X-ray Inspection for FOMCM (Fan-Out Multi Chip Module) μ-bump Non-wet

Fan-out (FO) package is one of newest package in assembly industry [1]. Therefore, there are still many unresolved problems that must be solved. One of the main problems are non-wet solder joint. Normally, X-ray is used to detect it [3]. The X-ray can be classified into three main types, namely 2D X-ray, 3D X-ray and CT module X-ray. 2D X-ray is a common machine. It is used to detect by the difference in grayscale caused by the different absorption rate after the Xray penetrates. The principle of 3D X-ray is reconstructed the image by rotating a sample to shoot multiple projections [4]. Thus, the defect can be checked from different angles and voxel resolution is only 40nm leading to the non-wet gap <1 um still can be detect. The principle of CT module X-ray is similar to 3D X-ray. The differences of them are the execution time and resolution. The CT module X-ray suitable for cases that require high speed but cannot be detected by 2D X-ray.From the above, there are respective capabilities of 3 kind of X-ray. $\gt 9.7\mu\mathrm{m}$ non-wet gap can be easy detected by 2D Xray and it is very simple to operating. $\gt 5\mu\mathrm{m}$ non-wet gap can detected by CT module X-ray and the time consumption is about 10 minutes. The 3D X-ray can detected <1 um non-wet gap, but it must be run over 1 hour. In this paper, we confirm the non-wet gap capabilities and use cross-section and SEM (Scanning Electron Microscope) to verify.