Diamond Buffer - Super Buffer

peranders · 6th April 2009, 09:22 PM

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

darkfenriz · 6th April 2009, 09:54 PM

You sink some current from the input signal node ??

peranders · 6th April 2009, 09:59 PM

This is for class A biasing of the opamp.

darkfenriz · 6th April 2009, 10:09 PM

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.

peranders · 6th April 2009, 10:19 PM

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

AKSA · 6th April 2009, 10:46 PM

PA,

Very nice work, beautiful board, nicely designed circuit.

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

Hugh

andy_c · 6th April 2009, 10:59 PM

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.

AKSA · 6th April 2009, 11:35 PM

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

andy_c · 6th April 2009, 11:44 PM

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.

AKSA · 6th April 2009, 11:53 PM

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

6th April 2009, 09:59 PM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	This is for class A biasing of the opamp. __________________ /Per-Anders (my first name) or P-A as my friends call me

6th April 2009, 10:19 PM	#5
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	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 __________________ /Per-Anders (my first name) or P-A as my friends call me

6th April 2009, 10:46 PM	#6
AKSA diyAudio Member Join Date: Sep 2001 Location: Melbourne, Australia	PA, Very nice work, beautiful board, nicely designed circuit. How does it sound? Clean, smooth, IM free? What is the distortion profile? Hugh __________________ Aspen Amplifiers P/L (Australia) www.aksaonline.com

6th April 2009, 11:35 PM	#8
AKSA diyAudio Member Join Date: Sep 2001 Location: Melbourne, Australia	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 __________________ Aspen Amplifiers P/L (Australia) www.aksaonline.com

6th April 2009, 11:53 PM	#10
AKSA diyAudio Member Join Date: Sep 2001 Location: Melbourne, Australia	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 __________________ Aspen Amplifiers P/L (Australia) www.aksaonline.com


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6th April 2009, 09:54 PM	#2
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	You sink some current from the input signal node ??

6th April 2009, 10:09 PM	#4
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	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.

6th April 2009, 10:59 PM	#7
andy_c Banned Join Date: Apr 2003	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.

6th April 2009, 11:44 PM	#9
andy_c Banned Join Date: Apr 2003	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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