Kester HM531 Solder Paste 7010020511 | Sn63/Pb37 Leaded Water-Soluble ORM0 | 600g Cartridge | Case of 10
Kester HM531 Solder Paste — 7010020511 | Sn63/Pb37 Leaded Water-Soluble ORM0 | 600g Cartridge | Case of 10
Kester HM531 (SKU: 7010020511) is a halide-free, organic acid, water-soluble leaded solder paste formulated with Sn63/Pb37 eutectic alloy (183°C melting point). HM531 delivers the highest level of batch-to-batch consistency and performance in its class — providing hours of stable stencil life, tack time, and repeatable brick definition regardless of idle time, print speed, or lot variation. HM531’s aggressive activator package provides superior wetting to OSP-coated PCBs and PdAg components. The anti-slump chemistry, consistent print volumes, excellent solderability, and easy water washability make HM531 an ideal choice for any leaded water-soluble SMT application. Classified ORM0 per IPC J-STD-004. Sold as a case of 10 × 600g cartridges. Ships overnight due to refrigeration requirements.
Key Specifications
| Specification | Value |
|---|---|
| Part Number / SKU | 7010020511 |
| Product Line | HM531 |
| Alloy | Sn63/Pb37 — Eutectic Leaded |
| Melting Point | 183°C (eutectic — sharp melt, no pasty range) |
| Flux Type | Halide-Free Organic Acid, Water-Soluble |
| Flux Classification | ORM0 (per IPC J-STD-004) |
| Reflow Atmosphere | Air |
| Surface Finish Compatibility | OSP, PdAg (Palladium-Silver), and wide variety of metallic substrates |
| Container | 600g cartridge |
| Sold As | Case of 10 cartridges (6kg total) |
| Post-Reflow Cleaning | Required — water wash |
| Compliance | IPC J-STD-004 ORM0; Note: Sn63/Pb37 is leaded — not RoHS compliant for restricted applications |
| Brand | Kester |
| Shipping Requirement | Overnight only (temperature-sensitive) |
Key Features
- Sn63/Pb37 eutectic alloy at 183°C — true eutectic composition with no pasty range; sharper solidification than non-eutectic alloys; lower reflow temperature than lead-free SAC alloys (217–220°C)
- Exceptional batch-to-batch consistency — stable stencil life and tack time lot after lot; consistent solder paste volume regardless of idle time, stencil life, or print speed variation
- Aggressive halide-free organic acid activator — superior wetting on OSP-coated PCBs and PdAg (Palladium-Silver) components where standard flux systems may underperform
- Anti-slump chemistry — maintains precise brick definition and deposit geometry between print and reflow; minimizes bridging risk on fine-pitch components
- Outstanding cleanability — water-soluble residues clean effectively with standard DI water wash equipment; low residue burden post-wash
- ORM0 classified — halide-free organic acid flux per IPC J-STD-004; suitable for applications requiring halide-free water-soluble chemistry
- 600g cartridge, case of 10 — sealed cartridges for automated paste dispensing; case format optimizes refrigerated shipping and production inventory
Frequently Asked Questions
When should I use Kester HM531 (leaded) instead of a lead-free water-soluble paste like R520A?
HM531 is the right choice when your application is exempt from RoHS restrictions (military, aerospace, medical, legacy systems, or components not rated for lead-free reflow temperatures). Sn63/Pb37 reflowsat 183°C vs SAC305 at 217–220°C — a significant thermal advantage for temperature-sensitive components and assemblies. If RoHS compliance is required, use R520A or another lead-free water-soluble paste.
What is the advantage of a eutectic Sn63/Pb37 alloy?
Eutectic 63/37 has a single melting point (183°C) with no pasty range — meaning it transitions sharply from solid to liquid and back. This produces more consistent, well-defined solder joints compared to non-eutectic alloys, and allows tighter reflow profile control. It is the historical standard for leaded SMT assembly.
Is post-reflow cleaning required with HM531?
Yes — HM531 is a water-soluble paste and post-reflow water washing is required. Organic acid residues left on the board are hygroscopic and can cause electrochemical reliability issues if not removed. Use standard DI water wash equipment per your cleaning process SOP.
What surface finishes does HM531 work best on?
HM531’s aggressive activator is particularly effective on OSP (Organic Solderability Preservative) coated PCBs and PdAg (Palladium-Silver) components. It also performs well on HASL, ImSn, ImAg, and other standard metallic substrates.
Is Kester HM531 RoHS compliant?
No — HM531 uses Sn63/Pb37 (leaded) alloy and is not RoHS compliant. It is intended for applications exempt from RoHS lead restrictions. Confirm your application’s regulatory status before ordering. Contact MTE Solutions at 651-600-3838 for guidance on selecting the appropriate alloy for your requirements.
Why does solder paste require overnight shipping?
Solder paste is temperature-sensitive and must be shipped and stored refrigerated to preserve flux activity, viscosity, and shelf life. Refrigerate immediately upon receipt and allow to reach ambient temperature before use.
