Some Problems in the Design and Processing of PCBA Board
For most circuit boards, how to set the number of panels for PCBA board processing? What factors need to be considered? How to add circuit board can improve production efficiency and reduce the loss of circuit board Since splicing has so many advantages, the PCB design engineer can design the circuit board after determining the PCB shape Then PCB jigsaw is a problem to be solved in PCB processing
Common methods for connecting circuit boards: There are many methods for connecting circuit boards, such as 2-in-1, 3-in-1, 4-in-1, etc. The more common method is to combine more than two pieces of the same circuit board into a large circuit board; The circuit boards with different shapes can also be assembled, but the application is relatively small, mainly because the number of circuit boards with different shapes is difficult to match in the production process; The positive and negative electrodes of similar circuit boards are combined into a circuit board. The positive and negative electrodes can improve the processing efficiency of SMT chips and are suitable for circuit boards with fewer components. The male and female board design is not applicable to all circuit boards. If a heavy component is designed on one side of the circuit board, the use of a male and female board may cause the heavy component to fall off when it is used as a second component. The plate with large area of heat absorbing elements cannot be designed with Yin Yang plate. The disadvantage of male and female plates is that SMT processing is limited, which is easy to lead to uneven heating. It is necessary to consider various factors in the specific splicing pipeline.
The influence of board making cost on the number of puzzles
Board making cost is the most important factor to measure the number of puzzles. In order to improve production efficiency and reduce costs, circuit board manufacturers will have basic standard board sizes. These standards repeatedly consider the optimal utilization of circuit boards. Common standards are 16.16 "x16.16", 18.32 "x18.32", 20.32 "x20.32",... The cost of the circuit board will be affected by the size of the circuit board used. Selecting the most appropriate standard board to achieve the best utilization of the board can reduce the production cost of the circuit board. The cost of the circuit board is also related to the number of layers of the circuit board, the number of holes and whether there are blind holes and buried holes.
SMT processing line is divided into long line and short line according to different requirements. Short term lines can have at most two fast patch machines and one slow patch machine; Long term production lines usually have multiple fast and slow placement machines. Usually, each production line is equipped with solder paste printing machine. It takes about 35-40 seconds to brush solder paste on a 150 mm long circuit board. The two in one circuit board is processed in a short period of time in SMT. The time allocated for each machine is about 10-26 seconds, and the placement time is far less than the solder paste printing time, indicating that the placement machine is waiting for the solder paste printer, and the production capacity of the placement machine is not fully utilized. Replace 2-in-1 with 4-in-1, and the efficiency will be improved immediately
PCB factories usually hope that the smaller the number of panels, the better, because the smaller the number of panels, the less opportunities for X-Board, which can reduce the scrap rate and reduce the cost of circuit Board manufacturing SMT factories also don't like to play the X board, because clicking the X board will reduce the processing efficiency Therefore, we still need to calculate the most affordable number of panels from the perspective of the overall processing cost of PCBA The process capability of PCB factory SMT factory also has an impact on this In addition, consider whether to use the V-cut or Router process to remove the edges of the circuit board This also affects the panel design
How to control the quality of PCBA processing? Now let's also introduce it!
The manufacturing process of PCBA involves many links. In order to produce good products, the quality of each link must be controlled. General PCB board consists of a series of processes, such as PCB board manufacturing, component procurement and inspection, SMT chip processing, parts processing, program startup, testing, aging, etc. Let's carefully explain the key points to be paid attention to in each link. 1. After receiving the PCBA order, PCB board is manufactured, Gerber files are analyzed, and the relationship between PCB hole spacing and board bearing capacity is noted, so as not to cause bending or damage. Whether high frequency signal interference, impedance and other key factors are considered for wiring. Procurement and inspection of components. The purchase of parts and components requires strict control of access, must be purchased from large traders and original manufacturers, and 100% avoid second-hand and counterfeit data. In addition, a professional incoming material inspection post has been set up, and the following items have been strictly inspected to ensure that there is no failure of components. Reflux furnace temperature test, no flying wire, whether the through-hole is blocked or leaked, whether the plate surface is bent, etc.; IC checks whether the silk screen is completely consistent with the BOM, and maintains constant temperature and humidity;
Other commonly used data: check silk screen, appearance, electricity measurement, etc The inspection items shall be carried out according to the sampling method, and the proportion is generally 1-3% SMT assembly processing: Solder paste printing and reflow furnace temperature control are the key It is very important to use high quality laser dies that meet the process requirements According to the requirements of PCB, some wire mesh holes need to be expanded or reduced, or U-shaped holes are used to make wire mesh according to process requirements The temperature and speed control of reflow soldering furnace is very important to solder paste penetration and welding reliability It can be controlled according to normal SOP operation guidelines In addition, AOI testing needs to be strictly implemented to minimize defects caused by human factors DIP parts processing In the process of welding, the design of wave soldering die is the key How to use the mold after the furnace to maximize the product quality is a process that PE engineers must constantly practice and summarize experience In the previous DFM report, you can suggest to customers to set some test points (Test Points) on the PCB The purpose is to test all components of PCBA circuit after being welded on PCB If you have conditions, you can ask the customer to provide a program, and burn the program into the main control IC through a burner (such as ST-LINK, J-LINK, etc.), so that you can test the effects of various touch actions more intuitively Function change to verify the functional integrity of the entire PCBA The main test content includes ICT (In Circuit Test), FCT (Function Test), Burn In Test (aging test), temperature and humidity test, drop test, etc, Operate test plan according to customer requirements and summarize report data