SACm® Soldering Alloy
- Easily substituted into existing Pb-free processes
- Comparable reliability to SAC305 and SnPb eutectic
- Superior drop shock resistance
- Maintains thermal cycling reliability with Mn
- Superior drop shock resistance
- Maintains thermal cycling reliability with Mn
Current Industry Dilemma:
Conventional SAC alloys exist with an inherent trade-off between thermal cycling reliability (TCR) and drop shock resistance (DSR). High Ag versions do not live up to the expectations of SnPb DSR, whereas low Ag versions offer improved DSR, but lose TCR.
The Solution:
With the addition of Mn, SACm®does not compromise on reliability. The combination of low Ag, for lower material costs and improved TCR over other low Ag alloys, integrates easily into existing Pb-free processes.
The Details:
SACm® is comprised of 97.5-98.5% Sn, 0.5-1.0% Ag, and 0.5-1.0% Cu, with dopant levels of Mn. This alloy is available in solder spheres as well as powder (T3, T4, and T4.5) and solder paste.
SACm® Basic Material Properties
| SACm® | SAC105 | SAC305 | |
|---|---|---|---|
| Melting Point Solidus °C Liquidus °C |
217 226 |
217 225 |
217 220 |
| Tensile Strength (PSI) |
5625 | 5640 | 7200 |
| Yield Strength (PSI) |
3590 | 3359 | 5289 |
| Young's Modulus (KSI) |
2110 | 2150 | 2410 |
| Elongation (%) |
15.7 | 13.4 | 19.3 |
JEDEC Drop Test Performance
Typically, improved drop shock resistance is achieved with low Ag content SAC solder alloys. However, SAC105 (or even SAC0307) still does not equal the DSR of SnPb eutectic alloys. SACm® delivers significantly improved DSR, rivaling SnPb drop shock performance.
Testing Conditions:
- Components – 0.5mm pitch BGA
- PCB – 8 layer FR4 with OSP finish
- Test Conditions – JESD22-B111
- Preconditioning – 250 cycles of thermal cycling
Thermal Cycling
Low Ag content will also have the trade-off of compromised thermal cycling reliability. SACm® boosts TCR, greatly outperforming SAC105, and is comparable to SAC305.
Testing Conditions:
- Components – 0.5mm pitch BGA
- PCB – 8 layer FR4 with OSP finish
- -40oC to +125oC; 42 min/cycle; 10 minute dwells
Preconditioning:
- Bake at 150°C for 250 hours
How SACm® Works
The addition of Mn helps improve reliability in two ways: it refines and limits the IMC formed, and, over time, impedes intermetallics growth and grain coarsening. A thin IMC layer shows improved DSR and TCR, whereas Mn further improves TCR by minimizing IMC layer growth.
SACm® shows an insignificant decline in shear testing after aging due to Mn maintaining the IMC layer thickness (see graph on right).
Cross sections (below), show the IMC layer before and after 1000 hours of aging. It is evident that the amount of intermetallic growth is drastically reduced, mirroring the improved reliability results.
SACm® Solder Paste
SACm® solder powder is available in IPC standard T3, T4, and Indium’s T4.5 for optimal miniaturized printing applications. Indium Corporation provides top quality solder pastes for PCB assembly. To meet individual assembly needs, several fluxes from the Pb-free series of fluxes are offered with SACm®.
Shared features:
- First-class printing performance
- Consistent print transfer through apertures with area ratios ≤0.66
- Long stencil life and forgiving response-to-pause
- High component retention tack prevents components from shifting
- Robust reflow performance
- Unique oxidation barrier technology to eliminate defects during reflow
- Wide process window for flexible reflow profiling
- Good wetting performance on various surface finishes
| Paste Name (Flux) | Halogen-Free? | Powder Size | Stencil Printing Metal Load |
Features |
|---|---|---|---|---|
| Indium8.9 | No | T3 T4 |
88.50% 88.25% |
Eliminates HIP |
| Indium10.1 | No | T3 T4 |
88.75% 88.50% |
Lowest Voiding |
| Indium8.9HF | Yes | T3 T4 |
89% 88.50% |
HF versatile performance |
| RMA-155 | Yes | T3 T4 |
89% 88.50% |
RMA for modern challenges |
Related Markets and Applications
Top SACm® Technical Documents
Indium8.9 Pb-Free Solder Paste (US Letter)
Product Data Sheet
Indium8.9 Pb-Free Solder Paste (A4)
Product Data Sheet
Achieving High Reliability Low-Cost Lead-Free SAC Solder Joints via Mn Doping (Paper)
Technical Paper
The Second Generation Shock Resistant and Thermally-Reliable Low Ag SAC Solder with Mn (Paper)
Technical Paper
SACm® Blog Posts
Tech Seconds: What is a Shoulder Reflow Profile?
In this installment of Tech Seconds, Phil describes when to use a shoulder profile.
The Right Solder Alloy for the Right Application
Indium Corporation is the leading expert in solder alloy selection...the right alloy for the right application.
Fluxless Soldering of 80Au/20Sn with Forming Gas/Inert Atmosphere
Soldering without flux is generally regarded as difficult if not impossible. Yet a fluxless process is routinely done with 80Au/Sn ribbon and preforms - I'll tell you how.
For comments or questions about the content on this page, please contact:
Christopher Nash
Product Manager PCB Assembly Materials
cnash@indium.com
From One Engineer to Another®
All of Indium Corporation’s products and solutions are designed to be commercially available
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