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Double Check my PCB for me please!

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coillah

Sun Jan 11 2009, 08:54PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Here's the new ground plane and overall:

Marko

Sun Jan 11 2009, 11:25PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Well, if you really want a double sided board and a groundplane, you could really make the groundplane completely unbroken and put most of your traces on the top of your board, only tracing the bottom side where you need to jumper the top side or have to connect a component that can't be soldered from top.

In case of double sided boards, it can also be proffered to set up a plane (or several planes) on top, and connecting them either to GND, or supply voltages. They help saving the etchant and equalizing the etching time.

The other thing is, that for such a simple board, and especially since it's your first one, I absolutely don't see any need for a double sided board. You're going to have hard time aligning your top and bottom side, and for your first board, rather think about how to fit it into a metal case if shielding is necessary.
Before etching the board, measure your box and mounts, then place mounting holes on the board accordingly!

It's the same for commercial boards, but for homemaking I prefer single side whenever possible.

Don't be afraid to use a few jumpers where required, keep high frequency connections short and put decoupling capacitors close to IC's.

PS. why did you put resistors between unused 74hc14 inputs and Ucc? Just connect them directly to Ucc or ground, whichever handy.

Marko

coillah

Sun Jan 11 2009, 11:51PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

I read online that they should be tied through resistors (the inverter gates).

I am going to attempt the double sided PCB. Despite how completely unnecessary it may be. Woo! Ill report back with the gruesome details.

Plus, how cool would it be if I pulled it off and made a really nice double sided PCB. You guys would all be hella jealous...

probably not though, you'd just think I was dumb for doing it the long way. hahahahahaha

later!

cjk2

Mon Jan 12 2009, 04:39AM

Registered Member #51 Joined: Thu Feb 09 2006, 04:17AM
Location:
Posts: 263

You do not need resistors on the inverter's gates. Disable both ucc's with the interrupter, not just one. How are you going to solder the pots? I have a hard time soldering without thermals...

coillah

Mon Jan 12 2009, 06:07AM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

>_< I totally missed the interrupter trace.

Oh well, I am still perfecting the art of magazine paper pattern transfer, so I can add that trace in later.

Thermals?

Myke

Mon Jan 12 2009, 06:24AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Terminals... Why would the pot not have terminals? The pots are fine.

EDIT: Ah, thanks for the explanation.

Herr Zapp

Mon Jan 12 2009, 06:20PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

coillah, Myke -

cjk2 wrote: "I have a hard time soldering without thermals..."

He was talking about therrmally isolated solder pads, not potentiometer terminals. If you place a component pad (either a through-hole, or a pad for a surface-mount device) in a large area of copper (e.g. the ground plane, or other wide trace) it will be very difficult to solder the part, because the large area of copper will create a heat-sink that makes it very difficult to get the copper hot enough to allow the solder to flow properly at the component lead. So, unless the particular part is carrying high current, thermally "isolate" the pad from the surrounding large area of copper by etching copper away from the perimeter of the pad, leaving only a few narrow "spokes" to connect the pad to the surrounding larger copper area. This provides thermal isolation, but electrical continuity.

Not using thermal isolation pads is one of the biggest causes of cold solder joints on "home-made" PCBAs.

Thermal isolation pads are also called "thermal ties". Here's a link to a brief write-up describing thermal ties and how they're designed. At the end is a very useful chart showing trace resistance as a function of trace width and copper thickness:

Regards,
Herr Zapp

coillah

Mon Jan 12 2009, 08:04PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

ah ha! I remember soldering a ramsey kit a little bit ago, and that thing had no thermal pads, and it was a BEAST to solder...

very interesting.

coillah

Wed Mar 11 2009, 07:06AM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Hey guys,

got a new pcb layout. Could you take a quick look and tell me what you think?

coillah

Wed Mar 11 2009, 07:09AM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

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