This is cool:
https://www.ti.com/lit/pdf/slyy245?keyMatch=slyy245.pdf&tisearch=universal_search
Imagine that the gold wirebonds cost more than the chip.
Some of the new mosfet and ganfet packages are great, if impossible to
solder by hand. The source-down things are great for low-inductance low-thermal packaging... you can solder the source to your ground
plane.
I run into problems with long term reliability of SMD LED driver chips where the solder junctions fail. In a particular application this is likely the result of long term exposure to heat/cool cycles and weather where the logic board is exposed to twisting tension where it is screwed to an aluminum tower that is fifteen meters or so tall. This is a set of 40 - 8 x 8 LED matrix (about 30cm square panel) displays for a Hi-Striker game found at amusement parks where you smack a pedestal with a hammer and see how high the indicator goes. I am somewhat of the opinion that DIP packages solder connections would survive longer than SMD under the same exposure.
https://www.highwaygames.com/arcade-machines/american-hi-striker-6070/
This tower was made in the late 90s and started breaking down around five years
ago. I've gone through most of the boards replacing failing connectors and re-soldering (63/37) the SMD devices after clearing the conformal coating off.
I want to make new panels to replace the old ones as the 8 x 8 LED legs are rotting off on most panels and they are going to finally fail within another five years. So trying to figure out what will be most likely to survive for perhaps another twenty years of outdoor exposure...
On 2025-07-25 8:31 a.m., Don Y wrote:
On 7/25/2025 7:52 AM, John Robertson wrote:
I run into problems with long term reliability of SMD LED driver chips
where the solder junctions fail. In a particular application this is
likely the result of long term exposure to heat/cool cycles and
weather where the logic board is exposed to twisting tension where it
is screwed to an aluminum tower that is fifteen meters or so tall.
This is a set of 40 - 8 x 8 LED matrix (23x20cm panel)
displays for a Hi-Striker game found at amusement parks where you
smack a pedestal with a hammer and see how high the indicator goes. I
am somewhat of the opinion that DIP packages solder connections would
survive longer than SMD under the same exposure.
https://www.highwaygames.com/arcade-machines/american-hi-striker-6070/
This tower was made in the late 90s and started breaking down around
five years ago. I've gone through most of the boards replacing failing
connectors and re-soldering (63/37) the SMD devices after clearing the
conformal coating off.
Is it a semi-permanent installation? Or, something that is set up and
taken down as the show moves around (or seasons end)?
Semi-Permanent - it sits outdoors from April through early November, and
then is stored under cover at outdoor temperatures. This is Vancouver,
BC, so coolest shade temp is perhaps -10C and hottest is 40C (rare,
closer to max of 35C in the few really hot [what we call hot!] days in >summer), it does rain though...
When I was doing grey-area boxes, I would use 100 or 120 mil boards just
to protect against the abuse they would see on location. A lot stiffer
than the 60 mil boards. For long-leaded thru hole parts, the extra
thickness wouldn't be a challenge (though DIPs might need a bit of a
reach)
That is an excellent point, I can certainly make thicker boards. That
will greatly reduce the flex...
Can you stiffen the tower (aluminum is pretty flimsy) without unduly
adding weight (esp if not a permanent installation)? And, possibly
isolate it from the transducer so hammer strikes don't send vibrations
up the display?
No, the tower is secured halfway up and near the top to a steel "H"
frame but it can still flex a smidgen in the wind, and when it is taken
down for storage... No guy wires securing it.
Photos here:
https://www.dropbox.com/scl/fo/c6jtops8rkree0zzb20ck/AMltrD8EAmYnzyzcndj58Y8?rlkey=alysdnmf83ywmb391jl2t7pxb&dl=0
I want to make new panels to replace the old ones as the 8 x 8 LEDAre you planning on replacing the "LED modules"? Or, the assembly that
legs are rotting off on most panels and they are going to finally fail
within another five years. So trying to figure out what will be most
likely to survive for perhaps another twenty years of outdoor exposure... >>
ties
them together (wired connector arrays)?
The LEDs are in 8 columns with each panel having 8 X A6275 Allegro 8-Bit >Serial Input Constant-Current Latched LED Drivers. Obsolete but
replaceable easily enough. The original design has 8 LEDs per 'pixel' in
a 4 x 4 array. My plan is to replace the 8 LEDs with a single high
intensity RED modular LED so it is easily seen in daylight.
You might consider potting the LED assemblies -- including front and back
of board with just a connector body protruding.
Potting might not survive rough handling...
DIP has always been easier to deal with in the field in that sort of
market.
A lot easier to design kit that sits in a nice air conditioned lab, eh? :> >>
Oh yes, the real world is a scary place for electronics and other creatures!
Thanks!
John :-#)#
On 2025-07-25 8:31 a.m., Don Y wrote:
On 7/25/2025 7:52 AM, John Robertson wrote:
I run into problems with long term reliability of SMD LED driver chips
where the solder junctions fail. In a particular application this is
likely the result of long term exposure to heat/cool cycles and
weather where the logic board is exposed to twisting tension where it
is screwed to an aluminum tower that is fifteen meters or so tall.
This is a set of 40 - 8 x 8 LED matrix (23x20cm panel)
displays for a Hi-Striker game found at amusement parks where you
smack a pedestal with a hammer and see how high the indicator goes. I
am somewhat of the opinion that DIP packages solder connections would
survive longer than SMD under the same exposure.
https://www.highwaygames.com/arcade-machines/american-hi-striker-6070/
This tower was made in the late 90s and started breaking down around
five years ago. I've gone through most of the boards replacing failing
connectors and re-soldering (63/37) the SMD devices after clearing the
conformal coating off.
Is it a semi-permanent installation? Or, something that is set up and
taken down as the show moves around (or seasons end)?
Semi-Permanent - it sits outdoors from April through early November, and
then is stored under cover at outdoor temperatures. This is Vancouver,
BC, so coolest shade temp is perhaps -10C and hottest is 40C (rare,
closer to max of 35C in the few really hot [what we call hot!] days in >summer), it does rain though...
When I was doing grey-area boxes, I would use 100 or 120 mil boards just
to protect against the abuse they would see on location. A lot stiffer
than the 60 mil boards. For long-leaded thru hole parts, the extra
thickness wouldn't be a challenge (though DIPs might need a bit of a
reach)
That is an excellent point, I can certainly make thicker boards. That
will greatly reduce the flex...
Can you stiffen the tower (aluminum is pretty flimsy) without unduly
adding weight (esp if not a permanent installation)? And, possibly
isolate it from the transducer so hammer strikes don't send vibrations
up the display?
No, the tower is secured halfway up and near the top to a steel "H"
frame but it can still flex a smidgen in the wind, and when it is taken
down for storage... No guy wires securing it.
Photos here:
https://www.dropbox.com/scl/fo/c6jtops8rkree0zzb20ck/AMltrD8EAmYnzyzcndj58Y8?rlkey=alysdnmf83ywmb391jl2t7pxb&dl=0
I want to make new panels to replace the old ones as the 8 x 8 LEDAre you planning on replacing the "LED modules"? Or, the assembly that
legs are rotting off on most panels and they are going to finally fail
within another five years. So trying to figure out what will be most
likely to survive for perhaps another twenty years of outdoor exposure... >>
ties
them together (wired connector arrays)?
The LEDs are in 8 columns with each panel having 8 X A6275 Allegro 8-Bit >Serial Input Constant-Current Latched LED Drivers. Obsolete but
replaceable easily enough. The original design has 8 LEDs per 'pixel' in
a 4 x 4 array. My plan is to replace the 8 LEDs with a single high
intensity RED modular LED so it is easily seen in daylight.
You might consider potting the LED assemblies -- including front and back
of board with just a connector body protruding.
Potting might not survive rough handling...
Is it a semi-permanent installation? Or, something that is set up and
taken down as the show moves around (or seasons end)?
Semi-Permanent - it sits outdoors from April through early November, and then is stored under cover at outdoor temperatures.
This is Vancouver, BC, so
coolest shade temp is perhaps -10C and hottest is 40C (rare, closer to max of 35C in the few really hot [what we call hot!] days in summer), it does rain though...
When I was doing grey-area boxes, I would use 100 or 120 mil boards just
to protect against the abuse they would see on location. A lot stiffer
than the 60 mil boards. For long-leaded thru hole parts, the extra
thickness wouldn't be a challenge (though DIPs might need a bit of a
reach)
That is an excellent point, I can certainly make thicker boards. That will greatly reduce the flex...
Can you stiffen the tower (aluminum is pretty flimsy) without unduly
adding weight (esp if not a permanent installation)? And, possibly
isolate it from the transducer so hammer strikes don't send vibrations
up the display?
No, the tower is secured halfway up and near the top to a steel "H" frame but it can still flex a smidgen in the wind, and when it is taken down for storage... No guy wires securing it.
Photos here:
https://www.dropbox.com/scl/fo/c6jtops8rkree0zzb20ck/AMltrD8EAmYnzyzcndj58Y8?rlkey=alysdnmf83ywmb391jl2t7pxb&dl=0
I want to make new panels to replace the old ones as the 8 x 8 LED legs are >>> rotting off on most panels and they are going to finally fail within another
five years. So trying to figure out what will be most likely to survive for >>> perhaps another twenty years of outdoor exposure...
Are you planning on replacing the "LED modules"? Or, the assembly that ties
them together (wired connector arrays)?
The LEDs are in 8 columns with each panel having 8 X A6275 Allegro 8-Bit Serial
Input Constant-Current Latched LED Drivers. Obsolete but replaceable easily enough. The original design has 8 LEDs per 'pixel' in a 4 x 4 array. My plan is
to replace the 8 LEDs with a single high intensity RED modular LED so it is easily seen in daylight.
You might consider potting the LED assemblies -- including front and back
of board with just a connector body protruding.
Potting might not survive rough handling...
DIP has always been easier to deal with in the field in that sort of market. >>
A lot easier to design kit that sits in a nice air conditioned lab, eh? :>
Oh yes, the real world is a scary place for electronics and other creatures!
I run into problems with long term reliability of SMD LED driver chips where the solder junctions fail. \
... I am somewhat of the opinion that DIP packages solder connections would survive longer than SMD under the same exposure.
On 7/25/2025 7:52 AM, John Robertson wrote:
I run into problems with long term reliability of SMD LED driver chips
where the solder junctions fail. \
... I am somewhat of the opinion that DIP packages solder connections
would survive longer than SMD under the same exposure.
I try not to rely solely upon solder for mechanical connections of large through hole parts because of the greater stress they experience due to
the larger mass. In your application, even small parts are under stress.
Should you be gluing these parts down before you solder so the solder
joints are not going to be under stress as the only mechanical hold downs?
On 31/07/2025 07:28, John Robertson wrote:
On 2025-07-30 9:06 a.m., Buzz McCool wrote:You could increase the area of the surface mount pads so that more
On 7/25/2025 7:52 AM, John Robertson wrote:
I run into problems with long term reliability of SMD LED driver
chips where the solder junctions fail. \
... I am somewhat of the opinion that DIP packages solder
connections would survive longer than SMD under the same exposure.
I try not to rely solely upon solder for mechanical connections of
large through hole parts because of the greater stress they
experience due to the larger mass. In your application, even small
parts are under stress.
Should you be gluing these parts down before you solder so the solder
joints are not going to be under stress as the only mechanical hold
downs?
I don't know if gluing them down will help. I think reducing the size
of the SMD devices will reduce the PCB solder stress fracture risk
though.
John :-#)#
solder paste is available, giving a thicker solder fillet.
Is it possible to add stiffener bars to the pcbs to reduce flexing?
John
On 2025-07-30 9:06 a.m., Buzz McCool wrote:
On 7/25/2025 7:52 AM, John Robertson wrote:
I run into problems with long term reliability of SMD LED driver chips
where the solder junctions fail. \
... I am somewhat of the opinion that DIP packages solder connections
would survive longer than SMD under the same exposure.
I try not to rely solely upon solder for mechanical connections of large
through hole parts because of the greater stress they experience due to
the larger mass. In your application, even small parts are under stress.
Should you be gluing these parts down before you solder so the solder
joints are not going to be under stress as the only mechanical hold downs?
I don't know if gluing them down will help. I think reducing the size of
the SMD devices will reduce the PCB solder stress fracture risk though.
| Sysop: | Keyop |
|---|---|
| Location: | Huddersfield, West Yorkshire, UK |
| Users: | 546 |
| Nodes: | 16 (2 / 14) |
| Uptime: | 50:22:15 |
| Calls: | 10,397 |
| Calls today: | 5 |
| Files: | 14,067 |
| Messages: | 6,417,317 |
| Posted today: | 1 |