delaminated caps

Yes, water washing unsealed devices like that has to be problematic. A warm bake at 100C for 24 hours might bring the leakage down, as long as the last rinse was really clean. Otherwise, it could leave ionic contamination wicked deep into the capacitor.

You might have to hand-install these caps after them water wash.

Jon

The current plan is:

1. Use Cornell caps.

1. Pre-assembly, inspect for cracks. The Cornells come with cracks, but less than the Panasonics.

2. After assembly, inspect again, replace any cracked caps.

1. Tell the conformal coating house to NOT do the pre-coat water dunk test. They do that to check for ionic contamination.

What a pain. How can people sell this junk?

We may have to spin the board and use thru-hole caps, Wimas maybe.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

These look good. "Box encapsulation."

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Den tirsdag den 3. marts 2015 kl. 21.21.52 UTC+1 skrev John Larkin:

until you read the datasheet:

Washing WIMA SMD components with plastic encapsulation - like all other components of similar construction irrespective of the make - cannot be regarded as herme - tically sealed. Due to today's common washing substances, e. g. on aqueous basis instead of the formerly used halo- genated hydrocarbons, with enhanced washing efficiency it became obvious that assembled SMD capacitors may show an impermissibly high deviation of the electri - cal parameters after a corresponding washing process. Hence it is recommended to refrain from applying industrial washing processes for WIMA SMD capacitors in order to avoid possible damages.

-Lasse

Looks more like a machine scraped them from the top first. I'd send the photo and maybe some of them caps to Panasonic.

DA as in dead on arrival? What happened?

Yesterday I did some load swings on a stacked ceramic cap. Touched it afterwards to see if it gets warm ... PHSSS ... OUCH. A blister on the middlefinger is real fun when reaching into the brake handle of a mountain bike. Which is what I use to get to one client and to our software engineer.

Probably a robot translation from Japanese :-)

--
Regards, Joerg 

http://www.analogconsultants.com/

Have you tried NP0 types? They are available in quite high capacitances now. Much less DA than X7R say.

--

John Devereux

Dielectric absorption. Our automated calibration was taking hours, waiting for the caps to settle. The film caps are a lot better in that respect.

I think we'll spin the board and go to molded-case thru-hole parts.

Sounds inconvenient, letting customers get that close.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Yup. I don't build anything like as many boards as you folks, but when I really need a film cap, I always use TH parts. As a bonus, they're usually much easier to clean under, so the 1/f noise is less.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

*It is not warrantable that you can mount the capacitor without trouble under all the mounting condition when ?Recommender for Land dimensions? is adopted

I think this is just a "we aren't responsible for your process" disclaimer. I doubt it has anything to do with your problems.

--

Rick

Few RTFP when the FP is 6 point.

True. Then there may also be the issue of microphonics. I remember sitting on the freeway next to your building and despite all vehicles being at a standstill there were constant vibrations and hammering coming from below.

Good plan. Occasionally SMT just doesn't cut it.

It was a bare board and ... ... my design. Unfortunately there often isn't much if any information in datasheets about dielectric losses and other losses. So I will have to move more of the filtering job to ferrites. That's this morning's job, after walking the dogs.

--
Regards, Joerg 

http://www.analogconsultants.com/

Yup, looking only at the photos, these look just like the open, unsealed ones. I sure can't see any "BOX" there at all. Maybe they try to smear some goop on the cut sides of the film, but they sure don't have a true sealed package.

Jon

Yup, I just moved our servo amps to using big NPO caps in the output filter, and am quite impressed. 160 V P-P nearly-square waves at 50 KHz, and they stay cool. 10nF 250 V caps.

Jon

The totally unpackaged caps are sold for special applications. I've only seen them in a couple places, either where huge capacitances were needed in insanely small places or where the packaging couldn't be trusted for some reason. I am pretty sure they were always hand installed after everything else.

I don't think you'd have this problem if you used epoxy-dipped parts with leads (through-hole). I think there are also epoxy-dipped film caps made for surface mount, but they are probably 5X the size due to the way they attach the SMT terminals.

I've always avoided the totally unpackaged parts, as I can't see how having the ends of the film open to the air could possibly be reliable.

Jon

We'll get some and try them. The notes that I've seen show X7R at maybe 2% DA, C0G/NP0 at 0.6%, and the PPS films at something like

0.05%. So the films are still likely to be a lot better.

This is a lowpass filter ahead of an ADC. The customer insists on a 16 Hz lowpass, and the DA of ceramic caps makes our settling times really bad.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

I've seem them fan out like a deck of cards if you try to hand solder/desolder them with a tweezer soldering iron. Nasty stuff. I'd rather use the brown epoxy dipped ones, but didn't Panasonic discontinue them?

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward" 
speff@interlog.com             Info for manufacturers: http://www.trexon.com 
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

I bought 20 of those crappy Panasonic caps too. Acetone, isopropanol, ethanol, paint thinner, and PCB flux remover will each cause them to soften, bloat, and burst open. Tried water soluble flux and they were fine until something touched them on a hot PCB. They're soft and squishy when hot. Tried again with some PCB conformal coating for protection...conformal coating solvent destroyed them.

I should have read this more carefully:

Features

- Small in size (minimum size 1.6 mm x 0.8 mm)

- 85 C, 85 %RH, W.V. x 1.0 for 500 hours

- For reflow soldering

- RoHS directive compliant

Yeah, it says 500 hours when operating as recommended.

--
I will not see posts from astraweb, theremailer, dizum, or google 
because they host Usenet flooders.

This 500hr rated voltage is a text line present on recent Panasonic film cap data sheets, including high voltage, high frequency pulse types with epoxy coatings (ECWF-A, ECWF-L).

It does not appear on data sheets where an overstress test rating is present. Typical test might be 150%/60sec. (Eg; ECQ-all, ECWF-B, ECWF-S, ECWF-U).

For SMD film, no overstress ratings are included in the spec.

This differentiation (A, L, B, U etc) occurs in the 9th character of the bulk loose piece part number (not on T&R part number) and has price and delivery implications.

RL

Yikes, we do need to coat these boards. I'll have them do one board before maybe wrecking the entire lot.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com