What is Low-temperature Solder Paste?
Solder with reflow temperatures ranging from 183 to 221°C has been traditionally used. Nowadays, due to advancements in electronics design, components, and substrates, there is a demand for solder that can reflow within the range of 115 to 180°C – which is also known as low-temperature solder.
Inregarding the metal alloys, low-temperature solder pastes are distinguished by their low melting low temperature and are now widely used in low-temperature SMT assembly thanks to their huge advantages.
| Solder Alloy | Melting Range (ºC) | Typical Peak Reflow Temperature (ºC) |
| Sn63/ Pb37 | 183 | 210 – 220 |
| Sn96.5/Ag3.0/Cu0.5 (SAC305) | 217 – 221 | 240 – 250 |
| Sn99.3/Cu0.7/Ni0.05/Ge0.005 (SN100C) | 227 | 245 – 255 |
| Sn89.0/Ag3.0/Bi0.5/In8.0 | 200 – 205 | 220 – 230 |
|
Sn88.0/Ag3.0/Bi0.5/In8.0 |
197 – 202 | 215 – 225 |
|
Sn48/In52 |
118 | 140 – 150 |
| Sn42/Bi58 | 138 | 160 – 170 |
| Sn/Bi57/Ag-y | 138 – 140 | 160 – 170 |
Why low-temperature solder paste?
The growing need for ultra-thin packages is the primary reason behind the Low-temperature solder paste (LTS) transition. Thinning the package leads to more warping, which results in lower production yields. Additionally, the SnAgCu series solder paste’s reflow temperature is higher than the substrate’s glass transition temperature (Tg), leading to increased warping of both the substrate and PCB. On the other hand, using LTS paste can reduce the reflow temperature to under 200°C, effectively decreasing deformation in both the PCB and substrate.
To list down more key drivers of this trend, we can consider:
- Electronics Components that are affected by temperature (i.e., plastic-capped MEMS or GaAs sensors)
- Components that are susceptible to deformation, melting, or delamination at elevated reflow temperatures. (i.e., 3D-MID plastics, fabrics, or flex circuits)
- Soldering processes that involve multiple steps.
- The aspiration is to reduce reflow expenses.
- Parts that mate with each other and have a notable variance in their coefficient of thermal expansion (CTE).
- Solders that are free of Pb and can be reflowed within the same temperature range as the conventional SnPb and SnPbAg alternatives.
- The temperature range for solder alloys typically consists of indium or bismuth as the base metals.
To evaluate low-temperature soldering materials, there are lots of experiments to take. You can consider Prostech with our supplier’s result here to evaluate our solder paste performance. To make it easier for you to choose the suitable solder paste, please contact our Philippines Representative: