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Old 6th April 2009, 08:22 PM   #1
Electrons are yellow and more is better!
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Default Diamond Buffer - Super Buffer

What do you think of my latest work?, 4-layer, gold pads

Size = 21.7 x 32.0 mm, 0.852 x 1.261 in.

Schematic

BOM
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File Type: jpg ssb01r0_overview.jpg (45.9 KB, 2134 views)
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Old 6th April 2009, 08:54 PM   #2
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You sink some current from the input signal node ??
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Old 6th April 2009, 08:59 PM   #3
Electrons are yellow and more is better!
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This is for class A biasing of the opamp.
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Old 6th April 2009, 09:09 PM   #4
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Looks Ok to me, why gold? (except of another gold thing on the photo implying you're married)
Any special adhesive to solder properties?
I see you like to have components dense on both sides
If I were you I'd add another via on the other edge of the PCB to connect all the ground planes.
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Old 6th April 2009, 09:19 PM   #5
Electrons are yellow and more is better!
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Gold looks nice, don't you think?

I could add a couple of vias but the pcb is really small and no current flows in the groundplane
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Old 6th April 2009, 09:46 PM   #6
AKSA is offline AKSA  Australia
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PA,

Very nice work, beautiful board, nicely designed circuit.

How does it sound? Clean, smooth, IM free? What is the distortion profile?

Hugh
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Old 6th April 2009, 09:59 PM   #7
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Hi P-A,

Those are very nice looking boards. Care is required with gold and soldering though. Check out this PDF file relating to gold embrittlement of solder joints.
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Old 6th April 2009, 10:35 PM   #8
AKSA is offline AKSA  Australia
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Thanks Andy,

This is sufficient evidence for me to move away from Au electroplated boards. It is clear that gold embrittlement causes reliability problems, even at very thin plating levels.

Hugh
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Old 6th April 2009, 10:44 PM   #9
andy_c is offline andy_c  United States
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Hi Hugh,

I'm not a mechanical guy, so I'm certainly no expert on this. But I used to work in the aerospace industry, and I remember the problem from there. Back when they were using discrete, leaded components, all components with gold-plated leads had their leads dipped in a solder pot before being installed on the boards. I'm not sure why this helped, but that's what they did.
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Old 6th April 2009, 10:53 PM   #10
AKSA is offline AKSA  Australia
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Andy,

I'd guess it's a phase change issue, which is related to how quickly the solder cools. Dipped into a solder pot, the temperatures are more uniform through the lead, and will thus cool slower on withdrawal, and this could reduce the embrittlement at subsequent installation because the operation would then be much quicker since it's already tinned.

Those microphotos were alarming, with shear lines like a broken ice sheet. No wonder the SMDs literally fell off the board.

Hugh
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