Why do we need to do panelization in PCB production

Why do we need to do panelization in PCB production?

1. Why do we need to do panelization in PCB production? Then after the SMT is finished, you have to cut it into veneers again?

2. What is the use of the break-away/coupon of the PCB?

3. Doesn't it mean that the less the board is used, the cheaper it is? What's the matter with the utilization rate of the board?

Why do PCB production need panelization?

In general circuit board production, the so-called "Panelization" operation is performed, the purpose of which is to increase the production efficiency of the SMT production line.

PCB usually has so-called "several in one" boards, such as two-in-one (2 in 1), four-in-one (4 in 1)...etc.

If you have the opportunity to walk on the SMT production line, you will find that the biggest bottleneck of the SMT production line is actually the "Solder paste printing" process, because no matter how big the PCB is, the cost of printing it The time is almost always around 25 seconds, that is to say, if the time spent by the high-speed patcher and general-purpose patcher with a higher unit price behind it is less than that of the solder paste printer, it will be empty and wait. From an economic point of view, this is a waste.

In fact, the speed of the placement machine is very fast, as fast as one second, several parts can be printed, and some placement machines even have several nozzles that can be printed at the same time. Judging from the number of parts on the current mobile phone PCBA, if there is only a single For a board, it should take less than 10 seconds to complete all the placement operations, so the PCB is assembled to increase the number of parts for placement, which can increase the utilization rate of the placement machine and improve efficiency. Of course, it is best to achieve "Line Balance" so that each device can fully function.

There is another advantage of PCB jigsaw. It can save time when picking and placing PCBA, because multiple boards can be picked and placed at the same time at one time. If the subsequent board level test can be done with the board test, it can also greatly save the board in the fixture. Man-hours wasted in pick and place.

Finally, some boards have irregular shapes when they are designed, such as this [L]-shaped board. If it is made into "Plan 1", there will be a piece of scrap in the upper left corner. If it can be designed to be up and down The upside-down puzzle can greatly reduce the waste, which is the concept of improving the utilization rate of PCB boards.

Disadvantages and limitations of PCB panelization

▪ Although there are many advantages of PCB paneling, when all the PCBA assembly operations are completed, it still has to be cut (de-panel) into a single board. With one more process, it will increase the man-hours and increase the transportation of collision parts. risks of.

▪ If there are too small parts such as thin feet and 0201 on some boards, the number of panels should not be too large, because there is a tolerance between veneer and veneer. If there are too many panels, the tolerance may be too large. To meet the precision requirements of solder paste printing, the final solder paste printing is biased, and there is a problem with the solder.

▪ Some PCBs that are too thin are not recommended to have too many panels, because the thinner the PCB, the greater the deformation. Too many panels will become wider, and patching and reflow ovens are all tests. Of course, this aspect can be overcome by using a furnace vehicle or a full-time vehicle, but the cost of the vehicle and the increased labor cost must be considered.

What is the purpose of PCB break-away?

The break-away of the PCB is also called coupon by some foreigners. Because it is similar to the discount roll of the supermarket, it can be directly broken. However, based on quality considerations, it is really not recommended to break the excess board with your hands. Machine equipment (Scoring, Router) should be used to remove the edge of the board to reduce the impact of the stress generated by the edge of the folded board on the board and parts.

The main purpose of PCB edge design is to assist CBA assembly and production. The current SMT production line is actually very highly automated, and the transportation of boards is based on belts and chains. You should have already thought that the main purpose of the edge of the board is to transport the boards for these belts and chains.

Of course, if you want, you can also leave a certain space around the board without placing any electronic parts. Generally, it is required to keep at least 5.0mm or more, because the iron chain of the reflow oven needs to use a relatively deep board edge position. This gives you the opportunity to not need to design the edge, otherwise the belt and chain may damage the electronic parts around it.

In addition, the edge of the PCB has other uses:

▪ "Tooling Hole" can be placed for positioning the board during ICT or FVT testing after SMT process, so as to avoid the needle bed and the test point shifting.

▪ Used as SMT production line sensor to detect the position of circuit board. Generally, each machine on the SMT production line will have a sensor to detect whether a subsequent board arrives to ensure that only one panel is working in the machine, otherwise the patching operation of the previous panel has not been completed. Another piece of the puzzle slams in, and the machine gets messed up, not knowing which piece to hit. And some veneer shapes may just be empty in the place where the sensor of the SMT production line is detected, usually at the front edge of the upper left corner of the board. At this time, the edge of the board can be used to achieve solid detection for the sensor. the goal of.

▪ Some veneer boards can be placed on the edge of the board when too many fiducial marks cannot be set due to space constraints. However, it is recommended that there should also be fiducial marks on the part tray near the thin feet in the board. , which can increase the accuracy of the patch.