Contents
What is exposed pad?
Definition. An exposed pad is an exposed metal plate on an IC package. This application note describes pads that are located on the bottom of the package. The exposed pad is plated with the same metal or metal alloy as the leads of the IC, usually tin.
Why thermal relief pads?
Thermal relief is a technique used by PCB manufacturers to thermally separate soldering pads from large copper areas, to prevent excessive heat transfer from the pads during the soldering process, which would result in delayed melting of the soldering alloy or even no melting at all.
What is EPAD PCB?
It stands for exposed pad. They’re intended for PCB heatsinking; you solder it to a large copper plane to pull heat away.
Are thermal pads better than paste?
The big advantage to thermal paste is its ability to be easily spread. It will conform to uneven surfaces very well, and fill large gaps more evenly than thermal pads. Another advantage is that with the ability to apply it as a thin layer, thermal paste can provide better thermal conductivity then the thicker pads.
Do you need thermal pads?
Yes, they do. Although the heat transfer they offer may not be as good as CPU grease, applications like RAM and VGA cards require thermal pads only.
How do you solder a pad on an IC?
Solder or at least flux the pad on the IC and solder just the corner pins to the PCB. Put a 60 watt or so solder iron with a small chisel tip into the back of the PCB and into the hole you drilled.
What’s the best way to heat a solder pad?
Apply paste first, if you have it, or a little bit of wire solder to the pad. Then pre-heat. The pre-heat temperature is around 125C or so. Once everything is heat soaked at 125C, apply localized hot air directly to the part to be soldered and immediately around it.
What happens when you solder a small part?
Often, you will notice the part kind of self-aligns itself and snaps into place when the solder is all melted. This is a good indication that it is hot enough. Small parts will probably reflow much faster than large parts, and may not need as high a temperature either. Your first efforts may not work well.
Is it safe to drill a hole in an IC?
However IC’s that have a bottom pad for grounding and/or heat sink normally have no hidden traces under them. At most there would be a grounding pad with a ring of SMD capacitors around its perimeter. Unless it is very small it is still safe to drill a small hole in the center.