Share the reasons for warping of PCBA and PCB components

发表时间:2023-02-26 22:14

Have you noticed that some boards are not flat after assembly? Or is the bare board you received not completely flush? PCB warping is a generic term used to describe an irregular PCB shape, independent of the shape itself (bent, bent, twisted, etc.). One major difficulty is that a board may transition from flat to warped during the welding cycle, so it cannot always be held by hand. Therefore, the original shape may not be directly related to the shape of the PCB after welding. Warping in PCBS and PCbas can cause problems during assembly or final implementation. We'll discuss in depth what causes both of these conditions and how to prevent them.


PCB warping

When the bare PCB is filled, it goes into the picker, which places the component on top of it in preparation for the welding process. When using warped plates, this unevenness can result in improper placement or falling parts. The flatness of the circuit board is also important when passing through the reflow furnace. These machines heat the board to high temperatures, which can alter the material and warp the board. This can also cause parts to slip, be placed incorrectly, weld Bridges, or other welding problems.

PCB warping can result in poor quality and acceptability of the final product. Ensuring the board's smoothness is critical to preventing assembly-related problems, including bridging or connector open-circuit problems, that can ultimately cause product failure.

Cause and prevention of PCB warping

A PCB consists of different substrate layers that allow voltage and signals to pass through. The processing shop uses many materials suitable for our industry. These materials have good thermal stability, ionic mobility resistance, low dielectric constant, good workability and no substrate drift. Current PCB manufacturing technology ensures that PCB warpage is kept below 0.5% in all states during PCB assembly.

The welding process is probably the biggest catalyst for plate warping. In reflow furnaces or wave welders, PCBS are exposed to high temperatures, causing the material on the board to expand and contract. Due to the different expansion coefficients of copper and base metal, there may be unequal expansion and contraction between the two, resulting in the generation of internal stress. As a result, the plate may warp as it cools and stabilizes to its resting state. Incorrect storage and handling can also lead to warping. If the board absorbs water, it may cause the area to heat and cool at different rates, which can lead to warping.

Other factors that can cause plate warping may be the actual design. During the design process, engineers must consider the balance between the area of the circuit and the pattern of the conductors, as well as the symmetry of the stack of the boards. It may also work if the PCB is operating at temperatures above the rated temperature. Finally, PCB products undergo many thermal drifts and heat treatments in the manufacturing process. When the treatment temperature exceeds the Tg of the copper-clad sheet, the manufacturer must heat both sides of the substrate evenly and evenly while keeping the treatment time as short as possible to reduce the warping of the substrate.

Conclusions on warped PCBS

Bent PCBS can cause problems when picking up and placing components. The SMT component will not land on the intended pad, the component will not enter the intended hole in the plate, the component may slip off, or the solder may bridge and short out. Irregular PCbas cannot be installed into the chassis, which may cause reliability problems on site. All of this makes it important for all stakeholders to do their best to avoid PCB warping. To eliminate this problem, make sure the boards come from a quality store, and pay attention to the handling and storage of the boards in the warehouse, especially in wet places. In addition, engineers can take care to ensure the balance of the plate in the design, or they can specify materials with higher Tg, so that the plate can better withstand different stresses. The PCB factory explained that the engineers shared the cause of PCBA and PCB components warping and the solution of PCBA and PCBA warping.