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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


2% silver solder paste

Rob Palson

#11988

2% silver solder paste | 13 April, 1999

We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated.

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#11989

Re: 2% silver solder paste | 13 April, 1999

| We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated. | Rob: Several points:

1 We used 2% Ag solder on HASL boards for years with no known problems. 2 Ag can improve solder flow across solderable surfaces. 3 If you have too much Ag in your solder joints, you can get into real trouble with brittle and weak Ag3Sn intermetallic compounds. Components can literally fall off boards, as a result of this IM. 4 It seems that Jennie Hwang wrote an article on 2% in "SMT" magazine not too long ago.

On your using 2%:

1 I've never heard that 2% has a positive impact on Au plated boards. What is the basis for your approach? 2 I am not aware of "gold scavaging" or how how Ag would prevent it. What's the background on this? 3 I am painfully aware that Au plating thickness affects solder connections. (Others have posted several threads on SMTnet.)

TTYL

Dave F

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Christopher Lampron

#11990

Re: 2% silver solder paste | 13 April, 1999

| We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated.

Rob,

I currently use a SN 62 2% silver alloy on some of my flex assemblies. This alloy came into use when I had to place some components that have an exotic plating. I was having an incredible problem with tombstoning. The slightly lower reflow temperature of the Silver paste seemed to do the trick. I have no process problems associated with this material and no mechanical or electrical problems.

Hope this helps.

Christopher J. Lampron

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Terry Keen

#11991

Re: 2% silver solder paste | 15 April, 1999

| We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated. | Rob We have been using Sn62Pb36Ag on HASL SnPb for six months with no apparent problems

Terry

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Terry Keen

#11992

Re: 2% silver solder paste | 15 April, 1999

| | We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated. | | | Rob | We have been using Sn62Pb36Ag on HASL SnPb for six months with no apparent problems | | Terry | | That should have beem Sn62/Pb36/Ag2. Finger problems!!

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Vic Lau

#11993

Re: 2% silver solder paste | 16 April, 1999

| | We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated. | |

In general, 2% Ag solder paste will result a stronger solder joint after reflow. The mechancial strength data can be obatined from most of the soldering text book.

However, as 2% Ag solder paste, sometimes more ease to be oxidise, so the paste flux used is sometimes stronger than the corresponding 62/3 paste.

Base on my experience, I find 2% Ag seems more or less of similar soldering ability as 63/37. However, if you really er some tomb stoning problems (I haven't heard about this from my colleagues), first you can adjust your reflow profile. If it still not help, you can try on some tin/lead paste with 2-3% Bi. Quite common in Japan and Europe.

I also find that even using 2% Ag, sometimes it helps can't help to reduce the "gold scavaging", it depends on th thickness of the gold plated. In my experience, on Ni-Au board, after reflow, it always very difficult for me to find the gold layer (via SEM/EDX).

Victor

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Brian Sloth Bentzen

#11994

Re: 2% silver solder paste | 19 April, 1999

| We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated. |

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Brian Sloth Bentzen

#11995

Re: 2% silver solder paste | 19 April, 1999

| | We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated. | | Hi Rob

At my company we have used solder paste with 2% Ag the last 10 years and have seen no problems to that. We produce both HAL and NIAu plated boards. For your information nearly all companies in scandinavia uses on paste containing 2% Ag. The reason for this was earlier use of silver paladium on component terminals. So I guess we just hang on to this type of paste even though it is not necesary.

Brian

| Rob | We have been using Sn62Pb36Ag on HASL SnPb for six months with no apparent problems | | Terry | |

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JohnW

#11996

Re: 2% silver solder paste | 22 April, 1999

| | We process both tin/lead plated boards and gold plated boards in our surface mount group. I have used Sn62/Pb36/Ag2 solder paste on all gold plated boards to help prevent gold scavaging. To reduce the amount of different solder pastes we have to buy I would like to use this same chemistry on our tin/lead boards. Currently I use Sn63/Pb37 on tin/lead boards. Have any of you experimented with this chemistry? I ran some tin/lead test boards with the Ag2 paste and could see no discernible difference. Any input would be appreciated. | | | Rob: Several points: | | 1 We used 2% Ag solder on HASL boards for years with no known problems. | 2 Ag can improve solder flow across solderable surfaces. | 3 If you have too much Ag in your solder joints, you can get into real trouble with brittle and weak Ag3Sn intermetallic compounds. Components can literally fall off boards, as a result of this IM. | 4 It seems that Jennie Hwang wrote an article on 2% in "SMT" magazine not too long ago. | | On your using 2%: | | 1 I've never heard that 2% has a positive impact on Au plated boards. What is the basis for your approach? | 2 I am not aware of "gold scavaging" or how how Ag would prevent it. What's the background on this? | 3 I am painfully aware that Au plating thickness affects solder connections. (Others have posted several threads on SMTnet.) | | TTYL | | Dave F | Dave, The 2% silver stops the gold from migrating into the solder. This is basically because the gold fit's the spaces between the tin/lead molecules so it disapear's into the solder and give's u sonme real trouble some joints. The 2 % silver fill's the gap's in the crystal lattice of the solder joint to block the migration of the gold into the solder.( shees must have been awake in that materials class after all) anyway's them's the basic's I think, unless I'm confused again, it happen's but I'm pretty confident on this.

see ya

John

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