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Subject: Re: What are these terms in PCB design?
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Thu, 03 Oct 2002 19:29:33 GMT
NNTP-Posting-Date: Thu, 03 Oct 2002 21:29:33 MET DST
"Spehro Pefhany" schrieb im Newsbeitrag
> The renowned The little lost angel
> > Top layer, bottom layer... which's the side the solder's on? I think
> > it's the bottom layer. So if I am making a one layer PCB, I should put
> > my traces and pads on the bottom and the PCB makers will know which
> > way it should face?
> Ah, well, traditionally I think single-sided boards have been laid out as
> if you are looking at the bottom of the board, and all others have been
> laid out as if you are looking at the top (the side opposite the solder).
> I think today, it probably has switched to laying the board out looking at
> the component side even for single sided boards. In any case, I'd call the
> part with the traces the "bottom", whether it was laid out reversed or
> not, so your file with the traces should be named appropriately or
> referenced in your readme file.
> DON'T depend on the name alone. Put some text on the board that is
> "right-reading", so they can flip the layer if required to get it right.
> It can be a PITA to have to put parts in the wrong side (made that mistake
> ONCE on a prototype single-sided board). ;-)
> > Plus, the PCB programs have this thing call pour/fill, is this what I
> > use if I want to fill up an entire empty area with copper to act as a
> > heatsink for a LED that's connected immediately to that trace?
> Yup. But make sure your program uses "thermals" to make the soldering
> easier (the good ones do, and automatically).
> Best regards,
> Spehro Pefhany
Well, inside the LED there are two leads, one (the negative) is directly
connected to the little metal reflector where the die is soldered to,
whereas the other is bonded with a tiny wire to the top of the die. So I
think the best effect is to leave the cathode lead at full length and solder
a copper sheet (cut from foil) to it and have it perpendicular to the board.
If the circuit allows it this should be also the gnd. Use some low melting
point solder to not overheat the semiconductor.
If you use thermals here the theta goes way up.
To pour the copper, use the polygon command and name it the cathode node
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