PCB's for DIY

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: luketeaford, lisa, Kent, Joe.

Post Reply
MarkLaEl
Learning to Wiggle
Posts: 20
Joined: Sat Apr 05, 2014 10:24 am
Location: Abergavenny,South Wales, UK

PCB's for DIY

Post by MarkLaEl » Tue Jul 16, 2019 1:47 pm

A general request to everyone producing PCB's for DIY use.

I am very much in support of the idea of leaving large copper areas to save on etching etc.; but would it be possible to leave a short track for any GND pad thus mitigating the chance of needing extra heat.


Rant over!

User avatar
CLee
Super Deluxe Wiggler
Posts: 1741
Joined: Mon Apr 05, 2010 6:49 pm
Location: Chicago
Contact:

Post by CLee » Tue Jul 16, 2019 2:37 pm

Don’t most people use thermal relief pads for the ground plane? I know I do and I’d suspect most others too.

You can look, the actual ground pad is connected to the plane by 4 small traces with gaps between them. It reduces the amount of heat drawn away from the pad when soldering.

User avatar
TheMentat
Common Wiggler
Posts: 183
Joined: Thu Nov 30, 2017 1:48 am
Location: Ocean Park

Post by TheMentat » Tue Jul 16, 2019 2:52 pm

CLee wrote:Don’t most people use thermal relief pads for the ground plane? I know I do and I’d suspect most others too.

You can look, the actual ground pad is connected to the plane by 4 small traces with gaps between them. It reduces the amount of heat drawn away from the pad when soldering.
KiCAD seems to default with ground reliefs. I eliminated them on some busboards I built. What a PITA that was to solder! :doh:

User avatar
devinw1
Super Deluxe Wiggler
Posts: 1559
Joined: Tue Aug 07, 2018 11:20 am
Location: Portland, OR
Contact:

Post by devinw1 » Tue Jul 16, 2019 2:57 pm

Thermal reliefs for pads connected to fill zones is pretty standard.

Yeah, not so easy to solder without them, what with having an entire slab of copper soaking up all the heat of the iron.

MarkLaEl
Learning to Wiggle
Posts: 20
Joined: Sat Apr 05, 2014 10:24 am
Location: Abergavenny,South Wales, UK

Post by MarkLaEl » Tue Jul 16, 2019 6:21 pm

Well. I would rather have a GND pad matching all the others, a short track to the GND plane wouldn't make any difference.

User avatar
mskala
Super Deluxe Wiggler
Posts: 2642
Joined: Thu Mar 27, 2014 7:33 am
Location: Toronto
Contact:

Post by mskala » Tue Jul 16, 2019 10:43 pm

MarkLaEl wrote:Well. I would rather have a GND pad matching all the others, a short track to the GND plane wouldn't make any difference.
A "thermal relief pad" isn't really a different pad - it simply is a pad of the same kind as the others, connected to the ground plane by short traces.
North Coast Synthesis Ltd.
Latest Web log posting: Genome Jazz

User avatar
OB1
Common Wiggler
Posts: 185
Joined: Fri Jan 12, 2018 7:11 am
Location: Bristol, UK
Contact:

Post by OB1 » Wed Jul 17, 2019 4:42 am

I've built a ton of DIY modules and I can't recall a PCB that didn't use thermal relief for the GND pads. I'm sure most people do this already.

MarkLaEl
Learning to Wiggle
Posts: 20
Joined: Sat Apr 05, 2014 10:24 am
Location: Abergavenny,South Wales, UK

Post by MarkLaEl » Wed Jul 17, 2019 7:37 am

I can identify thermal pads when I solder a board, what I am suggesting is that where a component or a wire is grounded, it is soldered to a normal pad that links to a GND plane via a short track. I shouldn't have to increase the temperature of the iron for those affected solder points. I wonder if the fact that the GND pads have four little links, the GND plane is still acting as a heatsink therefore creating an imbalance to the component's other leg.

User avatar
mskala
Super Deluxe Wiggler
Posts: 2642
Joined: Thu Mar 27, 2014 7:33 am
Location: Toronto
Contact:

Post by mskala » Wed Jul 17, 2019 7:52 am

MarkLaEl wrote:I can identify thermal pads when I solder a board, what I am suggesting is that where a component or a wire is grounded, it is soldered to a normal pad that links to a GND plane via a short track.
Maybe it would help if you could post a picture of what you have in mind, because the difference between that and a thermal relief isn't coming through from this text description.
North Coast Synthesis Ltd.
Latest Web log posting: Genome Jazz

ricko
Wiggling with Experience
Posts: 338
Joined: Sat Dec 03, 2016 5:36 am
Location: Sydney, Australia
Contact:

Post by ricko » Wed Jul 17, 2019 8:20 am

I understand this request.

I dont mind a little thermal variability between pads, but I certain have found myself having to up the soldering iron heat to get any take-up of solder on grounded pads, on some bought boards by solid engineers. It is a recipe for dry joints. And it is not just boards with a ground plane...

The Wiggler who said he has never seen it is lucky. (Now I need to go and check my boards to see if Kicad did the right thing: I dont use filled ground planes exactly to avoid any soldering issues, though I do specify wider traces and separation for power and ground on boards, and more-than-default separation of signal traces in any case.)

I guess one thing I dont have clear in my mind is why you would have a filled ground plane rather than just bigger traces forming more of a star to the power caps, on an all-analog audio-rate board with no need for concern about radio interference. For audio-rate only-analog processing, isnt a star-ground topologi on the PCB preferable to a ground plane (or is the best to have both?) Modular signals seem too hot for external radio interfence to be a problem (and cables would be affected worse, yes?) And if crosstalk is the problem, why isn't using wider trace separation (and a star rather than bus topologi for ground) a better solution than a ground plane? (Not a rhetorical question, a real one.)

(If you have some digital ICs or high speed signals, then I can see it is a different set of tradeoffs.)

MarkLaEl
Learning to Wiggle
Posts: 20
Joined: Sat Apr 05, 2014 10:24 am
Location: Abergavenny,South Wales, UK

Post by MarkLaEl » Wed Jul 17, 2019 12:03 pm

TheMentat and Ricko,

You both understand what I mean.

If you take a PCB with no GND plane, then a GND pad would reach the 'earth' point via a track, picking up other GND pads along the way.

If a GND plane is introduced, then leave a partial 'Ox-Bow Lake' at every GND pad.

I.E. The 'water' is the etched PCB and the 'land is the GND pad :|

Therefore the heat transfer remains the same.

Post Reply

Return to “Music Tech DIY”