This is just one article in a series of articles discussing design for manufacturability for electronic assemblies. As a contract manufacturer we see every possible design decision you can imagine. We know what works, and we know what doesn't. We're happy to look at your assembly for any manufacturability concerns, whether we're building the assembly or not. Surface Mount Technology (SMT). The single greatest thing to happen to the manufacturability of electronics since the printed circuit board itself. Rule number 1 of DFM for electronic assemblies
"Whenever possible, use surface mount components instead of thru-hole components."
There are exceptions of course, but generally speaking surface mount components are almost always easier to assemble than thru-hole components. Primarily, this is because of the equipment that most electronics manufacturers employ. Even if your contract manufacturer has fully automated thru-hole equipment, it's likely still easier for them to assemble your design using surface mount components than it is thru-hole components. Today, the fastest SMT machines can pick and place components as fast as 120,000 times per hour. The fastest thru-hole machines still pale in comparison at 26,000 components per hour, and thats only for axial components. Radials are even slower to assemble at 22,000 components per hour.
Remember, time is money when it comes to assembly work. Your manufacturer is charging you for their time. So if he can assemble your board at 120,000 CPH instead of 22,000 CPH, he's going to be able to deliver your product sooner and you'll be saving money.
But placing/inserting the components is only half the battle. You still need to solder it. With surface mount components, all of the soldering is done automatically using solder paste and a reflow oven. Thru-hole components need to either be wave soldered (if designed properly), selectively soldered (if designed poorly), or *gasp* hand soldered (when you really just didn't even think about manufacturability). Talk about taking a long time. Thru-hole soldering is not as easy as it might seem. Yeah one or two joints here or there can be pretty easy. But to solder thousands of solder joints by hand, consistently, year after year, takes a special person with a lot of skill and experience. And those people don't come cheap. Machines on the other hand, while the initial investment is high, are very cheap compared to a competent soldering technician. Time is money.