A lot of methods are used for depaneling printed circuit boards. They include:
Punching/die cutting. This process needs a different die for PCB Depaneling, that 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 has to be delivered to maintain sharp die edges.
V-scoring. Usually the panel is scored for both sides to some depth of about 30% of the board thickness. After assembly the boards could be manually broken out of the panel. This puts bending strain on the boards that may be damaging to a number of the components, in particular those near the board edge.
Wheel cutting/pizza cutter. Another method to manually breaking the net after V-scoring is to apply a “pizza cutter” to slice the other web. This requires careful alignment between the V-score and also the cutter wheels. It also induces stresses within the board which may affect some components.
Sawing. Typically machines that are employed to saw boards out of a panel make use of a single rotating saw blade that cuts the panel from either the top or even the bottom.
Each one of these methods has limitations to straight line operations, thus just for rectangular boards, and each one for some degree crushes and/or cuts the board edge. Other methods are definitely more expansive and can include the subsequent:
Water jet. Some say this technology can be done; however, the authors have discovered no actual users of this. Cutting is performed having a high-speed stream of slurry, that is water having an abrasive. We expect it will need careful cleaning after the fact to remove the abrasive portion of the slurry.
Routing ( nibbling). More often than not boards are partially routed before assembly. The remaining attaching points are drilled using a small drill size, making it simpler to break the boards from the panel after assembly, leaving the so-called mouse bites. A disadvantage can be a significant loss in panel area for the routing space, since the kerf width often takes approximately 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 required for the routed traces.
Laser routing. Laser routing supplies a space advantage, as 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 fashion the panel yielded 124 boards. After designing the design for laser Laser Depaneling, the amount of boards per panel increased to 368. So for every 368 boards needed, just one single panel must be produced as opposed to three.
Routing can also reduce panel stiffness to the stage that the pallet may be required for support during the earlier steps in the assembly process. But unlike the previous methods, routing is not really limited to cutting straight line paths only.
The majority of these methods exert some extent 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 often can reduce the long-term reliability of the circuitry.
Additionally, when finishing placement of components on the board and after soldering, the final connections between the boards and panel must be removed. Often this is accomplished by breaking these final bridges, causing some mechanical and bending stress on the boards. Again, such bending stress can be damaging to components placed near areas that ought to be broken so that you can remove the board from your panel. It really is therefore imperative to accept the production methods into consideration during board layout as well as for panelization to ensure that certain parts and traces are certainly not put into areas regarded as subjected to stress when depaneling.
Room is also necessary to permit the precision (or lack thereof) in which the tool path may be placed and to look at any non-precision in the board pattern.
Laser cutting. The most recently added tool to delaminate flex and rigid boards is a laser. In the SMT industry several kinds of lasers are now being employed. CO2 lasers (~10µm wavelength) can offer extremely high power levels and cut through thick steel sheets and in addition 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 material being cut. (Being an aside, they are the laser types, especially the Nd:Yag lasers, typically employed to produce stainless steel 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 top layer of the material being processed and essentially vaporizes and removes this top layer explosively, turning it to dust.
The choice of a 355nm laser is based on the compromise between performance and expense. To ensure that ablation to take place, the laser light must be absorbed by the materials to become cut. Inside 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 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 a relatively wide beam with an extremely narrow beam and then continuous in a reverse taper to widen again. This small area where beam are at its most narrow is known as the throat. The ideal ablation happens when the energy density applied to the content is maximized, which happens when the throat from the beam is simply inside the material being cut. By repeatedly exceeding the identical cutting track, thin layers of the material will likely be vboqdt until the beam has cut all the way through.
In thicker material it might be essential to adjust the main focus of the beam, as the ablation occurs deeper into the kerf being cut into the material. The ablation process causes some heating in the material but could be optimized to go out of no burned or carbonized residue. Because cutting is performed gradually, heating is minimized.
The earliest versions of UV laser systems had enough capability to Manual PCB Depaneling. Present machines have more power and may also be used to depanel circuit boards as much as 1.6mm (63 mils) in thickness.
Temperature. The temperature rise in the content 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 determined by the path length, beam speed and whether a pause is added between passes.
An educated and experienced system operator can pick the optimum blend of settings to make sure a clean cut free from burn marks. There is no straightforward formula to determine machine settings; these 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.