Choosing Package Sizes for Surface Mount Passives

[GM_Schwartz]

Hello,

I'm just getting into surface mount PCB design. I've only done one board for a class project, and the components supplied were all through hole. So before I get started on my first surface mount design, I'd like to understand the basics on this subject.

Q: How can I choose the correct package size for surface mount passive components? In other words, what factors drive the decision to use an 0603 SMD resistor/capacitor and opposed to using a 1608 package?

If anyone can provide information on this subject, I would greatly appreciate it.

Thank you in advance =)

[asmi]

I always use 0402 parts unless there is a reason to use anything else, because they are the cheapest. Factors that would case to use other package includes: need of voltage and capacitance ratings which are not available in 0402, power dissipation for resistors exceeds what 0402 can handle.

[MarkR42]

Basically, whatever parts you can get, and will fit in your project.

If it's a very tiny board and every mm of space is vital, then use smaller ones.

If you need to hand-solder, I find 0805 pretty easy, I know lots of people hand-solder 0603. I think hand-soldering 0402 or smaller is insane.

I've found that a lot more capacitors are available in 1206 size, if you want very small ones they will be low value or low voltage, watch out for very low maximum voltages on the tiny parts.

If space is not at a premium, nice big ones are handy. I now prefer a big SMD over a pin-through-hole, because it gives a lot more freedom with the board design (does not occupy other layers).

[NivagSwerdna]

For hand assembly 0603 is a good.  0603s seem to be much cheaper than 0805s... and then use bigger sizes where required due to power etc.

Maybe I will try 0402 next given Blueskull's recommendation.

[nctnico]

For hand assembly I wouldn't go below 0603. With smaller parts it becomes hard to spot bad solder joints. If space is not an issue I'd recommend to use 0805 or 1206 parts. One of the problem with smaller parts is that the area you can heat with the soldering iron also becomes smaller making soldering more difficult. 0603 already gives met problems with pads which are connected to a copper pour (even though there are thermal reliefs). On a multi-layer board this problem gets even bigger because the board absorbs more heat.

[schmitt trigger]

Like the poster above mentions, it fully depends whether this will be hand or machine assembled.

I am going to assume that they will be hand assembled. For that I have employed 0603s. Good compromise between board density and ease of assembly, more so if you are a beginner.

But in the last couple of years, my eyesight is becoming weaker and my pulse shakier , and thus my newer projects exclusively use 0805s. 

[asmi]

For hand assembly I wouldn't go below 0603. With smaller parts it becomes hard to spot bad solder joints. If space is not an issue I'd recommend to use 0805 or 1206 parts. One of the problem with smaller parts is that the area you can heat with the soldering iron also becomes smaller making soldering more difficult. 0603 already gives met problems with pads which are connected to a copper pour (even though there are thermal reliefs). On a multi-layer board this problem gets even bigger because the board absorbs more heat.

Sounds like the problem is the soldering iron/station. I have no problems soldering even 0201's to power/ground planes using ADS200 (under microscope of course). But I try to avoid 0201's because they are more expensive than 0402, and only use the former if I have to. Typically that's decoupling caps under BGAs where there is simply not enough space for 0402, also 0201 have smaller ESL which helps to reduce parasitic inductance. And when I use 0201's, I usually reflow them rather than solder them manually.

[SiliconWizard]

For a complete beginner, I would not go below 0805, and 1.27mm pitch ICs, that would just end up in frustration. That's what I did anyway.

Once you're familiar with the process, you can try 0603, then 0402, and finer pitches.
The key is to use small diameter solder wire. 0.7mm is too much for most SMD tasks except large tabs, I mainly use 0.2mm. Another frequent mistake as a beginner is to use very small tips. No need for them for most tasks and they just make your life much tougher. Not much more to it than that and a steady hand.

[Warhawk]

Hello,

I'm just getting into surface mount PCB design. I've only done one board for a class project, and the components supplied were all through hole. So before I get started on my first surface mount design, I'd like to understand the basics on this subject.

Q: How can I choose the correct package size for surface mount passive components? In other words, what factors drive the decision to use an 0603 SMD resistor/capacitor and opposed to using a 1608 package?

If anyone can provide information on this subject, I would greatly appreciate it.

Thank you in advance =)

You did not mention what you want to do. Are you talking hobby or professional applications? I assume hobby applications. If you want to do just 2-layer PCBs, then even 1206s may be the right fit. You can fit up to two tracks underneath and this may save you a lot of hassle. Also, you eyesight matters. I started with 1206s, went to 0805s, then to 0603s and now, I am considering stepping up to 0805s. Honestly, I don't see much space savings when I compare 0603s and 0805s. However, my soldering for 0805s and 1206s looks significantly better than for 0603s and I am not a newbie with a soldering station.

tl;dr; 

- well soldered 1206s are better than poor soldered 0603s
- size does not matter  as long as you don't exceed the power rating (don't do more than 50% of the nominal rating)
- MLCC capacitors sizes vary with capacitance and voltage rating. Don't make them too small. Extremes cost extreme prices. Always check for a mainstream X7R MLCC cap for the reference. Ignore Y5R etc. That's rubbish.
- go 0805s for your first project and you will see how it works for you. Don't be afraid of using even 1206s. There is nothing wrong with them unless you do high volume products.
- Use SOIC packages for opamps and logic circuits. Don't push the technology to the limit.
   
Good luck and share your results !

[KL27x]

The main reason to avoid going too small, IMO, is because of the hand placing. The problem is not soldering the tiny parts, it's getting the part on the board in the first place. The smaller the part, the smaller the needle you need to pick it up. The easier it is for parts to stick in the tape (if you're picking them up from the tape), or to pick up a clump of 3-4 of them if out of a dish, and the tiny parts are more likely to cling to the pickup needle if it isn't meticulously clean, instead of immediately falling off. It is also harder to see if the pads are pasted/fluxed and blank or if you already put that spec of dirt on top until you get the board under magnification.

IME, the pickup tools and the tweezers are more important than the soldering iron. I have never had any trouble soldering tiny parts, even when I use a $10.00 iron to put 0201 resistors on protoboard.

For prototyping, another reason is that 0402 and smaller resistors almost never have markings on them. 0805 and larger are always marked, IME. 0603 are 50:50.

For these reasons, I tend to bottom out at 0603 for resistors, but I am ok with using 0402 caps if the specs and price are good. The caps are taller/heavier and are thusly not as annoying to handle; they still act like they have some mass rather than being a tiny flake of styrofoam that clings to the tiniest bit of magnetism or nanogram of finger oil. Plus they won't be marked with a value, anyway.

[free_electron]

A word of advice : 0805 and larger are on their way out. For resistors AND capacitors.
It is more cost effective for manufacturers to build the smaller parts  and the demand for those is larger as well.

[Warhawk]

A word of advice : 0805 and larger are on their way out. For resistors AND capacitors.
It is more cost effective for manufacturers to build the smaller parts  and the demand for those is larger as well.

I doubt this. The fact that the industry is moving towards smaller components does not mean that 1206s or 0805s will disappear.

[KL27x]

^count me, as a doubter. Esp for resistors; the larger the resistor the greater the wattage it can dissipate. Heck, I have resistors in 2412 I have used for driving LEds from mains.

And 0805 can sometimes be cheaper for the quantities you might want, due to the available sizes of full reels. 

 

[tautech]

A word of advice : 0805 and larger are on their way out. For resistors AND capacitors.
It is more cost effective for manufacturers to build the smaller parts  and the demand for those is larger as well.

Thanks for the heads up, I for one don't doubt your experience and knowledge in leading edge electronics.

Still that's somewhat a shame as 0805 is the easiest to get to grips with for those diving into SMD as you don't need anything special in the way of gear to work with them. For the younger of us even magnification is not required. Sadly not so for me. 
With the experience gained using 0805 I'd now have little concern in going to 0603 but smaller would be a PITA.

[IconicPCB]

dont ignore power dissipation requirements...reason to go large.

[Neilm]

A word of advice : 0805 and larger are on their way out. For resistors AND capacitors.
It is more cost effective for manufacturers to build the smaller parts  and the demand for those is larger as well.

The company I work at has seen this as well - manufacturers are concentrating on the smaller sizes. Common values have skyrocketed in the last couple of years with order times of over 1 year. Yes the larger sizes are needed for power dissipation or voltage ratings, but if a manufacturer has a choice between 2 sizes and one is in higher demand and make more them money they are going to make the one that will make them more money - even if the other components are better for hand placement (how many of those are there? 10k per year tops).

[Siwastaja]

IMHO, 0402 tends to be the best general-purpose compromise between:
* good enough integration/miniatyrization level
* availability of parts
* cost
* manufacturability in any low cost assembly house, and
* ability to hand solder them.

If you value hand solderability a lot and expect rework, use 0603 instead, it's easier to work with, generally; but depends on person. For me, 0402 is no problem whatsoever either, just a tiny bit more tedious and slower.

OTOH, for example, when you decouple power pins of a 0.5mm pitch device, 0603 ceramic caps are huge and require stupid routing techniques, often blocking other signals; 0402 is way easier, and you won't rework your power decoupling caps.

0805 and bigger: only use when absolutely needed. Typically for power dissipation or large capacitance.

[cowasaki]

I bought some brilliant SMD storage containers then I bought 1206 as I hadn't used any other size.  The actual parts are ridiculously cheap so I then bought 0805 and 0603.  I just got full kits from Chinese sellers for under £10 for 25 each of 140+ values.  Basically, any of these sizes are reasonable easy to solder.  My new Amscope makes it somewhat easier to see them now as well but I was managing with an 8x illuminated desk magnifier.  I'm using a Duratool combined soldering and desoldering station.  It's quite passable but every time I have enough to replace it I end up buying something else like the Amscope.  I have three irons and two desoldering irons for it and it still works.  That's what I use and it's fine. Although I'm going to get a JBC soon (unless I spend the money on a bench PSU or some other alternative!)