SO14 package at 154C/W? Really?

[John Larkin]

On Fri, 05 Sep 2008 17:30:46 -0700, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Eric Smith wrote:
Joerg wrote:
A heatsink glued onto a BGA? Wow, that takes guts.

John Larkin wrote:
Guts? Why? It's soldered to the board in 456 places, which should be
pretty stiff.

Joerg wrote:
Yeah but if that number is reduced to 455 places some grief could set in

You'd have to be doing something extremely wrong in order for epoxying
a small heat sink to a properly soldered BGA to result in any of the
bonds failing. Are you applying the heat sink with a hammer or crowbar
or something?

We just use regular epoxy, gently squished down.

No, but I have seen too many BGA failures. Not in my designs because
(with one exception) I never used BGA.

Opposite experience. We've used hundreds of BGAs, mostly FG456's,
nearly all placed and soldered in-house, with exactly 100% success.

The only one we've ever removed and replaced was a couple of weeks
ago, and that was a mistake. There was a power plane short, nobody
could find it, so somebody decided to remove the BGA. NEEP! That
wasn't it. I dumped a 6-amp power supply into the plane and hit it
with the Flir imager... sure enough, a ceramic cap glowed in the
thermal IR... a simple solder bridge that nobody spotted.

We have a lot more trouble with TSSOPs and other fine-pitch leaded
parts. US8's are the pits. One nice thing about BGA solder joints is
that you can't inspect them, which saves a lot of production time.

It's liberating to have 200,000 gates and 300 i/o pins, in about a
square inch, at your disposal.

John

 

[Eeyore]

Joerg wrote:

Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read that the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself

I've NEVER known one take 16mA. I use 8mA as a guideline when estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e. 264 mW.

Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If no
limits are given you cannot use the part.

When you do medical for a few decades this stuff rattles on
automatically in the back of your head. You can't turn it off anymore ;-)

It didn't know it was one of those. I'll say however than the max figure seems
insane. Probably a left-over from an early data sheet revision.

Can you not use DIP or even SIL ? 5532's are available in SIL with a significant
board area decrease. I'm actually looking for some at the moment since they're not
widely known about.

Graham

 

[linnix]

On Sep 5, 6:51 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Fri, 05 Sep 2008 17:30:46 -0700, Joerg



notthisjoerg...@removethispacbell.net> wrote:
Eric Smith wrote:
Joerg wrote:
A heatsink glued onto a BGA? Wow, that takes guts.

John Larkin wrote:
Guts? Why? It's soldered to the board in 456 places, which should be
pretty stiff.

Joerg wrote:
Yeah but if that number is reduced to 455 places some grief could set in

You'd have to be doing something extremely wrong in order for epoxying
a small heat sink to a properly soldered BGA to result in any of the
bonds failing. Are you applying the heat sink with a hammer or crowbar
or something?

We just use regular epoxy, gently squished down.



No, but I have seen too many BGA failures. Not in my designs because
(with one exception) I never used BGA.

Opposite experience. We've used hundreds of BGAs, mostly FG456's,
nearly all placed and soldered in-house, with exactly 100% success.

The only one we've ever removed and replaced was a couple of weeks
ago, and that was a mistake. There was a power plane short, nobody
could find it, so somebody decided to remove the BGA. NEEP! That
wasn't it. I dumped a 6-amp power supply into the plane and hit it
with the Flir imager... sure enough, a ceramic cap glowed in the
thermal IR... a simple solder bridge that nobody spotted.

We have a lot more trouble with TSSOPs and other fine-pitch leaded
parts. US8's are the pits. One nice thing about BGA solder joints is
that you can't inspect them, which saves a lot of production time.

Same here, MLFs and QFNs are just as difficult to deal with in
production lines. We are skipping packagings all together. Chip On
Board (COG) die bonding is just as easily to order as anything else,
but usually 1K minimum.

It's liberating to have 200,000 gates and 300 i/o pins, in about a
square inch, at your disposal.

It's even better to be able to define your own footprints. We are
using a 68 pads die with 32 pins in one project and 44 pins in
another. They are just die bonded differently.

John

 

[th]

Joerg wrote:

Eeyore wrote:

Joerg wrote:

Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read that the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself

I've NEVER known one take 16mA. I use 8mA as a guideline when
estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e.
264 mW.


Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If no
limits are given you cannot use the part.

Don't you mix up hazard analysis with worst case analysis here? If the
data sheet says 16 mA and a part consumes only 8 mA over its operating
temperature range, it will not suddenly start consuming 16 mA just
because the data sheet says so. Depending on how many units you are
going to manufacture you can always buy a lot of parts and screen out
the ones exceeding your requirements, let's say 10 mA. Now use the
measured values and add some margin due to ageing effects in your WCA.

If you are doing an FMEA and are afraid of the part becoming to hot and
possibly causing a hazardous situation you anyway can't rely on the
data sheet since during a failure the part can consume much more than
listed in the data sheet. Thus you have to look at the current limit of
your power supply and the thermal properties of all parts connected to
that power supply that can generate hot spots in case of failure.

--
th

 

[Phil Hobbs]

Joerg wrote:

Eric Smith wrote:
Joerg wrote:
A heatsink glued onto a BGA? Wow, that takes guts.

John Larkin wrote:
Guts? Why? It's soldered to the board in 456 places, which should be
pretty stiff.

Joerg wrote:
Yeah but if that number is reduced to 455 places some grief could set
in

You'd have to be doing something extremely wrong in order for epoxying
a small heat sink to a properly soldered BGA to result in any of the
bonds failing. Are you applying the heat sink with a hammer or crowbar
or something?


No, but I have seen too many BGA failures. Not in my designs because
(with one exception) I never used BGA.

Dropping the board just once is often enough--the acceleration during
impact is

a = g*(height of fall)/(crumple distance)

which can easily be thousands of times g, especially on hard floors.

Our server blades have to pass a 3000g shock test, which is really tough
if there's no compliant layer (such as paste or liquid metal) between
the HS and the processor. C4 balls are under a lot of static stress to
begin with (although little ones with under 500 connections are easier
than large ones).

Cheers,

Phil Hobbs

 

[Joerg]

Eeyore wrote:

Joerg wrote:

Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read that the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself
I've NEVER known one take 16mA. I use 8mA as a guideline when estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e. 264 mW.
Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If no
limits are given you cannot use the part.

When you do medical for a few decades this stuff rattles on
automatically in the back of your head. You can't turn it off anymore ;-)

It didn't know it was one of those. I'll say however than the max figure seems
insane. Probably a left-over from an early data sheet revision.

Can you not use DIP or even SIL ? 5532's are available in SIL with a significant
board area decrease. I'm actually looking for some at the moment since they're not
widely known about.

No, only SMT. But why should I? The old Motorola amp works, uses a lot
less power and ONSemi keeps making tons of them. Plus has ST as a 2nd
source.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Joerg]

th wrote:

Joerg wrote:
Eeyore wrote:

Joerg wrote:

Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read that
the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps
each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in
SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself

I've NEVER known one take 16mA. I use 8mA as a guideline when
estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e.
264 mW.


Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If no
limits are given you cannot use the part.


Don't you mix up hazard analysis with worst case analysis here? If the
data sheet says 16 mA and a part consumes only 8 mA over its operating
temperature range, it will not suddenly start consuming 16 mA just
because the data sheet says so. Depending on how many units you are
going to manufacture you can always buy a lot of parts and screen out
the ones exceeding your requirements, let's say 10 mA. Now use the
measured values and add some margin due to ageing effects in your WCA.

No cherry picking in this business.

If you are doing an FMEA and are afraid of the part becoming to hot and
possibly causing a hazardous situation you anyway can't rely on the
data sheet since during a failure the part can consume much more than
listed in the data sheet. Thus you have to look at the current limit of
your power supply and the thermal properties of all parts connected to
that power supply that can generate hot spots in case of failure.

I know, that's all in the hazard analysis. What I meant is that if you
design in parts assuming "typical datasheet values" it's only a matter
of time until the FDA has you over the barrel.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Joerg]

John Larkin wrote:

On Fri, 05 Sep 2008 17:30:46 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Eric Smith wrote:
Joerg wrote:
A heatsink glued onto a BGA? Wow, that takes guts.
John Larkin wrote:
Guts? Why? It's soldered to the board in 456 places, which should be
pretty stiff.
Joerg wrote:
Yeah but if that number is reduced to 455 places some grief could set in
You'd have to be doing something extremely wrong in order for epoxying
a small heat sink to a properly soldered BGA to result in any of the
bonds failing. Are you applying the heat sink with a hammer or crowbar
or something?

We just use regular epoxy, gently squished down.

No, but I have seen too many BGA failures. Not in my designs because
(with one exception) I never used BGA.

Opposite experience. We've used hundreds of BGAs, mostly FG456's,
nearly all placed and soldered in-house, with exactly 100% success.

The only one we've ever removed and replaced was a couple of weeks
ago, and that was a mistake. There was a power plane short, nobody
could find it, so somebody decided to remove the BGA. NEEP! That
wasn't it. I dumped a 6-amp power supply into the plane and hit it
with the Flir imager... sure enough, a ceramic cap glowed in the
thermal IR... a simple solder bridge that nobody spotted.

We have a lot more trouble with TSSOPs and other fine-pitch leaded
parts. US8's are the pits. One nice thing about BGA solder joints is
that you can't inspect them, which saves a lot of production time.

It's liberating to have 200,000 gates and 300 i/o pins, in about a
square inch, at your disposal.

If you ever do a garage sale and that FLIR camera is part of it let me
know

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[John Larkin]

On Sat, 06 Sep 2008 08:29:37 -0700, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

John Larkin wrote:
On Fri, 05 Sep 2008 17:30:46 -0700, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Eric Smith wrote:
Joerg wrote:
A heatsink glued onto a BGA? Wow, that takes guts.
John Larkin wrote:
Guts? Why? It's soldered to the board in 456 places, which should be
pretty stiff.
Joerg wrote:
Yeah but if that number is reduced to 455 places some grief could set in
You'd have to be doing something extremely wrong in order for epoxying
a small heat sink to a properly soldered BGA to result in any of the
bonds failing. Are you applying the heat sink with a hammer or crowbar
or something?

We just use regular epoxy, gently squished down.

No, but I have seen too many BGA failures. Not in my designs because
(with one exception) I never used BGA.

Opposite experience. We've used hundreds of BGAs, mostly FG456's,
nearly all placed and soldered in-house, with exactly 100% success.

The only one we've ever removed and replaced was a couple of weeks
ago, and that was a mistake. There was a power plane short, nobody
could find it, so somebody decided to remove the BGA. NEEP! That
wasn't it. I dumped a 6-amp power supply into the plane and hit it
with the Flir imager... sure enough, a ceramic cap glowed in the
thermal IR... a simple solder bridge that nobody spotted.

We have a lot more trouble with TSSOPs and other fine-pitch leaded
parts. US8's are the pits. One nice thing about BGA solder joints is
that you can't inspect them, which saves a lot of production time.

It's liberating to have 200,000 gates and 300 i/o pins, in about a
square inch, at your disposal.


If you ever do a garage sale and that FLIR camera is part of it let me
know

You will have to pry my thermal imager gun out of my 21.34 degree C
dead hands.

John

 

[Eeyore]

Joerg wrote:

Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read that the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself
I've NEVER known one take 16mA. I use 8mA as a guideline when estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e. 264 mW.
Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If no
limits are given you cannot use the part.

When you do medical for a few decades this stuff rattles on
automatically in the back of your head. You can't turn it off anymore ;-)

It didn't know it was one of those. I'll say however than the max figure seems
insane. Probably a left-over from an early data sheet revision.

Can you not use DIP or even SIL ? 5532's are available in SIL with a significant
board area decrease. I'm actually looking for some at the moment since they're not
widely known about.

No, only SMT. But why should I? The old Motorola amp works, uses a lot
less power and ONSemi keeps making tons of them. Plus has ST as a 2nd
source.

But I thought your initial question was whether the MOT part was suitable ? Yet the
supply current is in the 100s of uA !

Where did you you get you 400 odd mW from ?

Graham

 

[Joerg]

Eeyore wrote:

Joerg wrote:

Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read that the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself
I've NEVER known one take 16mA. I use 8mA as a guideline when estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e. 264 mW.
Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If no
limits are given you cannot use the part.

When you do medical for a few decades this stuff rattles on
automatically in the back of your head. You can't turn it off anymore ;-)
It didn't know it was one of those. I'll say however than the max figure seems
insane. Probably a left-over from an early data sheet revision.

Can you not use DIP or even SIL ? 5532's are available in SIL with a significant
board area decrease. I'm actually looking for some at the moment since they're not
widely known about.
No, only SMT. But why should I? The old Motorola amp works, uses a lot
less power and ONSemi keeps making tons of them. Plus has ST as a 2nd
source.

But I thought your initial question was whether the MOT part was suitable ? Yet the
supply current is in the 100s of uA !

But not 1000s of uA line the 5532.

Where did you you get you 400 odd mW from ?

I need another 2mA per output from each amp at almost 40V supply. Might
be able to squeeze it down to 1mA or less.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[th]

Joerg wrote:

th wrote:
Joerg wrote:
Eeyore wrote:

Joerg wrote:

Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read
that the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps
each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in
SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself


I've NEVER known one take 16mA. I use 8mA as a guideline when
estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e.
264 mW.


Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If
no limits are given you cannot use the part.


Don't you mix up hazard analysis with worst case analysis here? If the
data sheet says 16 mA and a part consumes only 8 mA over its operating
temperature range, it will not suddenly start consuming 16 mA just
because the data sheet says so. Depending on how many units you are
going to manufacture you can always buy a lot of parts and screen out
the ones exceeding your requirements, let's say 10 mA. Now use the
measured values and add some margin due to ageing effects in your WCA.


No cherry picking in this business.

It is not cherry picking if you write a proper specification with your
specific values and buy the parts via an independent test house. They
typically charge you a few dollars per device in test costs plus a fixed
sum for the test setup. Could be worth looking into that alternative
depending on your volumes.

This is the same procedure as the microprocessor manufacturers use,
except that they do the screening in-house. There is no physical
difference between a 2 GHz and a 2.4 GHz processor, it just happens
that some wafer lots end up faster than others during manufacturing.

--
th

 

[Joerg]

th wrote:

Joerg wrote:
th wrote:
Joerg wrote:
Eeyore wrote:

Joerg wrote:

Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read
that the
usual SO14 package is only rated at 154C/W. Since I am burning
500mW
that would become too toasty, ouch. Or I'll have to idle two
amps each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in
SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder
itself

I've NEVER known one take 16mA. I use 8mA as a guideline when
estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e.
264 mW.


Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If
no limits are given you cannot use the part.


Don't you mix up hazard analysis with worst case analysis here? If
the data sheet says 16 mA and a part consumes only 8 mA over its
operating temperature range, it will not suddenly start consuming 16
mA just because the data sheet says so. Depending on how many units
you are going to manufacture you can always buy a lot of parts and
screen out the ones exceeding your requirements, let's say 10 mA. Now
use the measured values and add some margin due to ageing effects in
your WCA.


No cherry picking in this business.


It is not cherry picking if you write a proper specification with your
specific values and buy the parts via an independent test house. They
typically charge you a few dollars per device in test costs plus a fixed
sum for the test setup. Could be worth looking into that alternative
depending on your volumes.

"a few Dollars per device" would be the killer here. Medical might be a
lucrative market but not that lucrative ;-)

This is the same procedure as the microprocessor manufacturers use,
except that they do the screening in-house. There is no physical
difference between a 2 GHz and a 2.4 GHz processor, it just happens
that some wafer lots end up faster than others during manufacturing.

But then they are shipped with different part numbers. In medical you'd
have to also laser-mark the devices. Anyhow, I really never do that but
always look for a solution that works with off-the-shelf part. A
solution which I now have, by using MC33171 amps. Same as the MC33174
but singles instead of quads. Cheap, works.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[John Larkin]

On Sat, 6 Sep 2008 23:24:06 +0000 (UTC), Andre Majorel
<cheney@halliburton.com> wrote:

On 2008-09-06, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

One nice thing about BGA solder joints is that you can't
inspect them, which saves a lot of production time.

I thought it was done, with X rays or something ?

It can be, and was more often when BGAs were new. There are also some
optical things that can peek under the chips and let you see 4 or 5
balls deep, and also look for crud between the rows. We actually have
one of those, and my production people sometimes use it, mostly to see
that their temperature profiles look right, that the solder has flowed
nicely. But once a process is up and boards are flowing down the line,
individual board inspection isn't commonly done, by us or by our
outside contractors. Like I said, we've scored 100% so far.

I think I could program a BGA to inspect its own solder joints, by
measuring pin capacitance. Maybe I'll do that some day.

John

 

[John Larkin]

On Sat, 06 Sep 2008 11:08:16 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Joerg wrote:
Eric Smith wrote:
Joerg wrote:
A heatsink glued onto a BGA? Wow, that takes guts.

John Larkin wrote:
Guts? Why? It's soldered to the board in 456 places, which should be
pretty stiff.

Joerg wrote:
Yeah but if that number is reduced to 455 places some grief could set
in

You'd have to be doing something extremely wrong in order for epoxying
a small heat sink to a properly soldered BGA to result in any of the
bonds failing. Are you applying the heat sink with a hammer or crowbar
or something?


No, but I have seen too many BGA failures. Not in my designs because
(with one exception) I never used BGA.


Dropping the board just once is often enough--the acceleration during
impact is

a = g*(height of fall)/(crumple distance)

which can easily be thousands of times g, especially on hard floors.

Our server blades have to pass a 3000g shock test, which is really tough
if there's no compliant layer (such as paste or liquid metal) between
the HS and the processor. C4 balls are under a lot of static stress to
begin with (although little ones with under 500 connections are easier
than large ones).

Cheers,

Phil Hobbs

I'd suspect that board flex could be a killer in high-shock
situations, or where a lot of force is applied by a heatsink clamp or
some such. Gluing a fairly light pin-fin heat sink to the top of a bga
FPGA doesn't seem very hazardous to me.

No problems so far.

John

 

[Phil Hobbs]

John Larkin wrote:

On Sat, 06 Sep 2008 11:08:16 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Joerg wrote:
Eric Smith wrote:
Joerg wrote:
A heatsink glued onto a BGA? Wow, that takes guts.
John Larkin wrote:
Guts? Why? It's soldered to the board in 456 places, which should be
pretty stiff.
Joerg wrote:
Yeah but if that number is reduced to 455 places some grief could set
in
You'd have to be doing something extremely wrong in order for epoxying
a small heat sink to a properly soldered BGA to result in any of the
bonds failing. Are you applying the heat sink with a hammer or crowbar
or something?

No, but I have seen too many BGA failures. Not in my designs because
(with one exception) I never used BGA.

Dropping the board just once is often enough--the acceleration during
impact is

a = g*(height of fall)/(crumple distance)

which can easily be thousands of times g, especially on hard floors.

Our server blades have to pass a 3000g shock test, which is really tough
if there's no compliant layer (such as paste or liquid metal) between
the HS and the processor. C4 balls are under a lot of static stress to
begin with (although little ones with under 500 connections are easier
than large ones).

Cheers,

Phil Hobbs

I'd suspect that board flex could be a killer in high-shock
situations, or where a lot of force is applied by a heatsink clamp or
some such. Gluing a fairly light pin-fin heat sink to the top of a bga
FPGA doesn't seem very hazardous to me.

No problems so far.

Yours are probably fine (and your customers seem to be technical folk
who probably don't expect badly dinged hardware to still work). Some of
our heatsinks weigh pounds apiece, and that 3000g test is no joke.

Cheers,

Phil Hobbs

 

[Phil Hobbs]

John Larkin wrote:

On Sat, 6 Sep 2008 23:24:06 +0000 (UTC), Andre Majorel
cheney@halliburton.com> wrote:

On 2008-09-06, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

One nice thing about BGA solder joints is that you can't
inspect them, which saves a lot of production time.
I thought it was done, with X rays or something ?

It can be, and was more often when BGAs were new. There are also some
optical things that can peek under the chips and let you see 4 or 5
balls deep, and also look for crud between the rows. We actually have
one of those, and my production people sometimes use it, mostly to see
that their temperature profiles look right, that the solder has flowed
nicely. But once a process is up and boards are flowing down the line,
individual board inspection isn't commonly done, by us or by our
outside contractors. Like I said, we've scored 100% so far.

I think I could program a BGA to inspect its own solder joints, by
measuring pin capacitance. Maybe I'll do that some day.

John

We actually have a CT scanner for this up in Poughkeepsie. Takes a
pretty long time when there are high atomic weight metals in the way, so
iiuc it's used for sample testing and failure analysis--hopefully the
failures happen during qualification and not in the field!

Cheers,

Phil Hobbs

 

[Andre Majorel]

On 2008-09-06, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

One nice thing about BGA solder joints is that you can't
inspect them, which saves a lot of production time.

I thought it was done, with X rays or something ?

--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
"Je regrette le Concorde. Au moins il vous amenait directement ŕ
l'hôtel." -- Cyrano

 

[Eeyore]

Joerg wrote:

Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read that the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself
I've NEVER known one take 16mA. I use 8mA as a guideline when estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e. 264 mW.
Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If no
limits are given you cannot use the part.

When you do medical for a few decades this stuff rattles on
automatically in the back of your head. You can't turn it off anymore ;-)
It didn't know it was one of those. I'll say however than the max figure seems
insane. Probably a left-over from an early data sheet revision.

Can you not use DIP or even SIL ? 5532's are available in SIL with a significant
board area decrease. I'm actually looking for some at the moment since they're not
widely known about.
No, only SMT. But why should I? The old Motorola amp works, uses a lot
less power and ONSemi keeps making tons of them. Plus has ST as a 2nd
source.

But I thought your initial question was whether the MOT part was suitable ? Yet the
supply current is in the 100s of uA !

But not 1000s of uA line the 5532.

Where did you you get you 400 odd mW from ?

I need another 2mA per output from each amp at almost 40V supply. Might
be able to squeeze it down to 1mA or less.

So it's all load related. Why not buffer the outputs with a couple of discretes (or one if
it's only unipolar ?). Is it that tight for space ?

Graham

 

[Joerg]

Eeyore wrote:

Joerg wrote:

Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:
Eeyore wrote:
Joerg wrote:

So here I am, needing more than the usual 32V opamp. Chose ye olde
MC33174 because it can take 44V but was surprised when I read that the
usual SO14 package is only rated at 154C/W. Since I am burning 500mW
that would become too toasty, ouch. Or I'll have to idle two amps each
in there and double the number of chips.

So, is 500mW in a SO14 really too much? What do thee say?
NE5532 ? That's rated at +/- 22V IIRC. I think I've seen them in SMT in
recent years.

Large input bias current IIRC though.
Max supply current is 16mA. At 40V VCC it'll almost unsolder itself
I've NEVER known one take 16mA. I use 8mA as a guideline when estimating PSU
requirements (TI typical 352mW). Typical from Fairchild is 6mA i.e. 264 mW.
Yes, sure, but this is a medical design. There you must always do a
hazard analysis (FMEA and all that) and assume datasheet limits. If no
limits are given you cannot use the part.

When you do medical for a few decades this stuff rattles on
automatically in the back of your head. You can't turn it off anymore ;-)
It didn't know it was one of those. I'll say however than the max figure seems
insane. Probably a left-over from an early data sheet revision.

Can you not use DIP or even SIL ? 5532's are available in SIL with a significant
board area decrease. I'm actually looking for some at the moment since they're not
widely known about.
No, only SMT. But why should I? The old Motorola amp works, uses a lot
less power and ONSemi keeps making tons of them. Plus has ST as a 2nd
source.
But I thought your initial question was whether the MOT part was suitable ? Yet the
supply current is in the 100s of uA !
But not 1000s of uA line the 5532.

Where did you you get you 400 odd mW from ?
I need another 2mA per output from each amp at almost 40V supply. Might
be able to squeeze it down to 1mA or less.

So it's all load related. Why not buffer the outputs with a couple of discretes (or one if
it's only unipolar ?). Is it that tight for space ?

In this case that means 30 more parts to place, versus 12 if I just use
single opamps.

--
Regards, Joerg

http://www.analogconsultants.com/

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