I’ve laid out a breakout board for this self-contained switching power module: https://www.ti.com/lit/ds/symlink/lmz14202ext.pdf
But I’m not sure what to do about the “exposed pad”. I don’t see how I heat it up enough for the paste (with the Hakko FX-888D or the hot air station), so should I just plan on applying some thermal grease? Conductive epoxy?
Should I put a plated through hole in the middle of the pad and get at it that way?
It says the “exposed Pad” should be connected to GND, so thermal paste is not an option.
The most used option is to apply solder paste and heat the whole PCB and parts in an oven hot enough to solder everything in one go.
For hobby-level sometimes a big hole (2 or 3mm) is sometimes made in the PCB so you can heat it with your soldering iron from the underside.
I use 1 or more holes in the EP for ICs with which I cannot extend the pad out beyond the edge of the IC body. Put flux on the IC EP. Poke the hot soldering tip into the hole(s). Use high temp and wait for the solder to “suck in.” For this chip, the holes might be good. But another possibility:
Extend the pcb pad by 1-2 mm beyond the edge of the IC body. Put a thin layer of solder on the pcb center pad area before mounting the IC and apply flux to the extended pad on the IC . When soldering the chip, use a relatively powerful soldering iron (50W?) with a large screwdriver tip and heat the extended board area of the pad using some solder.to couple the soldering heat.
I use the paulvdh method
I have a “toaster oven” (used $5, new $50). Use solder paste. I set the oven to broil and watch through the window to see when the solder turns from gray to silver. The little pads heat first then 30 seconds later the large pads heat. Turn off the power, open the door and do not touch until all the solder cools. Some times I add a extra large pad with no part (just paste) to see when the board is hot enough.
I also have a hot air solder gun that will heat only a small part of the board.
I’ve used hot air to solder ICs with exposed pads. Put a little bit of solder paste on the pads, use the hot air to warm the board from the bottom, then finish by heating the IC and the top of the board until the solder paste reflows.
I’m putting a hole in the pad, since I’m at liberty with the breakout design. Thanks for all the assorted suggestions.
I’m intrigued by oven-based solutions but so far haven’t had enough reason to set up that way. Since I’m having my SMT assembled by JLC, I’m only doing one or two devices at a time for rework, breakouts, or where I have to provide the component myself so the hot air station is just right.
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