Reasons for deformation and Warpage of PCB in SMT

Warpage of PCB in SMT

Abstract: The IPC standard stipulates that the maximum allowable deformation of the circuit board SMT patch processing is 0.75%, and the maximum allowable deformation of the circuit board without SMT patch processing is 1.5%. The calculation method of the circuit board warpage is: (PCB diagonal length * 2) * 100%. Deformation and warping of the circuit board will directly affect the soldering quality, so SMT patch factories are very troubled by this problem. To meet the quality requirements of high-precision SMT patch processing, many SMT patch factories have very strict requirements on circuit board deformation and warpage. So what is the reason for the deformation and warping of the circuit board SMT patch processing? Next, SZTech-SMT will share with you, hoping to bring you some help!

Analysis of the causes of deformation and Warpage of PCB SMT patch processing

1. V-Cut on the circuit board is generally the main cause of deformation and Warpage of PCB, because V-Cut is to cut grooves on the original large board to obtain small boards, so the place of V-Cut is prone to deformation;

2. Different circuit boards will have the maximum heat resistance value. When the reflow temperature is higher than the maximum value of the board. It will cause the board to soften and cause deformation and warping.

3. After the general circuit board SMT patch processing is completed, it will be directly transported through the reflow soldering equipment track. If there are overweight parts on the board or the size of the board is too large, and the reflow temperature is high, it will show a concave phenomenon in the middle due to its weight and heat, resulting in bending deformation.

4. Electronic products are developing in the direction of small size and lightweight, and the thickness of circuit boards is also getting thinner and thinner. The thinner the circuit board, the easier it is to deform at high temperatures.

5. Generally, a large area of copper foil is designed on the circuit board for grounding. When these large-area copper foils cannot be evenly distributed on the same circuit board, it will cause the problem of uneven heat absorption and heat dissipation speed, and warping deformation will also occur after cooling;

6. Since a lot of circuit board incoming materials are not in the original packaging, due to the environmental problems of storage, there will be more or less moisture in the circuit board. If there is no baking operation before the SMT patch processing of the circuit board, the water will evaporate when the high temperature of the reflow soldering occurs, resulting in deformation and warping;

The solution to the deformation and Warpage of PCB SMT patch processing

1. Most SMT placement factories use reflow soldering tracks to transfer circuit boards. First of all, we try to use the long side of the PCB as the contact with the track, which can reduce the weight of the circuit board itself. Thereby avoiding deformation and warping of the circuit board.

2. If the above point 1 has not been improved, the problem of deformation and warpage can also be solved by using the form of the tray passing through the mesh belt of the reflow furnace;

3. If the circuit board is deformed during SMT patch processing and reflow soldering, it is necessary to measure the cost and production batch to make a jig to assist in the completion.

4. If the circuit board is not in the original packaging, it needs to be baked at 120 degrees Celsius/4 hours before SMT patch processing to avoid deformation and warping during reflow soldering due to the presence of moisture;

5. Since the V-Cut will destroy the structural strength of the PCB board between impositions, try not to use the V-Cut sub-board, or reduce the depth of the V-Cut. Or give relevant departments improvement suggestions, and propose to use stamp holes to connect the imposition.

The above content is provided by SZTech-SMT for you. To learn more about SMT chip processing, please visit www.SZTech-SMT.com

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