SMD electros ?

[Phil Allison]

Hi all,

I have just come across a PCB where all 17 of the 4.7 uF, SMD ,
*aluminium* electros are more or less open circuit. All give no reading on a
Bob Parker ESR meter and when removed and tested show low to no capacitance.
All the similar 2.2 uF caps test fine - a couple of 1 uF ones have highish
ESR. The PCB is about 4 years old and does not run hot.

How common is this sort of problem and what might have produced it ?

Could the caps simply have been overheated and damaged when being mounted?

How do they solder such caps to the PCB in the factory without overheating
them ?





.......... Phil

 

[The Real Andy]

On Thu, 5 Aug 2004 18:04:42 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

Hi all,

I have just come across a PCB where all 17 of the 4.7 uF, SMD ,
*aluminium* electros are more or less open circuit. All give no reading on a
Bob Parker ESR meter and when removed and tested show low to no capacitance.
All the similar 2.2 uF caps test fine - a couple of 1 uF ones have highish
ESR. The PCB is about 4 years old and does not run hot.

How common is this sort of problem and what might have produced it ?

Could the caps simply have been overheated and damaged when being mounted?

How do they solder such caps to the PCB in the factory without overheating
them ?

......... Phil

Is this some kind of test? At a guess, i would be thinking along the
lines of a faulty batch. I doubt they would have been overheated
during manufacture, as the problem would be across the whole board.

Soldering in mass manufactured goods is usually done via IR reflow.
The heat can be varied across board. If you take a look at the cap
manufacturers specs, they will provide data on reflow and solder
profiles that provide safe limits for manufacture.

 

[Phil Allison]

"The Real Andy"
"Phil Allison"

I have just come across a PCB where all 17 of the 4.7 uF, SMD ,
*aluminium* electros are more or less open circuit. All give no reading
on a
Bob Parker ESR meter and when removed and tested show low to no
capacitance.
All the similar 2.2 uF caps test fine - a couple of 1 uF ones have
highish
ESR. The PCB is about 4 years old and does not run hot.

How common is this sort of problem and what might have produced it ?

Could the caps simply have been overheated and damaged when being
mounted?

How do they solder such caps to the PCB in the factory without
overheating
them ?



Is this some kind of test?

** Nope.

Soldering in mass manufactured goods is usually done via IR reflow.

** Thanks for that info - Google has filled in the details.

The heat can be varied across board. If you take a look at the cap
manufacturers specs,

** Ummm - how do I tell who the maker is ????????


they will provide data on reflow and solder

profiles that provide safe limits for manufacture.

** The Nichicon site PDF data says max 250 C PCB surface temp for 30
second - but these dudes may not be Nichicons.

Sounds like a cruel way to treat a tiny cap with juice inside that boils at
circa 115 C.




............. Phil

 

[Ross Herbert]

On Thu, 5 Aug 2004 18:04:42 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

|Hi all,
|
| I have just come across a PCB where all 17 of the 4.7 uF, SMD ,
|*aluminium* electros are more or less open circuit. All give no reading on a
|Bob Parker ESR meter and when removed and tested show low to no capacitance.
|All the similar 2.2 uF caps test fine - a couple of 1 uF ones have highish
|ESR. The PCB is about 4 years old and does not run hot.
|
| How common is this sort of problem and what might have produced it ?
|
| Could the caps simply have been overheated and damaged when being mounted?
|
| How do they solder such caps to the PCB in the factory without overheating
|them ?
|
|
|
Phil,

I haven't come across this problem myself... so far.

One possible cause I can think of why only some values are affected on
your pcb's is that when the board was produced some components may
have required changing (or were inadvertently left off) thus requiring
a second reflow, or the first reflow procedure was not effective for
some reason. The caps not affected may only have experienced one
reflow cycle which is the preferred maximum for SMD electros.

Nichicon's design guide says this;

Reflow soldering (SMD only)
Soldering condition must be confirmed to be within Nichicon
specification.
Pre-heating : Less than 150°C, 90 seconds max.
Max. temperature at capacitor top during reflow : 230°C
The duration for over 200°C temperature at capacitor
top: 20 seconds max.

The duration from the pre-heat temperature to peak temperature of
reflow varies due to changes of the peak temperature. Refer to page
17 for details.

When an infrared heater is used, please pay attention to the extent of
heating since the absorption rate of infrared, will vary due to
difference in the color of the capacitor body, material of the sleeve
and capacitor size.

The number of reflow times for SMD aluminum electrolytic capacitors
shall be one time. If this type of capacitor has to be inevitably
subjected to the reflow twice, enough cooling time between the first
and second reflow (at least more than 30 minutes) shall be taken to
avoid consecutive reflow. Please contact our sales office if you have
questions.

 

[gcd]

Hi all,
another possibility - could simply be a bad design, depending on the rails
they are on and the margins allowed for in the design etc.

and another - if the board also has leaded components and the electros are
on the solder side for the leaded components then the board goes through
wave soldering with pallets installed to protect the surface mount
components from the heat of the wave. if this wasn't done correctly or were
in the wave too long I expect that may have exposed the caps excessively.

Cheers
Greg


"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2ne80tFvdp6rU1@uni-berlin.de...

Hi all,

I have just come across a PCB where all 17 of the 4.7 uF, SMD ,
*aluminium* electros are more or less open circuit. All give no reading on
a
Bob Parker ESR meter and when removed and tested show low to no
capacitance.
All the similar 2.2 uF caps test fine - a couple of 1 uF ones have
highish
ESR. The PCB is about 4 years old and does not run hot.

How common is this sort of problem and what might have produced it ?

Could the caps simply have been overheated and damaged when being
mounted?

How do they solder such caps to the PCB in the factory without
overheating
them ?





......... Phil

 

[Phil Allison]

"gcd"

another possibility - could simply be a bad design, depending on the rails
they are on and the margins allowed for in the design etc.

** They appear to all be 50 volt rated caps and are used for audio signal
coupling.

and another - if the board also has leaded components and the electros are
on the solder side for the leaded components ......

** There are normal leaded components and hardware items ( pots, jacks and
heatsinks) on the same PCB which must have been loaded and flow soldered
from beneath in a later operation. All components are on the same side of
the board.



.............. Phil

 

[John Crighton]

On Thu, 05 Aug 2004 20:32:29 +1000, The Real Andy
<.pearson@wayit_dot_com_dot_au_remove_the_obvious_to_reply> wrote:

On Thu, 5 Aug 2004 18:04:42 +1000, "Phil Allison"
philallison@tpg.com.au> wrote:

Hi all,

I have just come across a PCB where all 17 of the 4.7 uF, SMD ,
*aluminium* electros are more or less open circuit. All give no reading on a
Bob Parker ESR meter and when removed and tested show low to no capacitance.
All the similar 2.2 uF caps test fine - a couple of 1 uF ones have highish
ESR. The PCB is about 4 years old and does not run hot.

How common is this sort of problem and what might have produced it ?

Could the caps simply have been overheated and damaged when being mounted?

How do they solder such caps to the PCB in the factory without overheating
them ?

......... Phil


Is this some kind of test? At a guess, i would be thinking along the
lines of a faulty batch. I doubt they would have been overheated
during manufacture, as the problem would be across the whole board.

Hello Andy, Phil and the group,

Andy when you said "I doubt they would have been overheated"
that brought back memories of working at a joint in Frenchs Forest
that made Paging Transmitters. The small surface mount components
were done by machine outside the company but the bigger components
including the larger brown coloured chip capacitors were put on the
boards by hand by travellers doing some temporary work and the
big bosses daughter and the other big bosses teenage son. 60 watt
birko soldering irons and unskilled people is bad enough. Now here is
the funny bit. The Chinese engineer would come down to the assembly
room and complain "Not enough solder! Not enough solder!"
"Use lot solder on transistor capacitor" So the big soldering irons
would go over the chip capacitors a second time. The big boss would
come in and insist that some boards be touched up with more
solder on the capacitors and RF power transistors. You guessed
it. Months later the transmitters were returned with holes in the PCB
where large chip capacitors had burnt up, other chip capacitors
just failed silently.

Soldering in mass manufactured goods is usually done via IR reflow.
The heat can be varied across board. If you take a look at the cap
manufacturers specs, they will provide data on reflow and solder
profiles that provide safe limits for manufacture.

Later on a Sunbeam electric frying pan was used to gently heat
the chip capacitors before soldering them to a warmed board.
One guy was then soldering them on. Once only! No touch ups,
and the failures reduced enormously.

I remember my work mate at the time expressing concern
about the boss's kids doing this work, with giant soldering
irons and being shouted down. I guess when one is a millionaire
factory owner, one gets to employ who one likes.
Another thing that concerned me at the time was that the additional
components were put on boards that were bowed, then screwed
down flat onto a chassis. A bit of mechanical stress chucked in
for good measure.
A bit of a laugh then and now when I think about it.

Phil, the Bob Parker ESR meter. Yes, top marks to Bob, we should
take him for a drink sometime. My newly assembled 50 dollar mark 1
model, found a bunch of dud electros in a little Marconi Bridge
TF2700, that I was looking at lately. Very handy indeed! Then
again the TF2700 was made in the mid 60s so all the electros
should be replaced to allow it to serve for another 20 years. That
should just about see me out. Cripes! That's what my mum and her
cronies at the retirement village say when they buy new shoes
or a cardigan. Now they have got me saying it.

Regards,
John Crighton
Hornsby Heights

 

[The Real Andy]

On Thu, 05 Aug 2004 14:42:14 GMT, john_c@tpg.com.au (John Crighton)
wrote:

On Thu, 05 Aug 2004 20:32:29 +1000, The Real Andy
.pearson@wayit_dot_com_dot_au_remove_the_obvious_to_reply> wrote:

On Thu, 5 Aug 2004 18:04:42 +1000, "Phil Allison"
philallison@tpg.com.au> wrote:

Hi all,

I have just come across a PCB where all 17 of the 4.7 uF, SMD ,
*aluminium* electros are more or less open circuit. All give no reading on a
Bob Parker ESR meter and when removed and tested show low to no capacitance.
All the similar 2.2 uF caps test fine - a couple of 1 uF ones have highish
ESR. The PCB is about 4 years old and does not run hot.

How common is this sort of problem and what might have produced it ?

Could the caps simply have been overheated and damaged when being mounted?

How do they solder such caps to the PCB in the factory without overheating
them ?

......... Phil


Is this some kind of test? At a guess, i would be thinking along the
lines of a faulty batch. I doubt they would have been overheated
during manufacture, as the problem would be across the whole board.

Hello Andy, Phil and the group,
Andy when you said "I doubt they would have been overheated"
that brought back memories of working at a joint in Frenchs Forest
that made Paging Transmitters. The small surface mount components
were done by machine outside the company but the bigger components
including the larger brown coloured chip capacitors were put on the
boards by hand by travellers doing some temporary work and the
big bosses daughter and the other big bosses teenage son. 60 watt
birko soldering irons and unskilled people is bad enough. Now here is
the funny bit. The Chinese engineer would come down to the assembly
room and complain "Not enough solder! Not enough solder!"
"Use lot solder on transistor capacitor" So the big soldering irons
would go over the chip capacitors a second time. The big boss would
come in and insist that some boards be touched up with more
solder on the capacitors and RF power transistors. You guessed
it. Months later the transmitters were returned with holes in the PCB
where large chip capacitors had burnt up, other chip capacitors
just failed silently.

Soldering in mass manufactured goods is usually done via IR reflow.
The heat can be varied across board. If you take a look at the cap
manufacturers specs, they will provide data on reflow and solder
profiles that provide safe limits for manufacture.

Later on a Sunbeam electric frying pan was used to gently heat
the chip capacitors before soldering them to a warmed board.
One guy was then soldering them on. Once only! No touch ups,
and the failures reduced enormously.

I remember my work mate at the time expressing concern
about the boss's kids doing this work, with giant soldering
irons and being shouted down. I guess when one is a millionaire
factory owner, one gets to employ who one likes.
Another thing that concerned me at the time was that the additional
components were put on boards that were bowed, then screwed
down flat onto a chassis. A bit of mechanical stress chucked in
for good measure.
A bit of a laugh then and now when I think about it.

Phil, the Bob Parker ESR meter. Yes, top marks to Bob, we should
take him for a drink sometime. My newly assembled 50 dollar mark 1
model, found a bunch of dud electros in a little Marconi Bridge
TF2700, that I was looking at lately. Very handy indeed! Then
again the TF2700 was made in the mid 60s so all the electros
should be replaced to allow it to serve for another 20 years. That
should just about see me out. Cripes! That's what my mum and her
cronies at the retirement village say when they buy new shoes
or a cardigan. Now they have got me saying it.

Regards,
John Crighton
Hornsby Heights

John, is that Frenchs Forest the one in QLD?

If its any where in au then I would laugh. If it was in TW (or china
these days) I would not believe you.

 

[The Real Andy]

On Thu, 5 Aug 2004 21:04:07 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

"The Real Andy"
"Phil Allison"


I have just come across a PCB where all 17 of the 4.7 uF, SMD ,
*aluminium* electros are more or less open circuit. All give no reading
on a
Bob Parker ESR meter and when removed and tested show low to no
capacitance.
All the similar 2.2 uF caps test fine - a couple of 1 uF ones have
highish
ESR. The PCB is about 4 years old and does not run hot.

How common is this sort of problem and what might have produced it ?

Could the caps simply have been overheated and damaged when being
mounted?

How do they solder such caps to the PCB in the factory without
overheating
them ?



Is this some kind of test?


** Nope.


Soldering in mass manufactured goods is usually done via IR reflow.


** Thanks for that info - Google has filled in the details.


The heat can be varied across board. If you take a look at the cap
manufacturers specs,


** Ummm - how do I tell who the maker is ????????

Thats the prob with SM passives, you're lucky if you even get a value
on the can.

they will provide data on reflow and solder
profiles that provide safe limits for manufacture.


** The Nichicon site PDF data says max 250 C PCB surface temp for 30
second - but these dudes may not be Nichicons.

Pre heat and cool down periods are also very critical. See my reply to
Ross Herbert.

Sounds like a cruel way to treat a tiny cap with juice inside that boils at
circa 115 C.

Its only thirty seconds, cahnces are that using modern IR reflow
profiles you wont even get 30second under full heat.

 

[The Real Andy]

On Thu, 05 Aug 2004 11:05:27 GMT, Ross Herbert
<rherber1SPAMEX@bigpond.net.au> wrote:

On Thu, 5 Aug 2004 18:04:42 +1000, "Phil Allison"
philallison@tpg.com.au> wrote:

snip

I haven't come across this problem myself... so far.

One possible cause I can think of why only some values are affected on
your pcb's is that when the board was produced some components may
have required changing (or were inadvertently left off) thus requiring
a second reflow, or the first reflow procedure was not effective for
some reason. The caps not affected may only have experienced one
reflow cycle which is the preferred maximum for SMD electros.

Nichicon's design guide says this;

Reflow soldering (SMD only)
Soldering condition must be confirmed to be within Nichicon
specification.
Pre-heating : Less than 150°C, 90 seconds max.
Max. temperature at capacitor top during reflow : 230°C
The duration for over 200°C temperature at capacitor
top: 20 seconds max.

The duration from the pre-heat temperature to peak temperature of
reflow varies due to changes of the peak temperature. Refer to page
17 for details.

When an infrared heater is used, please pay attention to the extent of
heating since the absorption rate of infrared, will vary due to
difference in the color of the capacitor body, material of the sleeve
and capacitor size.
snip

There has been a lot of debate about common reflow profiles to date re
adverse heating of different coloured components. A lot of
manufacturers seem to use common profiles, but a lot of mass
manufacturers are changing profiles these days. If you do a google
search on IR reflow profiles you will see the arguments.

You will also find that modern reflow machines have seperate zones to
control heating in different areas. With the advent of BGA packages
this is becoming even more important these days. A good manufacturer
will take into consideration the different style of components.

OT: It is unlikely that you will obtain this kind information from AU
manufacturers, so it is worthwile doing some research before you
decide on a contract manufacturer.

 

[Bob Parker]

john_c@tpg.com.au (John Crighton) wrote:

Phil, the Bob Parker ESR meter. Yes, top marks to Bob, we should
take him for a drink sometime. My newly assembled 50 dollar mark 1
model, found a bunch of dud electros in a little Marconi Bridge
TF2700, that I was looking at lately. Very handy indeed!

Thanks John!
And you didn't think I was reading all this, did you? I don't
mind Hahn, or some nice Hunter old or Guiness will do just fine.
Even after all this time (coming up on 9 years already?), I still
like hearing that my little meter I made for myself is helping out
other techs.

Cheers,
Bob

 

[Mark Harriss]

I have about 400 units of three different 100uF SMD's that are unused
and have leaked electrolyte all over their containers. I'm a bit wary of
using them at all now as it affects the different batches/brands.

Mark H

 

[Phil Allison]

"Mark Harriss"

I have about 400 units of three different 100uF SMD's that are
unused
and have leaked electrolyte all over their containers. I'm a bit wary of
using them at all now as it affects the different batches/brands.

Mark H

** Ah - the plot thickens.

So SMDs electros are not all they are cracked up to be.

Thanks for that info Mark.






........... Phil

 

[Bob Parker]

Hmmmmm,
I thought it was fairly common knowledge that the most unreliable
electronic components of all are SMD aluminium electrolytic caps...?
They are the major cause of camcorders failing, for example.
Someone once told me that NASA won't allow aluminium electrolytic
caps to be used in any flight control systems on their spacecraft,
which says something about what horrible components they are.

Bob


"Phil Allison" <philallison@tpg.com.au> wrote:

"Mark Harriss"


I have about 400 units of three different 100uF SMD's that are
unused
and have leaked electrolyte all over their containers. I'm a bit wary of
using them at all now as it affects the different batches/brands.

Mark H



** Ah - the plot thickens.

So SMDs electros are not all they are cracked up to be.

Thanks for that info Mark.






.......... Phil

 

[Phil Allison]

"Bob Parker"

Hmmmmm,
I thought it was fairly common knowledge that the most unreliable
electronic components of all are SMD aluminium electrolytic caps...?
They are the major cause of camcorders failing, for example.

** Not too many folk fix those.

Someone once told me that NASA won't allow aluminium electrolytic
caps to be used in any flight control systems on their spacecraft,
which says something about what horrible components they are.

** Or more likely that the extreme conditions ( very high and low temps)
make them non suitable.




........... Phil

 

[Franc Zabkar]

On Sun, 15 Aug 2004 05:47:38 +1000, Bob Parker <bobp@bluebottle.com>
put finger to keyboard and composed:

Hmmmmm,
I thought it was fairly common knowledge that the most unreliable
electronic components of all are SMD aluminium electrolytic caps...?

I thought so, too. IME no manufacturer is immune to this problem.
Fluke, Sony, Macintosh are three bad experiences that come to mind.

They are the major cause of camcorders failing, for example.

Agreed. A colleague regularly replaces fistfuls of these caps.

Someone once told me that NASA won't allow aluminium electrolytic
caps to be used in any flight control systems on their spacecraft,
which says something about what horrible components they are.

Bob

There is a mainboard review in one of the local computer mags. I can't
be sure, but several of the photographs suggest that a number of
motherboards are using these caps in their Vcore circuits. Makes me
shudder ...


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Phil Allison]

"Franc Zabkar" <
Bob Parker

Hmmmmm,
I thought it was fairly common knowledge that the most unreliable
electronic components of all are SMD aluminium electrolytic caps...?

I thought so, too. IME no manufacturer is immune to this problem.
Fluke, Sony, Macintosh are three bad experiences that come to mind.

They are the major cause of camcorders failing, for example.

Agreed. A colleague regularly replaces fistfuls of these caps.

Someone once told me that NASA won't allow aluminium electrolytic
caps to be used in any flight control systems on their spacecraft,
which says something about what horrible components they are.

Bob

There is a mainboard review in one of the local computer mags. I can't
be sure, but several of the photographs suggest that a number of
motherboards are using these caps in their Vcore circuits. Makes me
shudder ...

** Hmmmm - sounds like I better get some smaller and pointier probes for
my Bob Parker ESR meter ....

Plus carry stock of the little SMD suckers.




.............. Phil

 

[Bob Parker]

"Phil Allison" <philallison@tpg.com.au> wrote:

** Not too many folk fix those.

And very wise those folk who avoid camcorders are, too! I've still
got an old Canon one in dozens of pieces here. SMD electrolytics all
over most or all of the boards had leaked, with electrolyte seepage
under other components and tracks corroded right through. It was
beyond economically fixing. That was the first and last time I
ventured inside a camcorder.

** Or more likely that the extreme conditions ( very high and low temps)
make them non suitable.

Yeh, ordinary electrolytics, extreme conditions and the need for
extreme reliability definitely don't mix.

** Hmmmm - sounds like I better get some smaller and pointier probes for
my Bob Parker ESR meter ....

Plus carry stock of the little SMD suckers.

Grin! Thanks for the (latest) plug.


Regards,
Bob

 

[dmm]

On Sat, 14 Aug 2004 08:25:49 GMT, Mark Harriss <anotheremail@this.com> wrote:

I have about 400 units of three different 100uF SMD's that are unused
and have leaked electrolyte all over their containers. I'm a bit wary of
using them at all now as it affects the different batches/brands.

Mark H

Do you have any idea as to the capacitor manufacturer?

This problem isn't restricted to SM electrolytics, as a short google query confirmed.

 

[Ross Herbert]

On Sun, 15 Aug 2004 05:47:38 +1000, Bob Parker <bobp@bluebottle.com>
wrote:

|Hmmmmm,
| I thought it was fairly common knowledge that the most unreliable
|electronic components of all are SMD aluminium electrolytic caps...?
|They are the major cause of camcorders failing, for example.
| Someone once told me that NASA won't allow aluminium electrolytic
|caps to be used in any flight control systems on their spacecraft,
|which says something about what horrible components they are.
|
|Bob
|
Hey, ya can't knock aluminium electro's Bob. After all, we wouldn't
have a need for your ESR meter if they weren't so prone to failure,
would we?
-