Question: Is there an IPC or other specification that exists explaining the minimum shear force requirements for surface mounted components?
Answer: The IPC does not have any specification that discusses the strength or shear forces of solder or components mounted onto pads or into plated through holes.
Based upon best manufacturing and design practices, IPC does have specifications to design circuit pads/land and they use the JEDEC criteria for pad/land size layouts related to individual components. Solder joint strength is based upon many things, such as size of pad/land, amount of solder, excursion through the thermal zone, plating integrity of the component and the board, etc., so it is very difficult to define what the shear strength of a solder joint should be.
What most people do is find a joint that has worked over time and make comparisons to it based upon a DOE. The DOE modifications could be profile temp changes, paste deposition thickness changes, paste material changes, etc.
The reliability of the solder joint is not based upon the how much shear force is required to break the solder joint, but how it is designed for the environment of the operational product. Solder joints typically fail by fatigue from thermal cycling and there are IPC specifications which evaluate thermal cycling, hence it all depends where the product is to be used and the environment it is to be used in.