John,

This was found by searching the archives at http://www.metallography.com/bboard/search.html: 

I have just copied and pasted.  I make no claim as to suitability, etc.

Looks like everyone is playing with nitric and hydrochloric - play carefully


Steve Creswick
Sr Associate - Balanced Enterprise Solutions
http://www.linkedin.com/in/stevencreswick
                         616 834 1883



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The "Metals Handbook Ninth Edition, Volume 9, Metallography and Microstructures", published by the American Society for Metals (ASM International) in 1985, ISBN 0-87170-007-7, has some information about similar alloys beginning on page 452. An example micrograph is shown which was etched with 2 mL HCL, 5mL HNO3, 93 mL methanol. There is more information regarding preparation techniques for tin and it's alloys beginning on page 449 of the same book. 

I would reduce etching time to several seconds.

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Also found were - 

We've etched Pb free solders with Ag content ranging from 1.2% to 3.9% using 108 ml 1.0N HCl and 15 ml HNO3.

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I used nital 2mlHNO3 98mlEthanol to etch my sample 95.5Sn3.9Ag0.6Cu but without obvious effect.First I immerse my sample in ethcant for 3 seconds without obvious effect. Then I eched for another 10 seconds still not work. Then I echted for another 1 min and the microstructue still could not be revealed. Finally I etched my sample in 2mlHCL 6mlHNO3 92mlH2O for 30 seconds this time my sample is severely etched. Could you tell me how to etch lead free solder joint and how long I should use. Thank you very much for your help.

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And,

We have attempted similar results on solder bumps to reveal microstructural features. Try 10% HCI + 90% Methanol for a few seconds or 4 parts Glycerol + 1 part Acetic acid + 1 part HNO3 @80C.










-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Thursday, March 21, 2013 10:53 AM
To: [log in to unmask]
Subject: [TN] SAC 305 etch

What would a good etch be for etching SAC305 solder joints to enhance viewing grain boundaries?

Thanks,
John

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