Context: Through-hole manufacture adds to board cost by requiring many holes to be drilled accurately, and limits the available routing area for signal traces on layers immediately below the top layer on multi-layer boards since the holes must pass through all layers to the opposite side. Once surface-mounting came into use, small-sized SMD components were used where possible, with through-hole mounting only of components unsuitably large for surface-mounting due to power requirements or mechanical limitations, or subject to mechanical stress which might damage the PCB.

Question: Which type of construction is more expensive?
Answer: Through-hole

Question: What type of boards end up with limited routing space in through-hole manufacture?
Answer: multi-layer

Question: What force might damage a PCB if large components are surface mounted?
Answer: mechanical stress

Question: What components can be surface mounted to save space?
Answer: small-sized SMD components

Question: A component might not be able to be made any smaller because of its mechanical limitations or what other need?
Answer: power requirements

Question: What will not damage the PCB?
Answer: Unanswerable

Question: Mechanical signs will damage the what?
Answer: Unanswerable

Question: What increases the available routing area?
Answer: Unanswerable

Question: Large-sized SMD components were used when?
Answer: Unanswerable