Shortwave or Medium-Wave? Picking the Right IR Heaters for Your SMT Line
If you’re staring at your SMT setup and trying to decide between shortwave (SW) and medium-wave (MW) infrared lamps, it really comes down to two things: how deep you need the heat to go and how fast you need your boards moving. Both use quartz tubes, but they behave very differently once you flip the switch.
Let’s talk about the physics (the simple version)
Shortwave lamps run hot. Really hot. Because of that, the energy they pump out actually sinks deep into the PCB and the components. It’s like a shot of espresso for your ramp-up time—it happens fast. Medium-wave lamps are a bit more laid back. They operate at lower temperatures, and the energy tends to hang out on the surface, getting absorbed quickly by the solder paste and the top of the board. Here is the rule of thumb: if you’re dealing with chunky, high-mass components, go withSW. It gets the job done. But if you’re working with thin boards and you’re worried about scorching the top layer before the bottom even warms up,MWis your best bet.
A word on quartz and heat
We use high-purity quartz for a reason. These things go through a lot of thermal shock—heating up and cooling down rapidly—and cheap glass would just crack. The quartz lets the IR radiation slide right through without soaking it up. But here’s the catch. High-wattage SW tubes put a massive amount of heat on your chassis. If you pack in a high-density SW array, you can’t skimp on the cooling. Make sure your fans and heat sinks are up to the task. If they aren’t, you’ll end up frying the lamp ends and burning out your filaments way too soon.
Making it work on the line
Usually, the decision comes down to how much space you have and how fast you want your conveyor running. SW lamps let you keep the heating zone small and the belt moving quickly. With MW, you’ll need to slow things down to give the board enough dwell time to hit that liquidus temperature. But be careful. Speed is great, but SW can be a bit too aggressive for sensitive parts. It’s an intense heat. MW is much gentler. My advice? Don’t just guess. Map out your thermal profile first. It’s much better to spend a few hours tweaking the profile now than to realize later that you’re blowing right past your peak temperature and ruining your boards.