PCB News - What are the methods for detecting warpage of circuit board quality defects and related standards

What are the methods for detecting warpage of circuit board quality defects and related standards
Recently, some customers consulted about PCB thick copper plates and asked whether grid copper is better or full copper? In fact, this depends on the size of the billboard. The large board grid copper is good, because the whole copper will keep warping when subjected to external force, but the grid copper will not warp and maintain the original flatness. The purpose of keeping copper on the side of the general process is to ensure the warpage of the board. The IPC standard warpage is less than 0.75% as qualified product. It is said that the warpage of the copper clad laminate is divided into bow and twist. How to calculate PCB warpage? What are the measurement methods? Many beginners and some colleagues who have done circuit boards for several years usually do not understand the problem. PCB board warping will cause inaccurate positioning of components, which will bring a lot of difficulties to assembly and installation work. Help everyone sort out.
If the circuit board is warped, the measurement method is to lay it flat on a marble or glass board, and the four corners of the circuit board are on the ground, and measure the height of the middle arch; the calculation method is: warpage = arch height / PCB long side length *100%.

Place the PCB to be measured on the marble countertop and use a plug gauge to measure it., The standard calculation is:

Here are several commonly used measurement methods:

1. Use a marble or 5mm thick glass plate platform, use a plug gauge to measure the largest size of the corner, and then use a ruler to measure the length of the diagonal and divide by two numbers. If it is greater than seven thousandths, it will not be qualified.

2. Knock the surface of the board with your hands, listen to the sound of the gap between the board and the marble countertop, and then level it with your hand.

3. The optical inspection method uses the principle of light interference to test warpage and distortion. The accuracy can reach 0.1mil. It is often used for mass production and shipment inspection, or for laboratory simulation of reflow soldering for analysis.

Regarding PCB warpage is a problem that many manufacturers have discussed and researched, Chang Dongxin used experiments to find the root cause of the warpage, and fundamentally improved it, improved product quality, and reduced company costs and customer complaints.
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