During reflow soldering and wave soldering of PCBA board, due to the influence of various factors, PCBA board will deform, resulting in poor PCBA welding, which has become a headache for production personnel. Next, we will analyze the causes of PCBA plate deformation.
1. Passing temperature of PCBA plate
Each circuit board will have the maximum TG value. When the temperature of reflow soldering is too high and higher than the maximum TG value of the circuit board, it will soften the board and cause deformation.
2. PCB board
With the popularity of lead-free technology, the temperature of passing through the furnace is higher than that with lead, and the requirements for plates are higher and higher. The lower the TG value, the easier the circuit board is to deform when passing the furnace, but the higher the TG value, the more expensive the price is.
3. PCBA plate thickness
With the development of electronic products in the direction of small and thin, the thickness of circuit board is becoming thinner and thinner. When reflow soldering is over, it is easier to cause the deformation of the board under the influence of high temperature.
4. PCBA board size and quantity
During reflow soldering, the circuit board is generally placed on the chain for transmission, and the chains on both sides are used as support points. If the size of the circuit board is too large or the number of panels is too large, it is easy for the circuit board to sag to the middle point, resulting in deformation.
5. Uneven copper laying area on PCBA board
Generally, a large area of copper foil is designed on the circuit board for grounding. Sometimes, a large area of copper foil is also designed on the VCC layer. When these large areas of copper foil cannot be evenly distributed on the same circuit board, it will cause the problem of uneven heat absorption and heat dissipation speed, and the circuit board will naturally expand and contract with heat, If the expansion and contraction cannot be carried out at the same time, it will cause different stresses and deformation. At this time, if the temperature of the plate has reached the upper limit of TG value, the plate will begin to soften and cause permanent deformation.
6. Connection points of each layer on PCBA board
Today's circuit boards are mostly multilayer boards with many drilled connection points. These connection points are divided into through holes, blind holes and buried holes. These connection points will limit the effect of thermal expansion and cold contraction of the circuit board, resulting in the deformation of the board.
