PCB Tech - How to choose the number of PCB connected boards?

How to choose the number of PCB connected boards?

Generally speaking, after the design engineer has finalized the appearance and shape of the printed circuit board(Printed Circuit Board), they should immediately proceed with the plywood/joint/panelization work of the circuit board. The purpose of connecting the board is nothing more than: to increase the output of the production line. Reduce the loss of plates:

The most common connecting board is to combine two or more pieces of the same circuit board into a large circuit board, such as 2 in 1 (two in one), 3 in 1 (three in one), 4 in 1 (four in one), etc. ; It is also used to combine different shapes of circuit boards into a large board, but it is rare, because it is difficult for the production tube to match the exact number of different boards when arranging the production; there are also examples of making the same board into a [yin-yang board], [ Yin Yang board] mostly means top and bottom side configurations. This is usually used on circuit boards with fewer parts, such as mobile phone boards, because it can make full use of the SMT long-term boarding function to increase efficiency, but it has disadvantages It is limited in use and may cause uneven heating. For example, some circuit boards will concentrate heavier parts on one side, and then this side will be used as the second part to avoid the heavier parts from falling. Of course This kind of board cannot use the "Yin-Yang board" design; some boards may have more heat-absorbing parts (such as a large area ATM card reader slot), and it is not suitable for the [Yin-Yang board] design. Of course, there is also a flexible [yin-yang board] playing method that can overcome this problem, but I won't discuss it here for now.

Basically, when designing several connecting boards, the following factors should be considered. It should be noted that in the end, they should be converted into money as the final measurement standard. Considering the best utilization rate of circuit boards, ordinary circuit board manufacturers will have their basic standard board sizes in order to quickly mass produce and reduce costs, such as 16.16"x16.16", 18.32"x18.32", 20.32"x20. 32",... etc. What we have to do is to use up all of these plates as much as possible, that is to say, we must choose a suitable standard plate size to stuff our plates in to achieve the highest utilization rate of the plates. Because the price of the circuit board will be priced according to the size of the board, the more circuit boards can be packed in a board, the cheaper the price of the circuit board. Of course, the price of the circuit board has to consider how many layers of the board, how many holes to drill, whether there is HID... etc.

Consider SMT's production/placement efficiency

SMT processing lines are usually divided into so-called long-term and short-term. Short-term means that the thread is shorter. Most of them only have a fast machine and a slow machine. A few more slow-speed machines. But no matter the length of the line, there will always be a solder paste printing machine. Generally speaking, taking a plywood with a board length of 150mm as an example, it takes about 35-40 seconds to print the solder paste once. If only 2 in 1 plywood is used for input SMT is short-term, so the time allocated for each machine may be about 10 to 26 seconds. Obviously, the time is all lower than the time of solder paste printing, that is to say, the subsequent pasting machines are waiting for the solder paste printing machine, so This results in idle SMT machines and reduces production capacity. If the 2 in 1 connecting plate is changed to 4 in 1, then the efficiency will be improved immediately (output per hour)