Analysis of PCB Warpage and Twist in Laminator Production
Symptom: the base material is warped or twisted before, after or during processing. Hole inclination after soldering is also a sign of base material warping and distortion.
Inspection method: float welding test may be used for incoming inspection. Soldering tests with a 45 degree tilt are particularly effective.
1. The material warps or twists at the time of receipt or after sawing and shearing, which is usually caused by improper lamination, improper cutting or uneven laminate structure.
2. Warpage can also be caused by improper storage of materials, especially when the paper base platen is placed vertically, it will be arched or deformed.
3. The cause of warping is that the copper wall and iron wall foils covered are not equal. If one side is 1 ounce and the other side is 2 ounces, the electroplating layer is not equal, or the special PCB design causes copper stress or thermal stress.
4 If the fixture or fixing is improper during soldering, the heavy components in soldering operation will also cause warping.
5. In the process of processing or soldering, the hole displacement or inclination on the material is caused by improper curing of the laminate or the stress of the base material glass cloth structure.
terms of settlement:
1. Straighten the material or release the stress in the oven, and cut off according to the tilt angle and plate heating temperature recommended by the laminate manufacturer. Contact the laminate manufacturer to ensure that the substrate with unbalanced structure is not used.
2. Store the materials flat in the loading cardboard box or lay the materials flat on the shelf at an angle. Generally, the materials shall be placed at an angle of 60 degrees or less with the ground.
3. Contact the laminate manufacturer to avoid unequal copper foil on both sides. Analyze the plating and stress, or local stress caused by heavy components or large copper foil area. Redesign the printed circuit board to balance the area of components and copper. Sometimes, most of the wires on one side of the printed board are laid vertically with the wires on the other side, so that the thermal expansion on both sides is not equal, causing distortion. Whenever possible, such wiring should be avoided.
4. During soldering operation, printed boards, especially paper-based printed boards, must be clamped with clamps. In some cases, heavy components must be balanced with special clamps or fixtures.
5. Contact the laminate manufacturer to take any recommended post curing measures. In some cases, the laminate manufacturer may recommend another laminate for more stringent or special applications.