When you design your PCBs and send them to manufacture, you have to provide to the manufacturer your design in a correct way they can do the work. You will have to put all your designs in a panel so they can build them.
When you request PCBs, the manufacturer will use a panel of the material you will request. There are different sizes of panels, but you will have to take into account that, typically, independently of the units you require, at least you will pay the price of a panel.
When the panel is manufactured, not only your PCBs are fabricated but also some additional marks are put in the panel, like the identification of the work, or fiducial points that will be used for other tasks in the panel. There are different panel sizes, but you need to have in mind your panel needs to be smaller than this maximum size because the external parts of the panel cannot be used, for different reasons. First one is because it will be used by the manufacturer as commented before to put marks, and the second one, in the external parts of the panel there are more possibilities to have problems with the PCBs, like increase the possibility of the PCB breaks or bend, obtaining bad PCBs.
When you request to manufacture PCBs, you can ask to receive them as individual components or you can receive them in a panel.
If you request to receive the PCBs as individual components they will only be valid if you want to solder by hand all the components, because they will not valid for pick and place machines. You will have to select the different number of circuits you will ask, the size of them and finally the number of units of each PCB.
When you select this option, you will have to provide your PCBs panelized. You can request to receive your panel in two different ways, depending on how the cut out of each PCB is done, using V-scoring or tab route. You will also have to select or tell to the manufacturer if you accept X-out allowance in your panel. If you accept it, you can receive some board with fails, since some problem in some of the boards (maximum 10-20% of the boards) can occur. If you do not accept, spare units will be processed to consider the possible options of a failure, but the cost will be increased.
V-scoring is based in milling the line that separates adjacent boards, in both top and bottom of the panel, with the shape of a V, but without breaking the panel, to easily separate manually the boards when the customer receives the panel.
When you design your panel and select this method to separate your PCBs you will need to have in mind you are generating an array. Therefore, all the elements of each column of the array will need to have the same width and all the elements of each row of the array will need to have the same height. This also limits the shape of each board to a square or rectangle shape. The size of your panel should fit inside the possible sizes your manufacturer provides you, taking into account the borders cannot be used. Typically, around 2.5 cm of each side of the panel cannot be used.
Tab route consists in placing tabs to separate one PCB from another. Then, when the milling process is done, all the PCBs will be attached among them inside the panel. The copper of these tabs will be milled to easily break the tabs when the PCBs are separated. It is also recommended to put via holes in the tabs, close to the borders of the PCBs to help to break the tabs. This is very important when dealing with thick substrates or multilayer printed circuit boards. Unlike V-scoring in which the PCBs are placed very close one to another, only the separation to make the cut-out, in the tab-route option a higher distance has to be considered.
Typically, is around three times the size of the tool will be used to make the cut-out route. Then the distance between PCBs required is to have at least 1.6 mm between them. This allows that, once the cut out of both PCBs is done, the quantity of substrate is enough to not break the panel. It is recommended to put at least one tabs in each axis of each board to have each PCB well stabilized.
V-scoring option is indicated when dealing with PCBs with same and easy shapes (square or rectangle) while tab route option is the required when complex shapes are required.
V-scoring will be cheaper with respect tab route since the substrate will be better optimized, the tooling costs will be lower and the time to manufacture the panel will be lower.
To panelize a V-scoring panel is a quick task for the customer, but to panelize a complex panel can take too much time and it is possible the tabs are not placed in the optimum placement from the manufacturer point of view. On the other hand, the designer will have the possibility to place the tabs in the positions that will better fit from the electrical point of view.
On the other hand, tab route will give you a higher degree of freedom when multiple shapes of PCBs are required, especially when prototyping.
With this option, the manufacturer will panelize the panel for you. You will have to select the same options (v-scoring or tab route) than when you do the panel by yourself, but without taking the effort to panelize your printed circuit boards. On the contrary, the price could be higher. Additionally, you will have to select if you want that your panel has edge rails. Edge rails are parallel edges placed in the borders of the panel that will help to the PCB assembly when dealing with automatic pick and place machines.
You will have to provide your PCBs inside the panel, with the requested separation from PCB to PCB but without placing the tabs and cut lines between each board.
The way to receive the PCBs will depend on who is going to solder the PCBs and how is going to be done. If you are going to request the panel is assembled externally using pick and place machines your panel will need to be panelized and with all the fiducial points, edge rails etc so they can do correctly the process.
If you or your team are going to do the work, depending on how you will solder the components you will have to select accordingly the way you will receive the PCBs. If you will solder manually with solder pencil and using wire solder you can select the option of receiving the PCBs individually. So, you could reduce the cost and the time to remove the PCBs from the panel. But, if you are going to do the PCB assembly using solder paste and reflow techniques it will be better for you to select to receive the boards in the corresponding panel. To save time for the integration process it is better you request a stencil to place the solder paste and quickly place and solder the SMD components.
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