12
\$\begingroup\$

Why are SMD resistors marked with their value, but SMD ceramic (and similar) capacitors are not? Most SMD resistors, even the very small 0402 and 0603 ones, have their values written on them. Most SMD ceramic caps are not, I haven't to date seen a single one. The only possible reason I can think of is that resistors are far more likely to fail than capacitors as they natively dissipate heat. Supporting this theory is the fact that tantalum and aluminium electrolytic capacitors generally have a value written on them, because they are less reliable than ceramics.

Out of curiosity.

\$\endgroup\$
  • 1
    \$\begingroup\$ I've never seen a value on an 0402 resistor. \$\endgroup\$ – markrages Mar 18 '11 at 2:20
  • \$\begingroup\$ @markrages On some older 0402's, I have. Perhaps they have stopped doing it. I use 0603 in most of my designs. \$\endgroup\$ – Thomas O Mar 18 '11 at 8:02
11
\$\begingroup\$

The reason is that 'default' surface material used in resistors is suitable for printing, while on caps(ceramic dielectric) it's not. Extra coating would increase price & reduce cap quality, that's why they don't do it usually. When caps are big enough & plastic, they usually have markings.

\$\endgroup\$
  • 5
    \$\begingroup\$ Also, SMT resistors have a top and a bottom (e.g. resistive film is on only one side), while caps do not (top and bottom are interchangeable) \$\endgroup\$ – Connor Wolf Mar 18 '11 at 2:26
  • \$\begingroup\$ I've seen an example of ceramic SMD caps with printing - 0805 size or so. As I recall it wasn't readily decodable. \$\endgroup\$ – John Lopez Mar 18 '11 at 2:51
  • 2
    \$\begingroup\$ +1 can you provide a link to the reference(s) you found? \$\endgroup\$ – kenny Mar 18 '11 at 15:05
  • 2
    \$\begingroup\$ So why are tantalums frequently printed with useless nonsense ? \$\endgroup\$ – Rocketmagnet Mar 19 '11 at 11:49
0
\$\begingroup\$

I think it's simply a case that the material is harder to mark economically. Also there are typically far fewer different value caps than resistors, so the mark being there for inspection purposes is less necessary.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.