Thermal pads

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abacom
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Thermal pads

Beitrag von abacom » Donnerstag 25. September 2008, 14:01

p.erasmus



Anmeldungsdatum: 15.01.2007
Beiträge: 85

Verfasst am: 06.02.2007 23:11 Titel: Thermal pads

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Hello

I am a bit confused with the use of the thermal pads
(1) is the easy solder the only reason or benifit if we use then in staed of the old tradisional pads??
(2) I possibly use them incorect however if I have the ground plane switch on in a layer and place 2 thermal pads and then do an electrical test they both light up showing connection in this case I assume it is short circuit what am I doing wrong?
Thank for the help
_________________
P.Erasmus
Automotive Engineering
http://www.wenko.ch
Switzerland

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abacom
Site Admin


Anmeldungsdatum: 30.06.2006
Beiträge: 898

Verfasst am: 07.02.2007 12:34 Titel:

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Hello,

(1)
the thermal-pads are used for an easier soldering. In case of normal pads, you need to have more heat for a longer time, because the full copper around needs to heat up too. This may be a problem, if the soldering is produced with a solder-bath.

(2)
If you place a thermal-pad on the automatic ground-plane, it will be of course connected with this plane (with his 4 little tracks). So, all thermal-pads on the ground plane will be connected. The electrical behaviour of a thermal-pad is exactly the same, as if you use normal pads.

ABACOM support

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p.erasmus



Anmeldungsdatum: 15.01.2007
Beiträge: 85

Verfasst am: 07.02.2007 12:44 Titel:

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Dear ABACOM
yes I agree that they behave as a normal pad however the normal pads do not connect electrically to the ground plane with me the thermal pad connects to the ground plane and causes a short circuit between the pad and the ground plane
or do I misunderstand this.
best regards
_________________
P.Erasmus
Automotive Engineering
http://www.wenko.ch
Switzerland

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abacom
Site Admin


Anmeldungsdatum: 30.06.2006
Beiträge: 898

Verfasst am: 07.02.2007 13:35 Titel:

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Hello,

the normal pads don't connect to the ground-plane, if they have set a distance from the ground-plane (e.g. 0,4 mm). If you select a normal pad, und set this value to "0" (in the statusbar at the bottom), then it will connect to the ground-plane too. A thermal pad is ALWAYS connected to the ground-plane.

ABACOM support.

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p.erasmus



Anmeldungsdatum: 15.01.2007
Beiträge: 85

Verfasst am: 07.02.2007 14:08 Titel:

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I have a normal pad and a thermal pad on the ground plane with the distance set at 0.4; 0.5 and 0.6 and in all thre cases the thermal pad shows short circuit and the normal pad not
Thanks for your timeABACOM
yes the normal pads dont connect to the ground plane I understand your post now i.a.w thermal pads are allways connected to the ground plane and the reason therefore ??
_________________
P.Erasmus
Automotive Engineering
http://www.wenko.ch
Switzerland

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abacom
Site Admin


Anmeldungsdatum: 30.06.2006
Beiträge: 898

Verfasst am: 07.02.2007 14:33 Titel:

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Hello,

thermal pads are used instead of normal pads, because of the better solder-behaviour. A thermal-pad without connection to the ground-plane makes absolutely no sense. In this case you have to use a normal pad.

ABACOM support

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p.erasmus



Anmeldungsdatum: 15.01.2007
Beiträge: 85

Verfasst am: 07.02.2007 23:38 Titel:

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Hello
I am sorry that I have such hard time to understand the use of the thermal pads
I admit that I do understand that the easy solder is a benifit however what is not clear to me is the connection to the ground plane ?

suppose I place 2 thermal pads on the pcb with a ground plane and between the 2 pads I place a resistor as component now the 2 pads are connected to the ground plane and the ground plane now short circuit the resistor so the resistor has no effect no ??
this if I use thermal pads to have better solder possibilities then I can not use the ground plane to help with noise reduction.
again I am sorry not understanding this and I would like to understand it and possibly use sprint to produce a better pcb on the next project.
Thank you for your time and help so far
Peter
_________________
P.Erasmus
Automotive Engineering
http://www.wenko.ch
Switzerland

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abacom
Site Admin


Anmeldungsdatum: 30.06.2006
Beiträge: 898

Verfasst am: 08.02.2007 11:07 Titel:

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Hello Peter,

if you place a normal pad near to a thermal-pad it may happen, that the little tracks of the thermal-pad touches the normal pad and connect these pad to the ground plane.

To avoid these, please use the latest update for Sprint-Layout 5.0.
With this update you can now edit (set or delete) the single tracks of a thermal-pad.

ABACOM support

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p.erasmus



Anmeldungsdatum: 15.01.2007
Beiträge: 85

Verfasst am: 08.02.2007 19:35 Titel:

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Dear ABACOM
I installed the update thank you
I guess I will stay with the normal pads in my PCB`s
for the last couple of years I used them with out any problems and the however the thermal pads is a nice to have
best regards
Peter
_________________
P.Erasmus
Automotive Engineering
http://www.wenko.ch
Switzerland
ABACOM support

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