What is the difference between no-clean and water-soluble solder paste?

No-clean solder paste (ROL0 classification) leaves minimal, benign residue after reflow that does not require cleaning. Water-soluble paste (ORH0) uses more aggressive flux activators for better wetting on difficult surfaces, but residues are corrosive and must be removed with deionized water after soldering.

When should I use low-temperature solder paste?

Low-temperature solder paste (BiSnAg alloys, 138-175°C peak reflow) is used when heat-sensitive components like LEDs, flex circuits, or certain connectors cannot withstand standard reflow temperatures of 230-250°C. It is also used in step-soldering processes where a lower-melting joint is needed for a secondary reflow.

What solder paste powder size should I use?

Type 3 powder (25-45 microns) is standard for most SMT applications with 0.5mm pitch and larger. Type 4 (20-38 microns) is recommended for fine-pitch components down to 0.4mm. Type 5 (15-25 microns) is used for ultra-fine features, micro-BGAs, and stencil apertures below 200 microns.

How long can solder paste be stored?

Most Alpha solder pastes have a 6-month refrigerated shelf life at 0-10°C. Once removed from refrigeration, paste should reach room temperature (4-6 hours) before opening to prevent moisture condensation. After opening, paste typically has a 24-72 hour working life depending on the flux system.

Alpha Solder Paste Selection Guide | Technimark

Alpha Solder Paste Selection Guide

Find the optimal solder paste for your SMT assembly process

Lead-Free & Leaded No-Clean & Water-Soluble Type 3/4/5 Powders Authorized Distributor

Alloy Type

Flux Type

Application

Results

Select Alloy Type

Lead-Free (RoHS)

SAC305, SACX Plus, Innolot alloys. 217-221°C melting point. RoHS/WEEE compliant.

Leaded (SnPb)

Sn63/Pb37, Sn62/Pb36/Ag2 alloys. 183°C melting point. Aerospace/military applications.

Low Temperature

BiSnAg, HRL alloys. 138-175°C peak reflow. Temperature-sensitive components.

Alloy Selection Guide

Lead-free alloys are required for most consumer electronics (RoHS compliance). Leaded alloys are still used in aerospace, military, and medical devices with exemptions. Low-temperature alloys reduce thermal stress on sensitive components.

Select Flux Type

Select Application

Recommended Solder Paste

Lead-Free No-Clean Solder Pastes

Product	Alloys	Powder	Key Features	Application
ALPHA OM-353	SAC305, SACX Plus	Type 4, 5	Low HiP/NWO, fine feature, zero-halogen	Leading LF paste, ultra-fine printing
ALPHA OM-362	SAC305, Innolot	Type 4	Ultra-low voiding, IPC Class III, BTC optimized	High reliability, automotive, >125°C
ALPHA OM-340	SAC305, SACX Plus, Innolot	Type 3, 4, 5	Low HiP, excellent pin test, IPC Class III	Broad range, ICT testing critical
ALPHA OM-338	SAC305, SACX Plus	Type 3	Fine feature, ROL0, IPC Class III voiding	General purpose, proven performer
ALPHA CVP-390	SAC305, SACX Plus	Type 3, 4	Zero-halogen, JIS Cu pass, excellent pin test	Best SIR, electrochemical reliability
ALPHA CVP-390V	SAC305, Innolot	Type 4, 5	Best-in-class ECR, >2.0 Cpk at AR 0.60	Automotive harsh environment, fine powder
ALPHA OM-535	SAC305, SACX Plus	Type 4	Lowest voiding, outperforms Indium 8.9HF1	Ultra-low void priority, power devices
ALPHA JP-500	SAC305	Type 5	Jetting optimized, Mydata/Parmi approved	Jet printing only, 30cc syringes

Lead-Free Water-Soluble Solder Pastes

Product	Alloys	Powder	Key Features	Application
ALPHA WS-820	SAC305	Type 3, 4	Halide-free, excellent cleanability, ramp/soak profiles	Cleanable assemblies, high spread/wetting

Low Temperature Solder Pastes

Product	Alloy	Melt Point	Key Features	Application
ALPHA CVP-520	Sn42Bi57.6Ag0.4	138°C	Eliminates wave/selective, zero-halogen	Temp-sensitive PTH, multiple reflow
ALPHA OM-535	SBX02	~140°C	Improved drop shock vs BiSnAg, Type 4	Low temp SMT, consumer electronics
ALPHA OM-565 HRL3	HRL3	175°C peak	Superior drop shock, reduced warpage	Next-gen low temp, chip-scale packages
ALPHA OM-550 HRL1	HRL1	~175°C peak	Improved thermal cycling vs legacy BiSn	Temperature-sensitive CSP assemblies

Leaded Solder Pastes

Product	Alloys	Powder	Flux Type	Application
ALPHA OM-5100	Sn62Pb36Ag2, Sn63Pb37	Type 3, 4	No-Clean (ROL0)	Fine pitch, wide reflow window, LF component compatible
ALPHA OM-5300	Sn63Pb37	Type 3, 4	No-Clean	General purpose leaded
ALPHA WS-809	Sn63Pb37	Type 3	Water-Soluble	Cleanable leaded assemblies
ALPHA CL-78	Sn63Pb37	Type 3	Water-Soluble	High reliability cleanable

Solder Alloy Reference Guide

Lead-Free Alloys

SAC305

Composition: 96.5Sn/3.0Ag/0.5Cu

Melting: 217-221°C

Use: Industry standard, best hole-fill and thermal cycling reliability. Higher cost due to silver content.

SACX Plus 0307

Composition: 99Sn/0.3Ag/0.7Cu + additives

Melting: 217-228°C

Use: Low-silver alternative, ~37% cost savings vs SAC305. Patented formula with anti-drossing elements.

SACX Plus 0807

Composition: 98.5Sn/0.8Ag/0.7Cu + additives

Melting: 217-225°C

Use: Medium-silver, ~27% savings. Performance closest to SAC305. Less competitive displacement.

Innolot

Composition: SnAgCuNiSb

Melting: 206-218°C

Use: High-reliability automotive/aerospace. Superior thermal cycling >125°C operating temps.

SnCX Plus 07

Composition: Sn99.3Cu0.7 + additives

Melting: 227°C

Use: Silver-free, ~41% cost savings. Drop-in for SN100C. No license fee.

Low Temperature Alloys

Sn42Bi57.6Ag0.4

Melting: ~138°C

Peak Reflow: 155-190°C

Use: Standard low-temp BiSn. Eliminates wave/selective for temp-sensitive PTH.

SBX02

Melting: ~140°C

Peak Reflow: 155-190°C

Use: Improved drop shock and mechanical strength vs standard BiSnAg.

HRL1

Peak Reflow: ~175°C

Use: Improved thermal cycling and drop shock. Reduced warpage vs SAC reflow.

HRL3

Peak Reflow: 175°C

Use: Next-gen low temp. Superior thermomechanical performance. Contact rework compatible.

Leaded Alloys

Sn63Pb37

Melting: 183°C (eutectic)

Use: Standard tin-lead. Lowest cost. Wide process window. Aerospace/military exemptions.

Sn62Pb36Ag2

Melting: 179°C

Use: Silver-bearing leaded. Better wetting on silver finishes. Improved joint strength.

Powder Size Reference

Type 3 (25-45µm): Standard SMT, apertures ≥0.5mm. Most common.

Type 4 (20-38µm): Fine pitch, apertures 0.3-0.5mm. 0402/0201 capable.

Type 5 (15-25µm): Ultra-fine, apertures <0.3mm. 01005/008004 capable.

Low Temperature Warning

All components used with BiSn low-temp pastes must be lead-free to prevent formation of tin/lead/bismuth intermetallic with melting point under 100°C. This can cause field failures.