Array panelization is a manufacturing technique that reduces cost and simplifies the PCB assembly procedure. This technique involves the production of multiple copies of a board (with the same or different designs) by placing them in an array on a standard panel.
Many circuits are very small compared to the panel on which they are printed. To avoid wastage, these small circuits are printed multiple times on the same panel. This is called an array of circuits. Accordingly, a circuit board array is a combination of smaller-sized individual boards connected together to form a larger array of circuits.
All the modern assembly machinery comes with sliding rails that can accommodate these PCB panels. Moving smaller individual boards along these rails one by one would increase the time required for component placement. Hence board arrays on large panels are used.
The panel array is designed with a specific CAD software. The Gerbers of the circuit are imported into the software and replicated multiple times. The placement of these Gerbers is optimized to get the maximum number of PCBs.
Boards should be rotated and flipped in order to accommodate the maximum possible number in the array. After placing the boards, a Gerber file is generated for the whole panel.
The individual PCBs arranged in a panel should ideally be oriented (rotated) in the same direction. If they are rotated 180 degrees off of each other i.e., if one column of boards is flipped 180 degrees with respect to its neighboring column, then the automated machines performing component placement will undergo extra labor. The same is the case with AOI inspection machines.
But sometimes to accommodate more circuit boards in a single panel, they might have to be rotated (inclined). In such cases, it is financially beneficial.
Two common techniques of separation are V-scoring and tab routing.
In this method, the individual circuit boards are separated from each other using V-shaped grooves. An angled blade removes one-third of the board material at the top and bottom.
The main limitation of this method is that it cannot be used when there are components hanging over the edges. V-scoring can also weaken the board array which is not ideal when they have to be wave-soldered.
When the V-scoring technique cannot be used, perforated tabs are employed in between the individual boards. The holes provided in these tabs are called mouse bites. The traces and the surface-mount components are placed at least 3 mm away from these holes. This is to avoid the damage caused to them during board separation after assembly.
A five-hole perforation or a three-hole perforation pattern is used as the standard for these tabs. This is chosen based on the available clearance. In panels where the clearance is limited, three-hole tabs are employed. These tabs should not be placed under overhanging parts.
Depanelization is the process of splitting the individual boards from the array after assembly. Following are the methods of depanelization:
- Breaking by hands: This option is only suitable for arrays that are easily breakable.
- Pizza cutter machine: This machine is used only in the case of V-scored/routed arrays. They are hard to separate using hands. This method is cost-effective and requires low maintenance.
- Punching: In this process, a two-part fixture is used. This fixture punches out the individual boards from the array. This technique can be used for high volumes but the maintenance of this fixture is high.
- Saw: A saw can be used for cutting both V-grooved and non-V-grooved arrays. This can perform cutting at a good speed.
- Laser: Lasers can also be used for carving out the individual boards from the arrays.
Array panelization saves time and labor during high-volume fabrication. Therefore, it is important to take the necessary steps during the paneling and depaneling of arrays.