Disadvantages of Smaller SMD Caps and Resistors - Page 1
Forum section: electronics / beginners

author: jram112
author_rank: Contributor
timestamp: December 20, 2013, 09:01:46 pm
content: Are there any disadvantages of using smaller SMD caps and resistors verses larger SMD components? For example, any disadvantages using 0402 vs 0603 caps or resistors?I know they are smaller and potentially more difficult work with. I'm interested in knowing if there are any inherent material, electrical, or other disadvantages to using smaller components.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 20, 2013, 09:04:46 pm
content: Capacitors, yes at higher values (1u+). The voltage dependance tends to be worse, at higher capacitance-to-volume density, also cost rises significantly above a certain value, which is lower at smaller sizes

author: Simon
author_rank: Unknown
timestamp: December 20, 2013, 09:06:45 pm
content: Not that I'm an expert but capacitors are quite physical in their nature so smaller sizes will mean lower max capacitance and voltage combinations. Resistors will have due to physical limitations lower max power than larger counterparts. and I guess that you can argue that for resistors the max voltage may be less due to the closer spacing of the terminals but like I say I'm just hypothesizing.

author: KJDS
author_rank: Super Contributor
timestamp: December 20, 2013, 09:39:06 pm
content: I can't solder 0201 if I've had a few beers the night before.

author: mtdoc
author_rank: Super Contributor
timestamp: December 20, 2013, 09:44:49 pm
content: Quote from: KJDS on December 20, 2013, 09:39:06 pmThat's easy to fix. Just drink a few beers and practice !State Dependent Learning- then you won't be able to solder sober....

author: tld
author_rank: Regular Contributor
timestamp: December 20, 2013, 09:45:23 pm
content: Quote from: jram112 on December 20, 2013, 09:01:46 pmFor resistors, not that I know of (assuming you stay within spec)For capacitors, short version: you'll find different effective capacitances under DC bias as you reduce the size.Longer version:http://www.edn.com/design/analog/4402049/2/Temperature-and-voltage-variation-of-ceramic-capacitors--or-why-your-4-7--F-capacitor-becomes-a-0-33--F-capacitor(highly suggested reading on this topic)tld

author: matkar
author_rank: Regular Contributor
timestamp: December 20, 2013, 09:47:14 pm
content: Don't forget resistor's power rating.Quote from: Simon on December 20, 2013, 09:06:45 pmThe phenomenon is much worse than you think. With smaller capacitors nominal voltage is usually smaller in comparison to bigger ones (for the same capacitance). Ceramic capacitors are known to have much lower capacitance at higher voltages than the nominal value. With low nominal voltage capacitors this issue is more profound.

author: Simon
author_rank: Unknown
timestamp: December 20, 2013, 09:49:48 pm
content: Quote from: matkar on December 20, 2013, 09:47:14 pmI was actually refering to the fact that certain value and voltage combinations will not fit into the 0805 size as capacitance and rated voltage are physically size dependant

author: jram112
author_rank: Contributor
timestamp: December 20, 2013, 10:05:20 pm
content: Simon I am aware of that larger values of caps and larger voltages aren't available in some smaller packages.Quote from: tld on December 20, 2013, 09:45:23 pmGood article. That is some disturbing information. Just one more thing to be concerned with while designing.

author: tld
author_rank: Regular Contributor
timestamp: December 21, 2013, 12:13:55 am
content: Quote from: jram112 on December 20, 2013, 10:05:20 pmYeah, but a lot more manageable once you're aware of it. Thumbs up for the good question.tld

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 21, 2013, 12:39:33 am
content: Quote from: Simon on December 20, 2013, 09:49:48 pm..or they will fit, but are very expensive, e.g. you can get 10u 10V in an 0402, at a pricehttp://www.digikey.co.uk/product-detail/en/CL05A106MP5NUNC/1276-1450-1-ND/3889536

author: gxti
author_rank: Frequent Contributor
timestamp: December 21, 2013, 01:03:43 am
content: Voltage rating on resistors depends pretty much entirely on size. If you need one to have 240VAC across it, no matter how many megaohms, 0603 won't cut the mustard.

author: hagster
author_rank: Frequent Contributor
timestamp: December 21, 2013, 06:43:47 am
content: I have a switch mode constant current LED driver that quietly hums. My assumption is it's a capacitor changing size as the voltage squeezes it. The circuit works but I guess it might have a reduced life.

author: tszaboo
author_rank: Super Contributor
timestamp: December 21, 2013, 11:47:32 am
content: Self heating will have more effect on a smaller resistor, if you have the same current across it. On the other hand, thermal EMF is smaller, because the leads are closer. Smaller resistors and capacitors potentially have higher unwanted leakage due to flux residue. If I'm designing a precision circuit, I tend to use bigger SMD components, better dielectrics, tempco, or thin film if possible, which are easier manageable in 1206 or 0805.

author: Unknown
author_rank: Unknown
timestamp: December 21, 2013, 12:05:56 pm
content: Caps in smaller packages will generally have a lower ESL due to their smaller size. So bigger is not always better.

author: SeanB
author_rank: Super Contributor
timestamp: December 21, 2013, 01:03:53 pm
content: True, but plate resistance will be higher as the films used internally will be thinner as well. Thus ESR will be higher.

author: Unknown
author_rank: Unknown
timestamp: December 21, 2013, 02:02:10 pm
content: Both can be good for preventing resonance in decoupling caps: a higher ESR dampens resonance while a lower ESL increases its frequency.