To put it bluntly, the PCB puzzle is to combine several small PCB units with various connection methods. The more common jigsaw puzzles include AA sequential jigsaw, AB front and back jigsaw, AA rotation jigsaw, AB Yin Yang jigsaw, ABC mixed jigsaw and so on. PCB design engineers usually take into account the functional aspects of the product such as structural size, electrical performance, and component layout when designing the panel. How to improve SMT production efficiency in panel design and minimize the risk of impact on product quality? The case in this article is encountered in the PCBA production process, such as irregular PCB dimensions and impact on production efficiency after panel assembly. , and it also increases production difficulty and manufacturing cost.
Purpose of PCB puzzle:
1. Due to the small size and irregularity of the PCB, the production efficiency of SMT processing is seriously affected
2. Maximize plate utilization and reduce costs
3. Reduce production difficulty and improve product yield.
Rules for board design:
There are many ways of panel design, and sometimes it is difficult to determine which panel method to use and the optimal number of panels during the trial production stage of a new product. According to product characteristics (such as product structure limitation, peripheral interface height limit, position limit and other factors), PCB design engineers give priority to meeting product structural requirements during design, and then feedback board utilization and production during PCB board making and SMT processing. efficiency issues. After the PCB board is selected in the production process, thermal expansion after encountering different geometric dimensions and PCB assembly methods directly affects product reliability and performance, which increases the processing difficulty and manufacturing cost of SMT production. Combined with the experience of SMT process engineers for many years, the use of jigsaw puzzles to improve the efficiency of SMT production lines has the following aspects to share with you:
In the SMT production line, in order to improve the utilization rate of the production line, there are two common ways of combining boards: AAAA or AB. We can’t directly ask which way is better? This should be considered from the process complexity of the product, the balance rate of the placement cycle of the production line machine after panel assembly, the problem of large-volume components falling after the second remelting, and so on.
The advantage of the positive and negative spelling design (AABB spelling) is to make the equipment configuration and process flow of the SMT production line simple and easy. One stencil, one set of placement program and SPI/AOI inspection program, one time optimization of reflow soldering furnace temperature curve, etc., to improve the speed of SMT fast line change and complete the first article check at one time, and produce PCBA finished products in a very short time Out to the next process function test.
The disadvantage of the positive and negative spelling design (AABB spelling) is that if the component layout of the BOT side and the TOP side of the product is quite different (the main chip is large in size, the component layout density is high, the through-hole reflow component pins exceed the board surface, etc.) It will lead to poor and unstable solder paste printing at the fine-pitch position, and the risk of component dropout during the second pass for components with large volume and weight. Not only does it fail to solve the problem of efficiency improvement in mass production, it will also bring processing difficulty and quality problems. This is also a test of the engineer’s online technical research ability.
(AAA/BBB spelling) Non-front and back spelling design is more suitable for most factories at present. It is easy to deploy the production line and arrange equipment resources reasonably. The production process is stable and it is easy to improve the efficiency of the production line. In PCB design, engineers must consider the rationality of the overall layout of the main chip components, large heat dissipation components, and peripheral interface components. The processing plant only needs to arrange the production line reasonably to produce the BOT surface (less component surface) and then the TOP surface (multiple component surface) ), process engineering is easier to deal with when encountering quality abnormalities during processing. Which panelization method is the best to use under the premise of ensuring the straight-through rate in the production process? It is necessary to comprehensively consider factors such as the machine configuration of the SMT production line, the processing capacity of the equipment, and the stability of the process.
In the production process, under the premise of ensuring straight-through, which SMT board method is the best? The processing capacity of the SMT production line, the processing capacity of the equipment, and the stability of the process should be considered comprehensively.
1. Familiar with SMT production line configuration and production principle first:
SMT factory is an example
Maximum size of PCB production line: 774mm*710mm
NXT can be packaged in the smallest package of 03015, 01005 components
The design capacity of NXT model group is 35000 element/H
AIM multi-design machine management capacity is 27000 global/H
2. The single-sided SMT decal board product is 6 decal boards. When pasting, the original 6 decal boards are optimized to 12 decal boards, which reduces the number of times and frequency cycles of the boards, and increases the output.
3. The machine configuration of each SMT line is different. The equipment engineer balances the speed of each machine when changing lines, the speed of the printing machine, the speed of SPI solder paste inspection, the speed of sheet material, reflow speed, AOI test speed, optimize The whole production line is fully automated and high-speed production, which greatly improves the utilization efficiency of the machine.
All in all, high-quality, low-profile, high-efficiency production is our pursuit and goal of continuous improvement. The chip machine is produced once an hour, which is a very important link in PCB assembly:
The size of one side of the veneer is less than 80mm and needs to be spliced
PCB maximum size (L) 300-350mm * (W) 200-250mm
When the shape of the board edge connector between multiple boards exceeds the interference, it can be solved by the method of rotating board + processing side to prevent collision damage after welding during transportation or handling and poor quality.
When some irregularly shaped PCBs have a large hollow area, in the SMT production process, it is easy to cause the PCB sensor on the conveyor belt to identify incorrectly, resulting in incorrect actions or when the PCB is not detected, stacking occurs, increasing the plate-making time. The process allowance, fill in the blank position
After assembly, it is necessary to ensure that the reference point of the large board is at least 3.5mm away from the edge of the board, and the reference point should not be placed symmetrically, so that the device can pass the self-identification function of the device.
The number and placement of connection points between the slats is also important during the gluing design process.
There is a big difference between FPC and rigid-flex board, and the board needs to be considered more.
In general, the design of particleboard meets the problems of board utilization and production and processing efficiency, and at the same time, the problems of thermal deformation of PCBA after production furnace and board splitting efficiency must also be considered.