching/die cutting. This technique demands a different die for PCB Depaneling, which is not just a practical solution for small production runs. The action may be either a shearing or crushing method, but either can leave the board edges somewhat deformed. To lower damage care should be come to maintain sharp die edges.
V-scoring. Typically the panel is scored on sides to your depth of about 30% from the board thickness. After assembly the boards can be manually broken out from the panel. This puts bending strain on the boards that may be damaging to a number of the components, in particular those near to the board edge.
Wheel cutting/pizza cutter. A different strategy to manually breaking the internet after V-scoring is by using a “pizza cutter” to reduce the remaining web. This requires careful alignment involving the V-score and the cutter wheels. It also induces stresses within the board which might affect some components.
Sawing. Typically machines that are employed to saw boards from a panel make use of a single rotating saw blade that cuts the panel from either the very best or even the bottom.
Each of these methods is limited to straight line operations, thus simply for rectangular boards, and all of them to some degree crushes and cuts the board edge. Other methods are definitely more expansive and can include the following:
Water jet. Some say this technology can be achieved; however, the authors have found no actual users of it. Cutting is performed using a high-speed stream of slurry, that is water with an abrasive. We expect it will require careful cleaning after the fact to get rid of the abrasive part of the slurry.
Routing ( nibbling). Most of the time boards are partially routed prior to assembly. The other attaching points are drilled having a small drill size, making it simpler to break the boards out of the panel after assembly, leaving the so-called mouse bites. A disadvantage can be quite a significant lack of panel area for 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 means a lot of panel space will likely be needed for the routed traces.
Laser routing. Laser routing offers a space advantage, because the kerf width is just a few micrometers. As an example, the little boards in FIGURE 2 were initially organized in anticipation that the panel would be routed. In this manner the panel yielded 124 boards. After designing the layout for laser Laser PCB Cutting Machine, the amount of boards per panel increased to 368. So for every 368 boards needed, just one single panel has to be produced instead of three.
Routing can also reduce panel stiffness to the point which a pallet is usually necessary for support during the earlier steps in the assembly process. But unlike the prior methods, routing is not confined to cutting straight line paths only.
Most of these methods exert some degree of mechanical stress on the board edges, which can cause delamination or cause space to develop across the glass fibers. This may lead to moisture ingress, which can reduce 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 have 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 ought to be broken in order to take away the board from your panel. It really is therefore imperative to accept the production methods under consideration during board layout as well as for panelization in order that certain parts and traces usually are not positioned in areas regarded as subject to stress when depaneling.
Room is additionally needed to permit the precision (or lack thereof) with which the tool path can be placed and to take into account any non-precision within the board pattern.
Laser cutting. Probably the most recently added tool to delaminate flex and rigid boards is actually a laser. Inside the SMT industry several types of lasers are now being employed. CO2 lasers (~10µm wavelength) provides 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. Both these laser types produce infrared light and may be called “hot” lasers since they burn or melt the fabric being cut. (Being an aside, these are the laser types, especially the Nd:Yag lasers, typically used to produce stainless-steel stencils for solder paste printing.)
UV lasers (typical wavelength ~355nm), on the contrary, are employed 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 relies on the compromise between performance and cost. To ensure ablation to occur, the laser light needs to be absorbed through the materials to be cut. Inside the circuit board industry these are generally mainly FR-4, glass fibers and copper. When thinking about the absorption rates for these particular 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, as it is focused from the relatively wide beam with 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 known as the throat. The perfect ablation takes place when the energy density placed on the content is maximized, which takes place when the throat of the beam is just inside the material being cut. By repeatedly groing through the identical cutting track, thin layers from the material will likely be vboqdt till the beam has cut right through.
In thicker material it may be essential to adjust the main objective in the beam, because the ablation occurs deeper to the kerf being cut to the material. The ablation process causes some heating from the material but could be optimized to leave 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 have more power and could also be used to depanel circuit boards as much as 1.6mm (63 mils) in thickness.
Temperature. The temperature increase 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 for the same location) is dependent upon the path length, beam speed and whether a pause is added between passes.
A knowledgeable and experienced system operator can select the optimum mixture of settings to ensure a clean cut without any burn marks. There is not any straightforward formula to figure out machine settings; they may be relying on material type, thickness and condition. Depending on the board and its application, the operator can choose fast depaneling by permitting some discoloring or perhaps some carbonization, versus a somewhat slower but completely “clean” cut.