The KAISI 138°C Solder Paste is a professional-grade, low-temperature lead-free solder paste specifically formulated for heat-sensitive soldering applications. With an ultra-low melting point of 138°C, this Sn42/Bi58 (42% Tin, 58% Bismuth) alloy paste is ideal for delicate electronics repair where standard lead-free solder temperatures (217°C) could damage sensitive components or cause PCB warping .

The 138°C variant is particularly well-suited for BGA reballing on multi-layer phone motherboards, CPU repairs, and scenarios where you need to protect adjacent plastic components or flex cables from heat damage. The low thermal stress significantly reduces the risk of board warping and pad lifting, making it a valuable tool in the professional repair shop .

Key Features

• 138°C Ultra-Low Melting Point – Protects heat-sensitive components (CPUs, BGAs, plastic connectors) during rework and prevents PCB warping on thin or multi-layer boards 
• Sn42/Bi58 Lead-Free Alloy Composition – 42% Tin, 58% Bismuth – environmentally friendly and lead-free, complying with RoHS standards 
• Fine 20-38µm Particle Size – Ensures smooth paste flow, prevents stencil clogging, and enables precise application on fine-pitch components and BGA balls 
• Excellent Low-Temperature Wettability – Despite the low melting point, maintains good wetting properties for reliable, strong solder joints
• No-Clean Formula – Leaves minimal flux residue after soldering, reducing post-solder cleaning time
• High Compatibility – This low-temperature SMT paste works well with a wide range of circuit soldering applications, including PTH and SMD assembly 
• Convenient 40g Packaging – Syringe packaging provides precise, waste-free application in tight spaces