In the process of reflow oven and wave soldering machine, PCB board will be deformed due to the influence of various factors, resulting in poor PCBA welding. We will simply analyze the cause of the deformation of PCBA board.
1. Temperature of PCB board passing furnace
Each circuit board will have the maximum TG value. When the temperature of reflow oven is too high, higher than the maximum TG value of the circuit board, the board will soften and cause deformation.
2. PCB board
With the popularity of lead-free technology, the temperature of the furnace is higher than that of lead, and the requirements of the plate are higher and higher. The lower the TG value, the more likely the circuit board is to deform during the furnace, but the higher the TG value, the more expensive the price.
3. The thickness of the PCBA board
With the development of electronic products towards small and thin direction, the thickness of the circuit board is becoming thinner. The thinner the circuit board is, the deformation of the board is more likely to be caused by high temperature during reflow welding.
4. PCBA board size and number of boards
When the circuit board is reflow welded, it is generally placed in the chain for transmission. The chains on both sides serve as support points. If the size of the circuit board is too large or the number of boards is too large, it is easy for the circuit board to sag to the middle point, resulting in deformation.
5. The depth of the V-Cut
V-cut will destroy the sub-structure of the board. V-cut will Cut grooves on the original large sheet, and the excessive depth of THE V-cut line will lead to the deformation of the PCBA board.
6. The PCBA board is covered with uneven copper area
On the general circuit board design has a large area of copper foil for grounding, sometimes Vcc layer has designed a large area of copper foil, when these large areas of copper foil can not evenly distributed in the same circuit boards, will cause uneven heat and cooling speed, circuit boards, of course, also can heat bilges cold shrink, If the expansion and contraction can not be simultaneously caused by different stresses and deformation, at this time if the temperature of the board has reached the upper limit of TG value, the board will begin to soften, resulting in permanent deformation.
7. The connection points of layers on the PCBA board
Today’s circuit board is multi-layer board, there are a lot of drilling connection points, these connection points are divided into through hole, blind hole, buried hole point, these connection points will limit the effect of thermal expansion and contraction of the circuit board, resulting in the deformation of the board. The above are the main reasons for the deformation of PCBA board. During the processing and production of PCBA, these reasons can be prevented and the deformation of PCBA board can be effectively reduced.
Post time: Oct-12-2021