Even modern printed circuit boards may need through-hole components. Buyers need to know whether their contract manufacturer can give through-hole work the attention it deserves when the manufacturer's business model revolves around surface mount technology (SMT).
The SMT business model appeals to mid-size and larger manufacturers because the lines can be almost completely automated. They can run a high volume of boards with little human intervention and therefore low cost per board.
Through-hole assembly is a slower process, whether it's manual or automated. Many contract manufacturers avoid this kind of work because it takes resources away from their preferred higher-volume SMT business.
Buyers and engineers don't have much love for through-hole boards either, since they tend to be larger and more costly to assemble.
So you might think that through-hole technology is old-fashioned and destined to fade away. Indeed, most modern ICs are not even available as a through-hole option.
But through-hole is not going away any time soon. At Z-AXIS, even though only about 20% of the parts we buy are through-hole, nearly 90% of the boards we run are mixed technology: a combination of SMT and through-hole. This is probably the direct inverse of most contract manufacturers our size, who run 80% to 90% SMT-only.
One reason is that nearly half of the board assemblies we produce are for power supplies. A power supply uses capacitors, inductors, and transformers to transfer energy, and the physical size of the component is proportional to the energy it can store. That means we need some fairly large and heavy components, and through-hole technology is almost always needed. A through-hole component's pins, inserted through the board and soldered, help create a much stronger mechanical bond than the solder-only bond that holds SMT components in place.
The rest of our board assemblies, like our power supplies, are usually destined for use in in industrial, medical, or commercial equipment, where there is a premium on reliability. Any customer-accessible connector is likely to be through-hole mounted for additional mechanical strength, so it can withstand repeated stress as cables are connected and removed. For this reason some industrial connector types, such as the BNC, are not even available as surface mount components.
Buyers should understand their contract manufacturers' business model. If your manufacturer is focused on their higher-volume SMT business, it's important to know how they will handle though-hole components when you need them to. They should have adequate resources, a trained and experienced staff, and efficient processes to work with through-hole components at a reasonable cost and ensuring high quality.