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What is the effect of silver (Ag) alloy in solder paste? What is the differences to expect for solder paste with SAC305 and SAC4

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#87104

Differences between solder paste alloy SAC305 and SAC405. | 23 September, 2021

Hi. Anyone in this forum experienced the lead-free solder paste SAC305 and SAC405? What are the differences to expect for solder paste with SAC305 and SAC405? What is the effect of silver (Ag) alloy in solder paste? It was really appreciated if could share your technical advice or knowledge on this.

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Djo

#87105

Differences between solder paste alloy SAC305 and SAC405. | 23 September, 2021

1)Though in many cases the difference between SAC305 and SAC405 was small,and not always statistically significant, it was observed that SAC405 generally outperformed SAC305 joints. Under 0°C to 100°C thermal cycling,no statistically significant difference between SAC305 and SAC405 was observed at the N1% failure level. Under harsh environment testing, SAC405 joints were significantly better than SAC305 joints,lasting 1.7X longer at the N1% level.Mixed joints based on SAC405 showed very few failures,and had a much lower extent of cracking than mixed joints based on SAC305. Due to the low level of failures in some of the mixed assembly cells, it was not possible to determine if they were statistically different, although the difference appears marked.It is important to note that in each case, the failure mode for SAC305 and SAC405 joints was the same

2) In general high-silver SnAgCu alloys perform poorly in high-strain rate situations(drop shock) but exhibit better thermal fatigue resistance than lower or no Ag alternatives.

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#87109

Differences between solder paste alloy SAC305 and SAC405. | 23 September, 2021

Several articles in a recent SMTnet Express Newsletter [https://smtnet.com/express/index.cfm?fuseaction=archives&issue=20210909] addressed topics of your question.

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#87155

Differences between solder paste alloy SAC305 and SAC405. | 29 September, 2021

"For the lead free soldering of electronic assemblies, the inclusion of silver in the alloy results in better wetting compared to non-silver containing alloys and also allows for a broader process window. Silver also improves joint reliability compared to non-silver lead-free and tin-lead alloys."

Found it in an article here in the library "https://smtnet.com/library/files/upload/Effect%20of%20silver%20in%20common%20leadfree%20alloyspaperEng042309.pdf"

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#87159

Differences between solder paste alloy SAC305 and SAC405. | 1 October, 2021

Thank you Djo for your sharing. By the way, do you know that which field/product will prefer to use SAC405 paste instead of SAC305 or lower Ag wt% alloy solder paste?

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#87160

Differences between solder paste alloy SAC305 and SAC405. | 1 October, 2021

Hi Davef, thank you for your information.

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#87161

Differences between solder paste alloy SAC305 and SAC405. | 1 October, 2021

Thanks, Evtimov. In terms of mechanical drop performance, can we conclude that the higher Ag alloy will have poorer drop shock performance relatively compare to those with lower Ag? The Ag3Sn is a good IMC for welding strength?

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#87162

Differences between solder paste alloy SAC305 and SAC405. | 1 October, 2021

thank you for your information.

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#87164

Differences between solder paste alloy SAC305 and SAC405. | 5 October, 2021

From what I understand SAC305 and SAC405 are considered low silver content and have the better overall mechanical qualities compared to more silver or no silver.

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