Why don't they mark SMD caps?

What labour ?

geoff

Reply to
geoff
Loading thread data ...

SMD resistors get a ceramic glaze coating over the applied resistance medium. It gets fired on. The lettering is usually fired glaze as well. The resistance medium is hygroscopic, so they have to seal it up.

multilayer chip caps CANNOT be fired in an oven that way. They barely make it through the reflow process.

Reply to
Archimedes' Lever

Note the requisite that was declared. They are 0805 or larger.

The absolute cheapest variety will not have them. The higher end varieties likely will.

The customer pays for the cap substrate medium and its termination method. The markings never were charged for from my recall.

Reply to
Archimedes' Lever

What I hate about these components, I am looking at 3 0805 bits, one is a resistor, the second is a cap, and I have no idea what the third is but they are the same colour.

Reply to
Wayne.

Learn to read, ditz! Nobody was talking about resistors. Christ! That is even obvious from the title!

Reply to
Archimedes' Lever

Yep, that's fine, you don't expect them on smaller ones.

Like I said, can you provide links?

Dave.

--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
 Click to see the full signature
Reply to
David L. Jones

Because resistors are fired glazed parts to seal the resistance medium from moisture, and that can have legible letters included. If chip caps had an outer glaze or epoxy slab on them, lettering could easily be added. The industry has found better performance from uncoated MCCs, and fire glazing is out of the question as the layer terminations are thermally sensitive.

The chip cap markings, even on the larger form factor parts, was a very fuzzy, out of focus character set, beneath the actual first surface of the mlcc. Maybe laser etched or it is a very very thin ink. Some were surface marked, but most were submerged. On a smaller form factor, that becomes very hard to see, and adds labor to inspect via the marking, and it does become harder to manufacture as well, causing more fab failures before they even get going.

Visual comparison with the reel is the most common and preferred method for already installed parts. Visual comparison and testing for loose parts. Some can be ID'd by their 'color', which *can* indicate substrate choice,which should be easy to note on the reel info label. When certain caps are a buck each (microwave SMD chip caps), and others are fractions of a penny (El Cheapo Browno), one wants to be sure that one places the right part in the right locations.

Reply to
Archimedes' Lever

Umm, yes it's about resistors too, it was mentioned in my very first post. My original question is why don't they mark SMD capacitors, when it's very common to mark the same size SMD resistors. So Sergey's remark is perfectly valid. It's common to mark cheap resistors, but it's not common to mark more expensive capacitors of the same size - why? It's clearly not about cost, as Rich mentioned. I'm assuming the reason is technical/process related, and not historical etc, but I'm not sure, so that's why I asked.

Dave.

--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
 Click to see the full signature
Reply to
David L. Jones

Why do resistors of the same size still commonly have the markings then? It's not about the size, we are talking 1206/0805 and other large sizes here. Markings on these size caps are not common (some would say rare), and it's

*always* been that way. The question is why?...

Dave.

--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
 Click to see the full signature
Reply to
David L. Jones

Now, in the modern facility, post assembly inspection doesn't really even happen any more as it relates to part values. Most post reflow inspection is for locating any tombstoned or pad shifted parts.

BGA requires X-ray to inspect.

There was a time, however, when a post process inspector would actually examine the discreet parts on an assembly, and verify the value of parts. This was particularly true of a first article assembly, prior to a production run.

Now that form factors are so small, actual part value verification on assemblies is rare. It is also more difficult. Even with the magnification aids.

And the likelihood that a test or repair technician would know how to read a chip cap with anything other than a meter is very, very close to nil.

Reply to
Archimedes' Lever

on=20

and=20

markings.

on=20

altered=20

=20

Simple, because they have gotten away with it for 30 years.

Reply to
JosephKK

=20

temperature,=20

=20

roller=20

print to=20

Come to think of it, wave solder is more of a through hole process. The modern process is reflow. Wave solder does not pay well with SMD parts on both sides, reflow does.

Reply to
JosephKK

I found AVX data sheets that show them (markings), butI would want to see marking actually mentioned in the data before I post what I find.

Reply to
Archimedes' Lever

It maybe has "always been that way" with el cheapo brands, but I used to do pre-reflow inspection (post pick and place), and have loaded the cassettes into the picker placer, and have loaded the reels into the cassettes and have programmed the PCB into it... yada yada yada...

I have seen a lot of caps that were marked, so you are either using cheap parts and always have, or your "always has" only amounts to a year or two, since they now seldom do it.

Reply to
Archimedes' Lever

I like obsolete marking systems.

formatting link

Reply to
Archimedes' Lever

Six at most. When I inspected assemblies, many years ago (14?), they were there, and when I designed assemblies more recently, I began to see them disappearing.

Form factor is the reason, and lack of true need, IMO.

The first thing I do to deck out my proto bench is make out about 300 pcs each of every cap and resistor (and most all tape and reel parts other than big chips)we have in stock in bulk. Little 10 or 20 pc strips fit real nice in a parts cabinet drawer. Smaller samples of those we have less counts of, of course. Marking the P/N and or value on the back and or front with a sharpie IDs each strip just fine.

That way, future ID through visual comparison is also capable, as the parts are in my kit cabinet to compare with.

Reply to
Archimedes' Lever

Originally, SMD parts were used along with thru hole. The "solder side", as it was called, had thermal cure glue at all the SMD locations, and the SMD parts get placed with no solder paste at all, and then the curing oven bakes them in place. Then the boards went to a push line or auto-inserter and the thru hole parts get added, being careful with the solder side attached-but-not-yet-soldered parts. During wave solder, the PCB gets passed over a flux bubbler. Next thing you know, the thru hole and the bottom side SMD parts are soldered.

Reply to
Archimedes' Lever

From "Ceramic Commercial-Off-The-Shelf Surface Mount Capacitors (COTS)" from Kemet:

"Marking These chips are supplied unmarked. If required, they can be laser-marked as an extra cost option. Details on the marking format are included in KEMET Surface Mount Catalog F3102."

Reply to
E

OK, I'll take the oops on that one.

Thanks, Rich

Reply to
Rich Grise

Can you poin us at not-so-cheap marked SMD capacitors so I would always use those in my projects? I don't care if they twice the price of those unmarked cheap ones...

--
******************************************************************
*  KSI@home    KOI8 Net  < >  The impossible we do immediately.  *
 Click to see the full signature
Reply to
Sergey Kubushin

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.