● Pad size
When purchasing component, the buyer should learn from the experience of solder technician, taking the costs and maintenance’s expectation for replacement into account. Conventionally, the fragile, perishable, unstable components mounted on an expensive PCB board should be replaceable to avoid abandoning an entire board for simple components. Namely, component replaceability plays a vital role especially for high-priced PCB boards. Thus we’d better acquire some knowledge of component replaceability.
Actually, component replaceability is mainly determined by the pad diameter and the ratio between component and pad. If the pad size is not enough, the heat balance between the component and the pad will be broken. This will cause the adhesive which fixes the pad /copper on the board dissolves and the pad will be separated from the board. It’s really regretful to get such a result of damaging the board, making it useless at all. On the contrary, if the pad size is too big, the expense will be high accordingly. Hence, adequate pad size, neither too large nor small one is the best.
Besides, heat is also a influence factor as it will be destructive if not adequately dissipated. However, the heat is required to be sufficient, but not excessive, or either the pad or component may be damaged.