• How to protect circuit boards that must be exposed to weather?

    From John Robertson@21:1/5 to All on Thu Aug 1 17:50:29 2024
    I have another problem - display panels on an outdoor hammer game - the
    style that you swing a hammer at a pedestal and it lights up a column of
    LED panels with 8x8 graphics.

    The one I am repairing was made in 2001 and it is breaking down. The
    surface mounted serial drivers are loosing connection to the PCBs from
    being thermally stressed over a couple of decades of outdoor use and I
    want to make replacement panels (the original company has abandoned the product) that will be more durable.

    Currently on the rear (somewhat protected) side of the board is the electronics, covered (or course) with a conformal coating. The outer
    side is an 8 X 8 matrix of LEDs in groups of 8 for each pixel of the 64
    pixels on the panel.

    There are 40 - 8 x 8.75 inch panels going up around 30 feet...

    Is there a better way to solder on SMD devices to help avoid thermal
    solder failure? After connection corrosion, the biggest problem is
    solder failure of the SMD pads to the PCBs.

    Thanks!

    John :-#)#
    --
    (Please post followups or tech inquiries to the USENET newsgroup)
    John's Jukes Ltd.
    #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
    (604)872-5757 (Pinballs, Jukes, Video Games)
    www.flippers.com
    "Old pinballers never die, they just flip out."

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  • From Don Y@21:1/5 to John Robertson on Thu Aug 1 19:35:00 2024
    On 8/1/2024 5:50 PM, John Robertson wrote:
    I have another problem - display panels on an outdoor hammer game - the style that you swing a hammer at a pedestal and it lights up a column of LED panels with 8x8 graphics.

    The one I am repairing was made in 2001 and it is breaking down. The surface mounted serial drivers are loosing connection to the PCBs from being thermally
    stressed over a couple of decades of outdoor use and I want to make replacement
    panels (the original company has abandoned the product) that will be more durable.

    Currently on the rear (somewhat protected) side of the board is the electronics, covered (or course) with a conformal coating. The outer side is an
    8 X 8 matrix of LEDs in groups of 8 for each pixel of the 64 pixels on the panel.

    There are 40 - 8 x 8.75 inch panels going up around 30 feet...

    Is there a better way to solder on SMD devices to help avoid thermal solder failure? After connection corrosion, the biggest problem is solder failure of the SMD pads to the PCBs.

    If you are "reimplementing" the design, you might opt for thru-hole
    devices and leaded solder. (Or, perhaps a piggyback board that
    does this and ties into the existing board)

    But, 20+ years for something exposed to the out-of-doors is a good
    run. When I was designing KWHr meters, we targeted a 30 year life
    but the LCD displays invariably shit the bed early (because you can't
    ensure the device will be installed in a "protected" space).

    Is there anything wrong with just "refreshing" the product and hoping
    for ANOTHER 20 years?

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  • From Jan Panteltje@21:1/5 to jrr@flippers.com on Fri Aug 2 05:27:16 2024
    On a sunny day (Thu, 1 Aug 2024 17:50:29 -0700) it happened John Robertson <jrr@flippers.com> wrote in <v8hagn$2f8eq$1@dont-email.me>:

    I have another problem - display panels on an outdoor hammer game - the
    style that you swing a hammer at a pedestal and it lights up a column of
    LED panels with 8x8 graphics.

    The one I am repairing was made in 2001 and it is breaking down. The
    surface mounted serial drivers are loosing connection to the PCBs from
    being thermally stressed over a couple of decades of outdoor use and I
    want to make replacement panels (the original company has abandoned the >product) that will be more durable.

    Currently on the rear (somewhat protected) side of the board is the >electronics, covered (or course) with a conformal coating. The outer
    side is an 8 X 8 matrix of LEDs in groups of 8 for each pixel of the 64 >pixels on the panel.

    There are 40 - 8 x 8.75 inch panels going up around 30 feet...

    Is there a better way to solder on SMD devices to help avoid thermal
    solder failure? After connection corrosion, the biggest problem is
    solder failure of the SMD pads to the PCBs.

    I have this Motec satellite dish positioner, bought around year 2000,
    sits outside in the very cold (freezing) and very hot (glowball worming) weather,
    has GHz electronics and connectors, and motor drive electronics.
    Never ever failed.
    I once opened it up, it was covered (the electronics) in what looks like candle wax...
    I wanted to see something about the motor drive (curiosity) and pressed my scope probe point through the wax.
    Did I melt it gain? Dunno, but it still works 100% every day.

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  • From Buzz McCool@21:1/5 to John Robertson on Fri Aug 2 07:44:47 2024
    On 8/1/2024 5:50 PM, John Robertson wrote:
    Is there a better way to solder on SMD devices to help avoid thermal
    solder failure?

    Underfill

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  • From Glen Walpert@21:1/5 to John Robertson on Tue Aug 6 22:27:09 2024
    On Thu, 1 Aug 2024 17:50:29 -0700, John Robertson wrote:

    I have another problem - display panels on an outdoor hammer game - the
    style that you swing a hammer at a pedestal and it lights up a column of
    LED panels with 8x8 graphics.

    The one I am repairing was made in 2001 and it is breaking down. The
    surface mounted serial drivers are loosing connection to the PCBs from
    being thermally stressed over a couple of decades of outdoor use and I
    want to make replacement panels (the original company has abandoned the product) that will be more durable.

    Currently on the rear (somewhat protected) side of the board is the electronics, covered (or course) with a conformal coating. The outer
    side is an 8 X 8 matrix of LEDs in groups of 8 for each pixel of the 64 pixels on the panel.

    There are 40 - 8 x 8.75 inch panels going up around 30 feet...

    Is there a better way to solder on SMD devices to help avoid thermal
    solder failure? After connection corrosion, the biggest problem is
    solder failure of the SMD pads to the PCBs.

    Thanks!

    John :-#)#

    If the column of lights is attached to the same base as the hammer target, there could be significant solder fatigue from the vibrations traveling up
    the light column.

    Switching to lead-free will improve fatigue resistance. While there are lead-free alloys specifically designed for good fatigue resistance, and
    any solder mfgr app engineer could make a recommendation, the standard
    SAC305 is a significant improvement over tin-lead according to numerous
    test results published in the industry trade magazines like SMT
    Technology.

    Stiffening the boards with a thicker material or with stiffeners will
    reduce thermal bowing from sunshine. Leaving all unused area covered with copper ground plane and white or light colored soldermask might help.

    Flexible mounting to isolate vibration might help, perhaps clamp between silicone foam strips with rubber bushings around the screws or similar,
    could also provide sealing of the back side.

    Flexible conformal coating will prevent the coating from stressing solder,
    as can happen with rigid materials due to differential thermal expansion.

    As Buzz mentioned, underfill can help if your assembler has the
    capability.

    Regards,
    Glen

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  • From John Robertson@21:1/5 to Glen Walpert on Wed Aug 7 14:34:14 2024
    On 2024-08-06 3:27 p.m., Glen Walpert wrote:
    On Thu, 1 Aug 2024 17:50:29 -0700, John Robertson wrote:

    I have another problem - display panels on an outdoor hammer game - the
    style that you swing a hammer at a pedestal and it lights up a column of
    LED panels with 8x8 graphics.

    The one I am repairing was made in 2001 and it is breaking down. The
    surface mounted serial drivers are loosing connection to the PCBs from
    being thermally stressed over a couple of decades of outdoor use and I
    want to make replacement panels (the original company has abandoned the
    product) that will be more durable.

    Currently on the rear (somewhat protected) side of the board is the
    electronics, covered (or course) with a conformal coating. The outer
    side is an 8 X 8 matrix of LEDs in groups of 8 for each pixel of the 64
    pixels on the panel.

    There are 40 - 8 x 8.75 inch panels going up around 30 feet...

    Is there a better way to solder on SMD devices to help avoid thermal
    solder failure? After connection corrosion, the biggest problem is
    solder failure of the SMD pads to the PCBs.

    Thanks!

    John :-#)#

    If the column of lights is attached to the same base as the hammer target, there could be significant solder fatigue from the vibrations traveling up the light column.

    No, the tower is on its own, no risk of shock at least!


    Switching to lead-free will improve fatigue resistance. While there are lead-free alloys specifically designed for good fatigue resistance, and
    any solder mfgr app engineer could make a recommendation, the standard
    SAC305 is a significant improvement over tin-lead according to numerous
    test results published in the industry trade magazines like SMT
    Technology.

    Thanks for that information!


    Stiffening the boards with a thicker material or with stiffeners will
    reduce thermal bowing from sunshine. Leaving all unused area covered with copper ground plane and white or light colored soldermask might help.

    Copper ground plane is planned.


    Flexible mounting to isolate vibration might help, perhaps clamp between silicone foam strips with rubber bushings around the screws or similar,
    could also provide sealing of the back side.

    It is not so much vibration as much as thermal changes over a day in the sun...times many days!


    Flexible conformal coating will prevent the coating from stressing solder,
    as can happen with rigid materials due to differential thermal expansion.

    Conformal coating is part of the problem for repairs. While it is
    flexible it doesn't peel off easily at all - which I guess is the intent
    - but this does make it harder to repair. Are there conformal coating
    that respond well to a solvent that isn't toxic?


    As Buzz mentioned, underfill can help if your assembler has the
    capability.

    I will look into that too.


    Regards,
    Glen

    Thanks for taking the time!

    John :-#)#
    --
    (Please post followups or tech inquiries to the USENET newsgroup)
    John's Jukes Ltd.
    #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
    (604)872-5757 (Pinballs, Jukes, Video Games)
    www.flippers.com
    "Old pinballers never die, they just flip out."

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to John Robertson on Wed Aug 7 23:13:43 2024
    John Robertson <jrr@flippers.com> wrote:
    On 2024-08-06 3:27 p.m., Glen Walpert wrote:
    On Thu, 1 Aug 2024 17:50:29 -0700, John Robertson wrote:

    I have another problem - display panels on an outdoor hammer game - the
    style that you swing a hammer at a pedestal and it lights up a column of >>> LED panels with 8x8 graphics.

    The one I am repairing was made in 2001 and it is breaking down. The
    surface mounted serial drivers are loosing connection to the PCBs from
    being thermally stressed over a couple of decades of outdoor use and I
    want to make replacement panels (the original company has abandoned the
    product) that will be more durable.

    Currently on the rear (somewhat protected) side of the board is the
    electronics, covered (or course) with a conformal coating. The outer
    side is an 8 X 8 matrix of LEDs in groups of 8 for each pixel of the 64
    pixels on the panel.

    There are 40 - 8 x 8.75 inch panels going up around 30 feet...

    Is there a better way to solder on SMD devices to help avoid thermal
    solder failure? After connection corrosion, the biggest problem is
    solder failure of the SMD pads to the PCBs.

    Thanks!

    John :-#)#

    If the column of lights is attached to the same base as the hammer target, >> there could be significant solder fatigue from the vibrations traveling up >> the light column.

    No, the tower is on its own, no risk of shock at least!


    Switching to lead-free will improve fatigue resistance. While there are
    lead-free alloys specifically designed for good fatigue resistance, and
    any solder mfgr app engineer could make a recommendation, the standard
    SAC305 is a significant improvement over tin-lead according to numerous
    test results published in the industry trade magazines like SMT
    Technology.

    Thanks for that information!


    Stiffening the boards with a thicker material or with stiffeners will
    reduce thermal bowing from sunshine. Leaving all unused area covered with >> copper ground plane and white or light colored soldermask might help.

    Copper ground plane is planned.


    Flexible mounting to isolate vibration might help, perhaps clamp between
    silicone foam strips with rubber bushings around the screws or similar,
    could also provide sealing of the back side.

    It is not so much vibration as much as thermal changes over a day in the sun...times many days!


    Flexible conformal coating will prevent the coating from stressing solder, >> as can happen with rigid materials due to differential thermal expansion.

    Conformal coating is part of the problem for repairs. While it is
    flexible it doesn't peel off easily at all - which I guess is the intent
    - but this does make it harder to repair. Are there conformal coating
    that respond well to a solvent that isn't toxic?

    You can solder right through acrylic conformal coating.

    Cheers

    Phil Hobbs


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

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  • From Glen Walpert@21:1/5 to John Robertson on Thu Aug 8 01:14:16 2024
    On Wed, 7 Aug 2024 14:34:14 -0700, John Robertson wrote:

    On 2024-08-06 3:27 p.m., Glen Walpert wrote:
    On Thu, 1 Aug 2024 17:50:29 -0700, John Robertson wrote:

    I have another problem - display panels on an outdoor hammer game -
    the style that you swing a hammer at a pedestal and it lights up a
    column of LED panels with 8x8 graphics.

    The one I am repairing was made in 2001 and it is breaking down. The
    surface mounted serial drivers are loosing connection to the PCBs from
    being thermally stressed over a couple of decades of outdoor use and I
    want to make replacement panels (the original company has abandoned
    the product) that will be more durable.

    Currently on the rear (somewhat protected) side of the board is the
    electronics, covered (or course) with a conformal coating. The outer
    side is an 8 X 8 matrix of LEDs in groups of 8 for each pixel of the
    64 pixels on the panel.

    There are 40 - 8 x 8.75 inch panels going up around 30 feet...

    Is there a better way to solder on SMD devices to help avoid thermal
    solder failure? After connection corrosion, the biggest problem is
    solder failure of the SMD pads to the PCBs.

    Thanks!

    John :-#)#

    If the column of lights is attached to the same base as the hammer
    target,
    there could be significant solder fatigue from the vibrations traveling
    up the light column.

    No, the tower is on its own, no risk of shock at least!


    Switching to lead-free will improve fatigue resistance. While there
    are lead-free alloys specifically designed for good fatigue resistance,
    and any solder mfgr app engineer could make a recommendation, the
    standard SAC305 is a significant improvement over tin-lead according to
    numerous test results published in the industry trade magazines like
    SMT Technology.

    Thanks for that information!


    Stiffening the boards with a thicker material or with stiffeners will
    reduce thermal bowing from sunshine. Leaving all unused area covered
    with copper ground plane and white or light colored soldermask might
    help.

    Copper ground plane is planned.


    Flexible mounting to isolate vibration might help, perhaps clamp
    between silicone foam strips with rubber bushings around the screws or
    similar, could also provide sealing of the back side.

    It is not so much vibration as much as thermal changes over a day in the sun...times many days!

    Board stiffeners to reduce warping, compliant mounting to allow thermal expansion without restraint, and cooling with a fan blowing up the column should all help some with that.

    Flexible conformal coating will prevent the coating from stressing
    solder,
    as can happen with rigid materials due to differential thermal
    expansion.

    Conformal coating is part of the problem for repairs. While it is
    flexible it doesn't peel off easily at all - which I guess is the intent
    - but this does make it harder to repair. Are there conformal coating
    that respond well to a solvent that isn't toxic?

    The non-toxic part is the issue there. Miller-Stephenson sells a
    conformal coat stripper which will remove all coatings except epoxy which
    they claim is environmentally friendly but I haven't used it or read the
    MSDS:

    https://miller-stephenson.com/chemicals/conformal-coating/

    I have used their MS-460H - soft silicone, solder thru (messy), easily
    scraped off. easy poke-through with a sharp probe, as well as the similar Chemtronics Konform SR which strips with xylene or acetone:

    https://www.chemtronics.com/conformal-coating-selection-guide

    As Buzz mentioned, underfill can help if your assembler has the
    capability.

    I will look into that too.

    Underfill is generally epoxy, glues the components to the board, great for shock and vibration but terrible for rework.

    Regards,
    Glen

    Thanks for taking the time!

    John :-#)#

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  • From John Robertson@21:1/5 to Glen Walpert on Thu Aug 8 14:49:34 2024
    On 2024-08-07 6:14 p.m., Glen Walpert wrote:
    On Wed, 7 Aug 2024 14:34:14 -0700, John Robertson wrote:

    On 2024-08-06 3:27 p.m., Glen Walpert wrote:
    On Thu, 1 Aug 2024 17:50:29 -0700, John Robertson wrote:

    I have another problem - display panels on an outdoor hammer game -
    the style that you swing a hammer at a pedestal and it lights up a
    column of LED panels with 8x8 graphics.

    The one I am repairing was made in 2001 and it is breaking down. The
    surface mounted serial drivers are loosing connection to the PCBs from >>>> being thermally stressed over a couple of decades of outdoor use and I >>>> want to make replacement panels (the original company has abandoned
    the product) that will be more durable.

    Currently on the rear (somewhat protected) side of the board is the
    electronics, covered (or course) with a conformal coating. The outer
    side is an 8 X 8 matrix of LEDs in groups of 8 for each pixel of the
    64 pixels on the panel.

    There are 40 - 8 x 8.75 inch panels going up around 30 feet...

    Is there a better way to solder on SMD devices to help avoid thermal
    solder failure? After connection corrosion, the biggest problem is
    solder failure of the SMD pads to the PCBs.

    Thanks!

    John :-#)#

    If the column of lights is attached to the same base as the hammer
    target,
    there could be significant solder fatigue from the vibrations traveling
    up the light column.

    No, the tower is on its own, no risk of shock at least!


    Switching to lead-free will improve fatigue resistance. While there
    are lead-free alloys specifically designed for good fatigue resistance,
    and any solder mfgr app engineer could make a recommendation, the
    standard SAC305 is a significant improvement over tin-lead according to
    numerous test results published in the industry trade magazines like
    SMT Technology.

    Thanks for that information!


    Stiffening the boards with a thicker material or with stiffeners will
    reduce thermal bowing from sunshine. Leaving all unused area covered
    with copper ground plane and white or light colored soldermask might
    help.

    Copper ground plane is planned.


    Flexible mounting to isolate vibration might help, perhaps clamp
    between silicone foam strips with rubber bushings around the screws or
    similar, could also provide sealing of the back side.

    It is not so much vibration as much as thermal changes over a day in the
    sun...times many days!

    Board stiffeners to reduce warping, compliant mounting to allow thermal expansion without restraint, and cooling with a fan blowing up the column should all help some with that.

    Drat, I didn't think of that as a problem. These panels are currently
    screwed (4 screws on each of two sides) to an aluminum column...it makes
    sense that the column expands with temperature changes and if the boards
    are secured tightly (8 screws/panel) then this could be part of the
    issue. Flexible mounting needs looking into!


    Flexible conformal coating will prevent the coating from stressing
    solder,
    as can happen with rigid materials due to differential thermal
    expansion.

    Conformal coating is part of the problem for repairs. While it is
    flexible it doesn't peel off easily at all - which I guess is the intent
    - but this does make it harder to repair. Are there conformal coating
    that respond well to a solvent that isn't toxic?

    The non-toxic part is the issue there. Miller-Stephenson sells a
    conformal coat stripper which will remove all coatings except epoxy which they claim is environmentally friendly but I haven't used it or read the MSDS:

    https://miller-stephenson.com/chemicals/conformal-coating/

    I have used their MS-460H - soft silicone, solder thru (messy), easily scraped off. easy poke-through with a sharp probe, as well as the similar Chemtronics Konform SR which strips with xylene or acetone:

    https://www.chemtronics.com/conformal-coating-selection-guide

    I'll take a look into that.


    As Buzz mentioned, underfill can help if your assembler has the
    capability.

    I will look into that too.

    Underfill is generally epoxy, glues the components to the board, great for shock and vibration but terrible for rework.

    I think with new panels that securing the chips to the board with
    underfill might well be a good idea.


    Regards,
    Glen

    Thanks for taking the time!

    John :-#)#


    Thanks!

    John :-#)#

    --
    (Please post followups or tech inquiries to the USENET newsgroup)
    John's Jukes Ltd.
    #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
    (604)872-5757 (Pinballs, Jukes, Video Games)
    www.flippers.com
    "Old pinballers never die, they just flip out."

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)