...All Things Vero...

Would you consider buying a VERO after reading through some of the posts?

  • Total voters
    357
guod

guod

Well-Known Member
reichelt.de
TG-WLPK-001 :: Kryonaut thermal paste 1 g/0.27 ml :: 5.49€
TG-WLPK-015 :: Kryonaut Thermal Compound 5.55g/1.5ml :: 15.95€
TG-WLPK-030 :: Kryonaut Wärmeleitpaste 11,1 g / 3 ml :: 25.11€

6 cent more
reichelt.at
TG-WLPK-001 :: Kryonaut thermal paste 1 g/0.27 ml :: 5.54€
TG-WLPK-015 :: Kryonaut Thermal Compound 5.55g/1.5ml :: 16.08



 
captainmorgan

captainmorgan

Well-Known Member
Guess I must have fallen for some biased testing from the marketing department. It's been at least 6 or 7 years since I did any serious CPU OCing. I did manage to OC a AMD CPU from 1.9 to over 3.1 on air cooling back in the day.
 
stardustsailor

stardustsailor

Well-Known Member
Personally ,with the experience I've gained so far while making LED grow lights ,
when it comes to Thermal Interface Materials ,the first of all the rest characteristic I look for is how easy it is
to apply the TIM in a really thin layer ( 1/10 of millimeter= 100 microns ,being the thickest layer for my standards).
I do not pay so much attention to the thermal conductivity or any other characteristic,as to the "ease of application ".

For example :

Equation : Thermal resistance of an interface material
Rθ TIM = t / (k* A)
Where:
t is the thermal interface material bond line thickness (BLT) (m)
k is the thermal conductivity (W/m-K)
A is the heat source contact area (m2)

A for Vero 29 LED COB arrays = ~ 0.001 m^2 ( 31.8 mm x 31.8 mm )

Paste "X" is really easy to apply into a layer of 50 microns ( 0,00005 m ) and has a thermal
conductivity of 5 W/m-K

Paste " Z " is really a PITA to apply into a layer of 150 microns ( 0,00015 m ) and has a
a thermal conductivity of 15 W/m-K (!!!)


Rth X = 0.01 °C/W
Rth Z = 0.01 °C/W

Paste X has the same thermal resistance of paste Z ,because it can be applied into a layer of 1/3 of thickness than the Z paste layer.Although paste Z has 3x times higher thermal conductivity,than paste X has . ...

But then ,WTF do I know ?
That's only my POV ...

Still ,my favourite TIM remains Arctic Silver 5 ....
The only paste I've tested and used ,that can be applied into a really thin -thinner than thinnest -
layer ...
Only downside so far ,is that it needs about 200 hours ( approx 10 days ) of curing before COBs will be "put on duty " ...


Cheers.
:peace:
 
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stardustsailor

stardustsailor

Well-Known Member
stardustsailor

stardustsailor

Well-Known Member
guod said:
50% helps alot when you mount your cobs with Kapton-tape ;)
Click to expand...
" Contact resistance " is the key ...;)

Or also known as
" AN : How to make a highly thermal conductive paste ,behave worse than the worst toothpaste,
by using Kapton tape "

Cheers,brother.
:clap:

P.S.
Many-many Thanx to you ,for the LM2907 advice .
You saved my day ,once again.
( Can you believe that the ICs I've found were made from National Semiconductor ?
Yes...That old ... )
 
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stardustsailor

stardustsailor

Well-Known Member
GFS_Nic said:
Hello,

What does that mean ? We should run it at the lowest power for 10 days before run it at full power ?
Thank you for sharing all the informations and datas, your point of view is always interesting.

Peace
Click to expand...
It means you should wait for 8-10 days before switching ON the LEDS/ COBs for more than 10-15 minutes ...
Even at lowest power possible ...

Let it cure first ...
 
robincnn

robincnn

Well-Known Member
stardustsailor said:
It means you should wait for 8-10 days before switching ON the LEDS/ COBs for more than 10-15 minutes ...
Even at lowest power possible ...

Let it cure first ...
Click to expand...
Artic silver says - This break-in will occur during the normal use of the computer as long as
the computer is turned off from time to time and the interface is allowed to cool.

May be letting it sit 10 days idle would be better.

Break-In Period Explained: ( from artic silver website)
Due to the unique carrier fluid used and the shapes and sizes of the thermally
conductive particles in Arctic Silver's thermal compounds it will take multiple
thermal cycles to achieve maximum particle to particle thermal conduction and
for the heatsink to metal cap interface to reach maximum conductivity. (This
period will be longer in a system without a fan on the heatsink.) On systems
measuring actual internal core temperatures via the CPU's internal diode, the
measured temperature will often drop slightly to significantly over this "break-in"
period. This break-in will occur during the normal use of the computer as long as
the computer is turned off from time to time and the interface is allowed to cool.
Arctic Silver 5:
Break-in period: 200 hours (Break-in period will occur during normal use.)
Temps will drop several degrees over the break-in period measured with a thermal
diode in the hottest part of the CPU core.
 
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stardustsailor

stardustsailor

Well-Known Member
robincnn said:
This break-in will occur during the normal use of the computer as long as
the computer is turned off from time to time and the interface is allowed to cool. Might be better if you dont use them for 10 days.

Break-In Period Explained: ( from artic silver website)
Due to the unique carrier fluid used and the shapes and sizes of the thermally
conductive particles in Arctic Silver's thermal compounds it will take multiple
thermal cycles to achieve maximum particle to particle thermal conduction and
for the heatsink to metal cap interface to reach maximum conductivity. (This
period will be longer in a system without a fan on the heatsink.) On systems
measuring actual internal core temperatures via the CPU's internal diode, the
measured temperature will often drop slightly to significantly over this "break-in"
period. This break-in will occur during the normal use of the computer as long as
the computer is turned off from time to time and the interface is allowed to cool.
Arctic Silver 5:
Break-in period: 200 hours (Break-in period will occur during normal use.)
Temps will drop several degrees over the break-in period measured with a thermal
diode in the hottest part of the CPU core.
Click to expand...
Yes ,correct ...
Still due to the fact that Arctic Silver 5 has a non-silicon carrier ,and from what I've noticed it is of an
evaporative nature (paste eventually turns into solid film ),I tend to let it cure ,without any thermal load.
Applying thermal load may cause sudden "bulk evaporation" ,which in turn may cause "gaps" or "voids"
in the TIM layer ,which is still in " liquid " form. Do not forget that CPUs are way different from LED COBs,regarding heat output ... A CPU will never or seldom output the same amount of heat over a period of time,
while COBs when they reach their thermal equilibrium will output the same amount of heat over a period of time .
My policy tends to be " No risks taken ,for no reason " .
After ten days of curing ,the thermal paste is dry enough ,and no sudden "bulk evaporation" will occur ..
(Thus the gases will try to find a way to exaust , forming gaps or voids in the TIM layer ) ...
More than that ,due to the unknown nature of the vapours / volatile gases from carrier ( most probably an organic compound aka VOC ) ,it remains unknown the effect that those gases will have on the LES of the COB(s).
So once again ,I insist on that one ...Let it cure first .
It's only 8-10 days ,worth of waitin' ...

Cheers.
:peace:
 
stardustsailor

stardustsailor

Well-Known Member
The most important aspect regarding TIM ( thermal paste ) is the contact pressure ,
between the two surfaces that the TIM is "sandwiched" into .

AN30 of Bridgelux ( " Thermal Management for Bridgelux Vero Series LED Arrays " ),
provides enough information .

(...) There are 3 resistances in the TIM, the resistance through the TIM material and the contact resistance (remaining air layers) between the TIM surface and array and between the TIM surface and heat sink. The contact resistances dominate when the TIM does not fill in the voids such as with at thermal pad. A thermal grease or phase change material will generally fill more of the voids and have a thin bond line, thus, the contact resistance is less and the material resistance will dominate. (..)

So...
In order to decrease contact resistances ,contact pressure should increase ..

On another application note we can read :
AN31 ( Handling and Assembly of Bridgelux Vero Series LED Arrays )

(...)
Screw Head Type
Bridgelux recommends using screws with a flat shoulder for mounting Vero LED modules, see figure 17 below. A wide variety of commercially available screws types can be used to meet design requirements. Examples include pan head, button head, round head, and truss head screws. Flat head and oval head screws or other screws with an angled surface should not be used.When selecting a screw, consider screws that have a low profile screw head. A low profile screw head has the advantage of blocking less of the light emitted from the Vero LED module. Additionally, if a secondary optic is to be used in the application, a low profile screw head allows more room for the optical components.
Screw Torque
It is critical to ensure the proper torque is applied to the fasteners when mounting the Vero LED module to a heat sink. If too little torque is applied, the thermal path between the Vero LED module and the heat sink will be compromised while excessive torque may result in damage to the Vero LED module housing**. Many variables affect the actual torque required to seat the screw such as thread friction, materials of the heat sink and screw, screw head friction, etc. For example, a machine screw with typical thread friction can be seated with < 1 lbf-in of torque, but it may take much higher torque to seat a thread forming screw. Table 5 below lists the suggested torque values based on the screw size shown and typical friction factors. It is the responsibility of the customer to test and ensure the correct torque values are specified and used during the assembly process.
Note that the holder of the Vero LED module is constructed from a plastic material and is engineered to flex so that the bottom of the plastic will contact the heat sink surface, see figure 18.
Flat Washers, Lock Washers, Self-Locking Fasteners, and Thread Sealants
**Flat washers may be used to protect the Vero LED module from damage resulting from excess torque and to provide a wider distribution of the force applied by the screw. Flat washers, however, do not prevent fasteners from loosening in vibration environments. To prevent loosening of screws during vibration or thermal cycling Bridgelux recommends using lock washers, self-locking fasteners, or thread locking sealants. (...)


A small "equation" of success :

Flat shoulder screws + washers +second- larger in diameter -washers +thread lock compound + enough torque + extra thin layer of thermal paste = Best COB assembly possible & best heat transfer from COBs' case to the heat sink,without risking damaging the COB.

Cheers.
:peace:
 
CanadianONE

CanadianONE

Well-Known Member
stardustsailor said:
The most important aspect regarding TIM ( thermal paste ) is the contact pressure ,
between the two surfaces that the TIM is "sandwiched" into .

AN30 of Bridgelux ( " Thermal Management for Bridgelux Vero Series LED Arrays " ),
provides enough information .

(...) There are 3 resistances in the TIM, the resistance through the TIM material and the contact resistance (remaining air layers) between the TIM surface and array and between the TIM surface and heat sink. The contact resistances dominate when the TIM does not fill in the voids such as with at thermal pad. A thermal grease or phase change material will generally fill more of the voids and have a thin bond line, thus, the contact resistance is less and the material resistance will dominate. (..)

So...
In order to decrease contact resistances ,contact pressure should increase ..

On another application note we can read :
AN31 ( Handling and Assembly of Bridgelux Vero Series LED Arrays )

(...)
Screw Head Type
Bridgelux recommends using screws with a flat shoulder for mounting Vero LED modules, see figure 17 below. A wide variety of commercially available screws types can be used to meet design requirements. Examples include pan head, button head, round head, and truss head screws. Flat head and oval head screws or other screws with an angled surface should not be used.When selecting a screw, consider screws that have a low profile screw head. A low profile screw head has the advantage of blocking less of the light emitted from the Vero LED module. Additionally, if a secondary optic is to be used in the application, a low profile screw head allows more room for the optical components.
Screw Torque
It is critical to ensure the proper torque is applied to the fasteners when mounting the Vero LED module to a heat sink. If too little torque is applied, the thermal path between the Vero LED module and the heat sink will be compromised while excessive torque may result in damage to the Vero LED module housing**. Many variables affect the actual torque required to seat the screw such as thread friction, materials of the heat sink and screw, screw head friction, etc. For example, a machine screw with typical thread friction can be seated with < 1 lbf-in of torque, but it may take much higher torque to seat a thread forming screw. Table 5 below lists the suggested torque values based on the screw size shown and typical friction factors. It is the responsibility of the customer to test and ensure the correct torque values are specified and used during the assembly process.
Note that the holder of the Vero LED module is constructed from a plastic material and is engineered to flex so that the bottom of the plastic will contact the heat sink surface, see figure 18.
Flat Washers, Lock Washers, Self-Locking Fasteners, and Thread Sealants
**Flat washers may be used to protect the Vero LED module from damage resulting from excess torque and to provide a wider distribution of the force applied by the screw. Flat washers, however, do not prevent fasteners from loosening in vibration environments. To prevent loosening of screws during vibration or thermal cycling Bridgelux recommends using lock washers, self-locking fasteners, or thread locking sealants. (...)


A small "equation" of success :

Flat shoulder screws + washers +second- larger in diameter -washers +thread lock compound + enough torque + extra thin layer of thermal paste = Best COB assembly possible & best heat transfer from COBs' case to the heat sink,without risking damaging the COB.

Cheers.
:peace:
Click to expand...
When applying the thermal compound do you spread the thinnest layer possible over the entire surface of the cob then install or use a different method. Seen many different methods used for CPU's but what is best for our application?
 
stardustsailor

stardustsailor

Well-Known Member
CanadianONE said:
When applying the thermal compound do you spread the thinnest layer possible over the entire surface of the cob then install or use a different method. Seen many different methods used for CPU's but what is best for our application?
Click to expand...
-You will need piece of an old (expired of course ) credit card ...
-....or -better yet- an old-fashioned razor ..(be careful though, with that kind of " tool " ...)
filepicker_dx88U9QfSSqEqRH1MKzA_razorblade.jpg

-Apply several small to tiny blobs of paste all over the thermal pad of the COB .
- Spread the blobs with the piece of the credit card / razor .
-Spread into all directions until a super thin layer is achieved ,covering the whole surface of the thermal pad.
- Use the piece of card /razor to collect any excessive paste and discard it .
( "Shave off " the excess paste )
-Place the COB onto the heat sink .
-Fasten the screws.
-You're done .

Cheers.
 
CanadianONE

CanadianONE

Well-Known Member
stardustsailor said:
-You will need piece of an old (expired of course ) credit card ...
-....or -better yet- an old-fashioned razor ..(be careful though, with that kind of " tool " ...)
View attachment 3474805

-Apply several small to tiny blobs of paste all over the thermal pad of the COB .
- Spread the blobs with the piece of the credit card / razor .
-Spread into all directions until a super thin layer is achieved ,covering the whole surface of the thermal pad.
- Use the piece of card /razor to collect any excessive paste and discard it .
( "Shave off " the excess paste )
-Place the COB onto the heat sink .
-Fasten the screws.
-You're done .

Cheers.
Click to expand...
Thank you for the great explanation. Now to wait to get some cob holders. I initially was going to use the kapton tape method but it will look much better with holders in the end and also put my mind at ease a little. Don't want to always worry about a COB falling off heat sink.
 
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