CHOOSE THE RIGHT MELT. BUILD A BETTER JOINT.
Professional solder wire for electronics repair, rework, and assembly. Choose 138°C lead-free Low Melt for reduced heat exposure or 183°C Sn63/Pb37 Medium Melt for dependable everyday soldering performance.
PolarTronix Solder Wire
Different soldering jobs require different thermal profiles. PolarTronix Low Melt and Medium Melt Solder Wire give technicians two professional options for precision electronics repair, rework, and assembly.
Low Melt / Lead-Free
138°C
280°F Melting Point
Lead-free low-temperature solder wire designed for precision electronics repair and rework where reducing heat exposure can be beneficial.
Medium Melt / Eutectic
183°C
361°F Melting Point
Eutectic solder wire designed for dependable everyday electronics soldering, PCB repair, assembly, and professional rework applications.
Which One?
Choose 138°C Low Melt when lower melting temperature and reduced heat exposure are important. Choose 183°C Medium Melt for dependable general electronics soldering and everyday professional repair work.
Low Melt vs. Medium Melt
Both PolarTronix solder wires are designed for professional electronics work, but their alloy, melting point, wire diameter, and ideal use cases differ. The right choice depends on how much heat the repair can tolerate and the type of soldering work being performed.
| Specification | Low Melt | Medium Melt |
|---|---|---|
| Alloy | Sn42 / Bi58 | Sn63 / Pb37 |
| Composition | 42% Tin / 58% Bismuth | 63% Tin / 37% Lead |
| Melting Point | 138°C / 280°F | 183°C / 361°F |
| Lead-Free | Yes | No |
| Wire Diameter | 0.5 mm | 0.8 mm |
| Net Weight | 50 g | 50 g |
| Primary Advantage | Lower heat exposure | General-purpose soldering performance |
| Best Fit | Precision, delicate, heat-sensitive rework | Everyday electronics soldering and repair |
Choose Low Melt When
The 138°C Sn42/Bi58 alloy is especially useful when a lower melting temperature can help reduce the amount of heat introduced during delicate electronics rework.
Choose Medium Melt When
The 183°C Sn63/Pb37 eutectic alloy is a dependable choice for general electronics soldering, repair, prototyping, assembly, and repeatable professional work.
Important
The 138°C and 183°C values describe the melting points of the solder alloys. Actual soldering-station temperature depends on factors such as joint size, tip geometry, thermal mass, equipment, workflow, and the components being serviced.
Ideal Applications
Both PolarTronix solder wires are built for professional electronics work. The main difference is where each alloy provides the strongest advantage: Low Melt for lower-temperature precision rework, and Medium Melt for dependable everyday soldering.
01 / PCB REPAIR
Suitable for professional circuit-board repair, component replacement, solder-joint service, and electronics rework.
02 / MICRO
Useful for detailed electronics work where controlled solder delivery and consistent alloy behavior are important.
03 / SMD & SMT
Supports SMD and SMT repair workflows involving small electronic components and board-level connections.
04 / DEVICES
Fits professional mobile-device repair, connector service, board repair, and component-level soldering workflows.
05 / CONSOLES
Suitable for console motherboard repair, connector service, component replacement, and general electronics rework.
06 / COMPUTERS
Useful for computer motherboard repair, power circuits, connectors, through-hole components, and general soldering.
Low Melt Stands Out For
The 138°C Sn42/Bi58 alloy is especially useful when reducing the amount of heat introduced to the repair area is a priority.
Medium Melt Stands Out For
The 183°C Sn63/Pb37 eutectic alloy is a dependable general-purpose option for routine repair, assembly, prototyping, and professional electronics work.
Professional Electronics
PCB Repair · Microsoldering · SMD / SMT · Connectors · Consoles · Mobile Devices · Computers · Prototyping
Alloy Selection
The best solder wire is not determined by melting point alone. Consider the component, PCB construction, thermal sensitivity, joint size, soldering equipment, and the alloy already present when selecting the appropriate material.
Melting Temperature
The melting point tells you when the solder alloy transitions into a liquid state. PolarTronix Low Melt and Medium Melt Solder Wire use different alloys, giving technicians two distinct thermal profiles for different repair and assembly requirements.
Sn42 / Bi58 Low Melt
138°C
280°F Melting Point
Sn42/Bi58 melts at 138°C, allowing the solder alloy to transition at a lower temperature than conventional Sn63/Pb37 solder. This can be useful when reducing thermal exposure during delicate electronics rework.
Sn63 / Pb37 Medium Melt
183°C
361°F Melting Point
Sn63/Pb37 is a eutectic alloy with a defined 183°C melting point, providing a direct transition between solid and liquid states during general electronics soldering and repair.
Important Distinction
The alloy melting temperature does not tell you exactly what temperature to set your soldering station. The iron tip must transfer enough energy into the joint for the solder and surrounding materials to reach the required working temperature.
01 / THERMAL MASS
Large ground planes, connectors, and heavier joints absorb more heat than small component leads.
02 / TIP
Tip shape and contact area influence how efficiently heat transfers from the soldering iron into the joint.
03 / EQUIPMENT
Heater power, temperature recovery, calibration, and tip condition can all affect soldering performance.
04 / WORKFLOW
Component sensitivity, board design, existing alloy, flux, and repair technique all influence the working temperature required.
Step 01
Choose Low Melt or Medium Melt according to the repair, existing solder system, component sensitivity, and desired thermal profile.
Step 02
Use an appropriate soldering tip, station, and flux for the size and thermal mass of the joint being serviced.
Step 03
Use enough heat for efficient solder flow while avoiding unnecessary heating time around sensitive components and board materials.
Key Principle
Successful soldering depends on the complete thermal system—not just the number on the station display. Alloy, flux, joint mass, tip geometry, equipment performance, and contact time all work together during a soldering process.
Product Details
PolarTronix Low Melt and Medium Melt Solder Wire provide two distinct alloy and temperature options for professional electronics repair, rework, prototyping, and assembly.
138°C
Low Melt / Sn42-Bi58
183°C
Medium Melt / Sn63-Pb37
0.5 / 0.8 mm
Wire Diameter Options
50 g
Each Spool
Low Melt
Lead-free low-temperature solder wire for precision and heat-sensitive electronics rework.
Alloy
Sn42 / Bi58
Composition
42% Tin / 58% Bismuth
Melting Point
138°C / 280°F
Lead-Free
Yes
Wire Diameter
0.5 mm
Net Weight
50 g
Best Fit
Precision rework, heat-sensitive components, connector service, BGA work, and detailed electronics repair
Medium Melt
Eutectic solder wire for dependable everyday professional electronics soldering and assembly.
Alloy
Sn63 / Pb37
Composition
63% Tin / 37% Lead
Melting Point
183°C / 361°F
Lead-Free
No
Wire Diameter
0.8 mm
Net Weight
50 g
Best Fit
General PCB repair, through-hole soldering, electronics assembly, prototyping, and everyday professional bench work
Low Melt
138°C melting point supports lower-temperature rework where reducing thermal stress is beneficial.
Medium Melt
Sn63/Pb37 transitions directly at 183°C for dependable general electronics soldering.
Wire Control
Two wire diameters support finer precision feeding and broader general-purpose solder delivery.
Professional Size
Practical spool size for professional repair benches, technical labs, and regular soldering workflows.
Related Products
Pair PolarTronix solder wire with flux, solder paste, desoldering tools, precision handling tools, and cleaning products for a complete professional electronics repair and rework setup.
Soldering Flux
Professional flux for soldering, microsoldering, component rework, connector service, and precision PCB repair.
View ProductLow-Temperature Paste
Sn42/Bi58 lead-free solder paste with a 138°C melting point for controlled low-temperature electronics rework.
View ProductMedium-Temperature Paste
Sn63/Pb37 eutectic solder paste for professional PCB repair, assembly, and electronics rework.
View ProductDesoldering
Spring-loaded ESD-safe desoldering pump for controlled removal of molten solder during electronics rework.
View ProductPrecision Handling
Straight and curved ceramic-tip tweezers for handling small components during soldering and electronics repair.
View ProductPCB Cleaning
Fine cleaning brush for detailed PCB cleaning, soldering-residue work, and professional repair-bench use.
View ProductSoldering Workflow
Build a controlled repair process around flux preparation, solder delivery, component handling, desoldering, and final cleaning.
Flux → Solder → Rework → Clean
Explore the full PolarTronix range of soldering materials, electronics repair tools, cleaning products, and professional bench supplies.
View All ProductsPolarTronix Professional Solder Wire
Choose 138°C Sn42/Bi58 Low Melt for lower-temperature, precision electronics rework, or 183°C Sn63/Pb37 Medium Melt for dependable everyday soldering, PCB repair, assembly, and professional bench work.
Low Melt
138°C / 280°F
Sn42/Bi58 · Lead-Free · 0.5 mm · 50 g
Medium Melt
183°C / 361°F
Sn63/Pb37 · 0.8 mm · 50 g