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What seem to be the most popular SMD diodes currently come in SC-79 packages, but they super tiny and really hard to hand solder...

enter image description here

...and they also can be a hassle even for reflow.

So I thought I'd replace them with easy to solder 0603 equivalent parts, but all the parts I can find on DigiKey have footprints with bottom exposed pins that are even harder to hand solder...

enter image description here

There are also some SOT-23 diodes that would be easy to solder, but are not as easy a swap out because they are a different shape....

enter image description here

Why don't diodes come in normal, easy to hand solder 0603 packages?

Is there some other 2-pin package that they do come in that is easy to solder and is easy to swap out for the SC-79 footprints?

NB: Of course Light Emitting Diodes do come in all manner of nice 0603 packages...

enter image description hereenter image description here

...and for prototypes I have been using them in place of the normal diodes (sometimes the feedback is actually nice!), but it is not always practical to use LEDs in place of a normal diode (if you need a low-drop shottky, for example).

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    \$\begingroup\$ Are you using a hot-air gun? The 0603 with bottom pads are do-able with hot air, although they are finicky due to the small size. A sticky flux helps. \$\endgroup\$
    – rdtsc
    Commented Jun 23, 2016 at 17:38
  • \$\begingroup\$ It appears to me that using soldering tweezers would work, as long as the pads extend out from the component slightly. However, I have no experience with components that small - maybe someone else would be kind enough to comment on if that is a good idea. \$\endgroup\$
    – Andrew Morton
    Commented Jun 23, 2016 at 20:25
  • \$\begingroup\$ I'm with you on this one BigJosh, I used to do this for a living and have often wondered myself, even SC70 packages are easier to solder than those diodes (but not by much) \$\endgroup\$
    – Sam
    Commented Jun 24, 2016 at 0:54
  • \$\begingroup\$ Offsetting the part a little ought to expose enough pad that you can use a regular soldering iron and tweezers. \$\endgroup\$
    – Ian Howson
    Commented Jun 24, 2016 at 1:23
  • \$\begingroup\$ I just recently used that exact 0603 part you link to, and soldered it no problem with an iron exactly the same way as I'd solder an 0603 resistor. I only realized it has bottom pads when I read your question! Contact verified with a multimeter and by the fact that the circuit works. \$\endgroup\$
    – Timo
    Commented Jun 24, 2016 at 10:33

7 Answers 7

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0603 is 1.5 x 0.85 mm.

There are diodes available in "SOD-323" (aka SC-76) package, which is 1.7 x 1.25 mm, pretty close to an 0603. Digikey lists ~250 part numbers, from over a dozen manufacturers, for single rectifier diodes in this package size.

enter image description here

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  • \$\begingroup\$ Don't want to infringe on your domain of answering, but these come up on Mouser when applying 0603 package: nl.mouser.com/ProductDetail/Comchip-Technology/CDSU101A/…; nl.mouser.com/ProductDetail/AVX/SD0603S040S0R2/…; +1 by the way :-) \$\endgroup\$
    – Asmyldof
    Commented Jun 23, 2016 at 17:51
  • \$\begingroup\$ @Asmyldof, Digikey also has ~10 PN's listed as "0603", but most have the pads hidden like the ones OP doesn't like. \$\endgroup\$
    – The Photon
    Commented Jun 23, 2016 at 17:55
  • \$\begingroup\$ I know, which is why I mention Mouser, as Mouser and Farnell regularly supply me with types like the two above. \$\endgroup\$
    – Asmyldof
    Commented Jun 23, 2016 at 20:34
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While Mr Photon manages to perfectly answer the spirit of your question (and by the way, there are many, many diodes that are well doable, but whether "they fit your application", who knows other than you), I felt like adding the literal answer to your question as well:

Because parts in 0603 and similar sized packages are generally not designed for hand-placement or "hobby-shop" grade reflow, but for professional, high volume manufacture.

A small diode with bottom pads may be made, to facilitate the growing need from industry to have reasonable performance in a package that can be jammed right onto the next package without creating shorts.

Imagine your run of the mill 0603 resistor or LED. If you had to place them as close together as possible... how big a gap do you need, even in professional reflow, to guarantee no shorts or solder bridges between the exposed ends? That's pure loss in mobile phones and/or wearable tech.

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    \$\begingroup\$ 0603 package is really not that hard to hand solder once you get the hang of it. The trick is: remove any solder on both pads, put some solder on a pad, solder the first pad while holding the part still, solder the second part and you are done. \$\endgroup\$
    – lucas92
    Commented Jun 23, 2016 at 22:41
  • \$\begingroup\$ For the question, I've soldered something similar and a soldering iron is more than enough. Put lot of soldering on both pads, put the soldering iron on the pad and put the component. You need to put some pressure on the component so it stay still. Put pressure on the other side of the package and put the soldering iron on the other pad and it should be done. \$\endgroup\$
    – lucas92
    Commented Jun 23, 2016 at 22:43
  • \$\begingroup\$ The seems to ask the question "why do they make normal 0603 resistors and capacitors that can not be packed tightly together?" rather than answer the question "why don't they make 0603 diodes can have easy to solder foot prints?" \$\endgroup\$
    – bigjosh
    Commented Jun 24, 2016 at 0:03
  • \$\begingroup\$ No, this answers part of your question, using resistors for comparison. Not all comparisons in all texts on the world are meant to imply questions. There's plenty LEDs, resistors and capacitors in 0201 and 01005 packages as well as with bottom pads if they need to be larger, like the diodes, to properly function. \$\endgroup\$
    – Asmyldof
    Commented Jun 24, 2016 at 5:59
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It's not quite the same as 0603, but I often see MELF packages for SMD diodes:

enter image description here

These are pretty easy to hand-solder. The main downside is that the cylindrical packages have a tendency to roll away if you're not careful about handling them!

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    \$\begingroup\$ MELF stands for Most End up Laying on the Floor. \$\endgroup\$
    – Nick Alexeev
    Commented Jun 24, 2016 at 6:22
  • \$\begingroup\$ First lol I've ever had on stack exchange... :) \$\endgroup\$
    – bigjosh
    Commented Jun 24, 2016 at 17:15
  • \$\begingroup\$ @NickAlexeev It's not wrong! :( \$\endgroup\$
    – user39382
    Commented Jun 24, 2016 at 17:26
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In answer to why there aren't any "easy to solder" diodes, as others have shown there are some.

However the important thing to remember is that the "hobby" market is tiny compared to the industrial market, and for the industrial market, they use Pick and Place machines - you won't see many if any mass produced products that are hand soldered.

The machines have no problems with the existing packages, so why would large companies want to spend money on packaging in additional packages just to cater to a very small market.

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    \$\begingroup\$ Again, this seems to ask why normal 0603 do exist for other passives, rather than answer why they do not exist specifically for diodes. And, for the record, we've had so many hassles with reflowing the SC-79 packages. Even with a very high end domestic assembly house, it took several tweeks of the footprints to get consistently good joints- whereas 0603 parts never have problems with the standard footprints. \$\endgroup\$
    – bigjosh
    Commented Jun 24, 2016 at 1:34
  • \$\begingroup\$ BTW, this is not just relevant for hobbyists - we had a problem with a first tier USA assembly house getting low yields reflowing these diodes with the recommended pad and paste outlines. Specifically we saw solder bridging under the diode, which was very hard to inspect in circuit. It took several tweaks to get consistent results. \$\endgroup\$
    – bigjosh
    Commented Jun 10, 2017 at 18:10
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I use a simple trick to overcome any soldering issues. Increase your component's recommended land pattern by 0.5mm or so and that should ensure that you get enough space to place the component exactly where it should be. It also makes soldering the component fairly easy.

If you are unable to find the "easy to solder" parts, this trick can make sure that you are not stuck in a situation like this again.

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CDSU4148 is about as close as you will find in a 0603 package. This is functionally equivalent to a standard 1N4148 diode.

CDSU4148 on Digikey

The downside is that they are relatively expensive compared to similar diodes. FWIW - I'm in the process of changing one design from CDSU4148 to BAW56 in the SOT23-3 package BAW56 on Digikey

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I'm assuming its simply because of the different voltage and wattage capacities of the diodes. At 70V and 50mA, compared to a 0603 led at 3.3V and 20mA, the diodes have more heat to dissipate that the smaller gull wing type package can't handle.

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  • \$\begingroup\$ My General Purpose rectifiers don't leak 50mA in their blocking voltage direction at least until way past the Vbr. If yours do, they may be broken. Usually in the direction they conduct 50mA in normal use mine always fall in the 0.2V to 0.9V forward voltage region. \$\endgroup\$
    – Asmyldof
    Commented Jun 27, 2016 at 8:25

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