- the solder quantity
- the width of the pad
- the length of the pad
- the solder flow at the pin foot
- flow behavior on the pad
- the height of the pin.
- The field of view (FOV) of the angled view is responsible for the inspection speed of the complete system. As a comprehensive use of the angled view is necessary for the inspection of complex PCBs with a high number of ICs, the FOV is decisive for the time of inspection.
- The depth of focus and the image quality of the angled view is also decisive for the whole FOV on the PCB as well as in regard to the height extension of the components. Consequently, it influences the inspection quality and speed.
- The sole evaluation of the front menisci at pin solder joints has only a limited informative value regarding the solder quality. An angled inspection of the IC pins enables an optical inspection that resembles an IPC-conform test much more.
- Especially for the inspection of fine pitch ICs up to 0.3mm a sufficient resolution is necessary for safe fault detection.
- If there are higher components in front of the tested pins there might be overlaps in the angled field of view. One tries to evade this situation with design regulations, however, this is a question of practicability.
- A deflexion of the PCB during the inspection process might cause a displacement of the inspection positions in the camera image of the angled-view. To counteract this effect adequate compensation algorithm can help.
- Components in an angled position other than the 90°-steps cause extremely higher efforts regarding the programming time, because the test samples that are defined in the library (test units, macros etc.) can ot be used and a manual adaptation is necessary.
- Besides the image capturing using angled view, an intelligent verify function is necessary in order to reach a safe fault detection with minimum false call rate under the above named circumstances.
- 1. For components in different angular positions (e.g. 20°) no adjustment of the inspection position or the parameters is necessary as the viewing direction has only to be adjusted to the respective angular position (e.g. 20°), and the inspection can be carried out using a standard library sample in 0° position.
- 2. If the viewing direction is obstructed by components, it is possible to turn the viewing direction for a few degrees until the solder joints are completely visible. Consequently, a safe fault detection is guaranteed.
