# SMD diodes suitable for hand soldering

I have done a fair amount of soldering with SMD components now. I can solder an 0402 size component I prefer not to. I can solder an 0603 just fine and anything bigger. But my question is, what diode packages are similar in size to an 0603 but no smaller. I am not very familiar with diode SMD packages. I am aware different applications require require different size packages for power reasons. I am concerned with board space for my application and my ability to solder them by hand.

I will need a small signal diode package(s) in the 0603 size range. I will also need the around about recommended package(s) for dissipating ~100 mW continuously.

I am aware diodes come in MELF packages but this limits my options for zener devices and increases cost (sometimes).

So far, it seems SOD123 is my best option for diversity of zener devices. I am hoping to find something slightly smaller.

I also know diodes come in SOT (TO) style packages I am not very familiar with these devices but its more familiar than SOD, SM() and other diode (device) packages I am not familiar with at all.

• SOD-523 is somewhere between 0402 and 0603. MELF stands for Most End up Laying on the Floor. – Nick Alexeev Oct 3 '17 at 3:58
• I prefer pairs of diodes packaged in SOT-23, BAV99 for instance, and there's a package SOT-323 that's one smaller than that. Diodes are frequently used in multiples, and if only one is needed, they're cheap enough to waste. – Neil_UK Oct 3 '17 at 4:03
• BAV99 is perfect I like it. Love the idea of getting two or even three diodes for the price of one. – minimer Oct 3 '17 at 4:18
• SOT23 is the way to go for smallish diodes, particularly when hand soldering, because you will not get it the wrong way around... Small symmetrical 2 pin packages are boring for diodes by hand because sooner or later you will get one backwards (and it is usually on a really dense board). – Dan Mills Oct 3 '17 at 11:30

I will need a small signal diode package(s) in the 0603 size range. I will also need the around about recommended package(s) for dissipating ~100 mw continuously

SC-70 is about the same size as 0603, but it is fussier to solder because there are up to 6 pins on it. To dissipate 100 mW you'll want a bigger package anyway.

• I like the SOT-363 SC-70 packages that was exactly what I was looking for. I was hoping to only make one footprint. Because I am lazy. But it turns out all the zeners i need come in SOT-23 packages. I will only need to create the footprint for SOT-363 landing. I know from experience I can get better thermal transfer with more pads instead of larger plastic volume. – minimer Oct 3 '17 at 4:17
• FWIW, the first SC-70 part I check out was rated for 200 mW, but with 625 C/W $\theta_{ja}$, which just seems a bit much for continuous 100 mW operation. Why not just do all SOT-23? A single diode SC-70 isn't going to have 6 pins, but the pins will be sized to allow 6 in other variants. The SOT-23 pins will be thicker and wider, so $\theta_{ja}$ is about half of the SC-70. – The Photon Oct 3 '17 at 4:28

SOD123, which you mentioned above, and SMA, are probably the most common, and fairly easy to hand solder.

There is also the D2PAK (TO-263-3), which is easy to solder but possibly too big for your purposes.

You can find some diodes in standard 0805/1005/1206 packages but these are more rare and often a bit pricier than the alternatives noted above. Same for MELFs; more rare, more expensive, plus frustrating to handle.

A diode array in an SOT-323, as mentioned above by Neil_UK, is an elegant and low-cost solution.