hmm?
resistors have numbers
capacitors are blank tan colored.

 

They can be purchased with or without labels. It costs more and helps people who would reverse-engineer a circuit, so many forgoe the markings.

 

They can be purchased with or without labels. It costs more and helps people who would reverse-engineer a circuit, so many forgoe the markings.

But it would seem that same argument would go for resistors and yet I've never seen unlabeled resistors (I don't recall if the 0402 and 0201 resistors I've worked with were labeled or not), though they may exist. Seems like not knowing the resistor values in a circuit would be a much greater hindrance to reverse engineering a circuit than not know the capacitor values. In either case, anyone that is serious about reverse engineering a circuit isn't going to have any qualms about dismantling a circuit and measuring the individual components.

While I always found unmarked caps an annoyance, in most circuits I was only using a few different values and they were usually far enough apart that the caps were physically different thicknesses, so keeping them straight wasn't much of an issue. That definitely wasn't the case for resistors and had they not been marked the pace of my work would have been drastically slowed. But, again, I doubt that was a major consideration in the decision since they are intended for automatic pick-and-place machines and they really don't care about the inconveniences imposed on one-off board makers.

 

Apparently, some ceramics are marked or at least can be: http://www.niccomp.com/catalog/storage.pdf

Here is another discussion of the subject: http://electronics.stackexchange.com/questions/115095/surface-mount-capacitor-marking

Since we know that small tantalum caps are marked, it seems that the suggestion regarding difficulty in printing on the ceramic package may have some merit.

John

 

I guess ceramic caps won't be labeled until somebody invents a paint that will stick to them.

 

Why???

<Begin rant>
Because capacitor manufacturers have a long history of making the values hard to read. Why should they change now?
<End rant>

 

I guess ceramic caps won't be labeled until somebody invents a paint that will stick to them.

Paint won't stick to them but plain old ink will. And yeah, I have seen ceramic SMD caps that were labeled using a code along with the ceramic coating being dyed in pretty pastel colors.

 

SMD caps are produced as individual units. SMD resistors are produced on large sheets then segmented into individual items. It is possible the resistor marking is done in the panelized version thus the cost is insignificant <citation needed>.

SMD capacitors actually predate SMD techniques by several decades where they were used in hybrid microcircuit assembly. Such hybrids have very few if any markings on the components. They heavily rely on the assembly drawing to put things where they belong.

One very good engineer I once (twice actually) worked with had a large hybrid circuit requiring 20x of each of two different value caps. He intentionally chose caps by voltage rating to get two different sizes to aid in their correct placement.