AMD device packages must be placed accurately according to their geometry outline. Positioning packages manually via hand mounting is not recommended. Typical component placement accuracies of ±50 μm can be achieved using standard pick and place equipment with vision system. The PCB and components are optically checked and measured by the pick and place vision system. The pick and place machine detects the fiducial on the PCB immediately before the placement of the Versal device. Recognition of the packages is performed by the vision system, to ensure correct centering of the Versal device placement on the PCB pad array.
BGA packages with solder balls can self-align during reflow because high solder surface tension pulls and centers the device, allowing a slight placement offsets. For guidance, the maximum tolerable offset of device placement is around 30% of the pad diameter on the PCB for typical non-solder mask defined pads. This means that the misalignment of solder ball device packages to the PCB pad must be better than 150 μm to assure a robust mounting process. Generally, this is achievable using a wide range of modern pick and placement systems. The following setup conditions are important for the pick and placement systems:
- Select the pick and place nozzle type based on the dimensions of the Versal device. The nozzle needs to firmly hold the device package during the pick and place stage. Choose the appropriate nozzle type for the device package from the manual provided by the pick and place equipment manufacturer.
- Use the ball recognition capabilities of the placement system and avoid package outline centering. This eliminates the solder ball to package edge tolerances of the package. Refer to the specific package outline drawing for details.
- Use a suitable lighting system and select the correct features of the measuring method before placement to ensure proper package identification during vision recognition. Choose the most suitable settings from the manual provided by the pick and place equipment manufacturer.
- To avoid solder bridging or solder smear, ensure the proper placement force of the device package during placement on the PCB. Excessive placement force can lead to excess solder paste and cause solder bridging. However, even slight placement force can reduce contact between package solder balls and solder paste. Poor contact can cause solder defects including open solder joints, off-center packages, or even head-in-pillow (HIP) defects.