Phone Icon0208 953 1211       Email

Cart empty

Indium 3.1 Water Soluble Pb Free Solder Paste

Manufacturer: Indium


• Exceptional printing
• Long stencil life
• Wide reflow profile window
• Outstanding slump resistance
• Excellent wetting compatibility
• Superior fine-pitch soldering ability
• Low voiding
• Low foam


Indium Corporation manufactures low-oxide spherical powder composed of a variety of Pb-Free alloys that cover a broad range of melting temperatures. Type 3 powder is the standard of fering with Sn/Ag/Cu, Sn/Ag and other Pb-Free alloy systems. The metal percent is the weight percent of the solder powder in the solder paste and is dependant upon the powder type and application.

Standard Product Specifications

Alloy Metal Load Particle Size

Indalloy #241 Printing Dispensing 25-45 µm
95.5Sn/3.8Ag/0.7Cu 88.5% 83% 0.001-0.0018”
Indalloy #256
Indalloy #121


Standard packaging for stencil printing applications includes 500g jars and 500g car tridges. Other packaging options may be available upon request.

Storage and Handling


Refrigerated storage will prolong the shelf life of solder paste. The shelf life of Indium3.1 is no less than 4 months when stored at less than 10°C.
Solder paste should be allowed to reach ambient working temperature prior to use (about 4-6 hours). Actual time to reach thermal equilibrium will var y with container size. Paste temperature should be verified before use. Use paste within 8 hours of exposure to atmosphere. Jars and car tridges should be labeled with date and time of opening.
When storing solder paste contained in syringes and car tridges, the solder paste should be stored with the tip down.

Technical Support

Indium Corporation’s internationally experienced engineers provide in-depth technical assistance to our customers. Thoroughly knowledgeable in all facets of Material Science as it applies to the electronics and semiconductor sectors, Technical Suppor t Engineers provide exper t advice in solder proper ties, alloy compatibility and selection of solder preforms, wire, ribbon and paste. Indium Corporation’s Technical Suppor t engineers provide Rapid Response to all technical inquiries.

Material Safety Data


The MSDS for this product can be found online at y/msds.php







J-STD-004A* (IPC-TM-650)

• Flux Type (per J-STD-004A)

• Flux Induced Corrosion

• Presence of Halide Silver Chromate Fluoride Spot Test

Quantitative Halide Content

• SIR (cleaned)







J-STD-005 (IPC-TM-650)

• Typical Solder Paste Viscosity

SAC387 (Sn95.5/Ag3.8/Cu0.7, Type 3, 89%)

SAC305 (Sn96.5/Ag3/Cu0.5, Type 3, 88.5%) Malcom (10 rpm),

• Typical Tackiness

• Slump Test

• Solder Ball Test

1950 poise

35g Pass Pass

All information is for reference only. Not to be used as incoming product specifications.

*J-STD-004A has replaced J-STD-004 and is more stringent in its requirements.


The sharp print definition of Indium3.1 is ideal for fine- pitch applications. The unprecedented stencil life of this water-soluble product vir tually eliminates waste of solder paste.

Printer Operation:

The following are general recommendations for stencil printer optimization for Indium3.1. Adjustments may be necessar y based on specific process requirements:
• Solder Paste Bead Size: 20-25mm diameter
• Print Speed: 25-100mm/sec
• Squeegee Pressure: 0.018-0.027kg/mm of blade length
• Underside Stencil Wipe: Once ever y 10-25 prints or as necessary
• Solder Paste Stencil Life: >8 hrs. @ 20-50% RH& 22-28°C ~4 hrs. @ 50-70% RH & 22-28°C


Indium3.1 exhibits excellent wetting under both air and nitrogen reflow atmosphere. The solder joints yielded are shiny and smooth, including those of ultra fine-pitch components. Indium3.1 has low voiding performance, including joints of BGAs and CSPs.


Residue Cleaning: Indium3.1 residue is easily cleaned with water at no less than 60 psi and 55°C. The optimal spray pressure and temperature are a function of the board complexity and the efficiency of cleaning equipment.
Stencil Cleaning: This is best per formed using an automated stencil cleaning system for both stencil and misprint cleaning to prevent extraneous solder par ticles. Most commercially available stencil cleaners and isopropyl alcohol (IPA) work well.


Recommended Profile:

The above reflow profile was designed to serve as a star tiing point for process optimization using Indium3.1. When seeking to minimize thermal gradient or reduce voiding in BGA assemblies, a profile utilizing a soak of up to 2 minutes at 205-210°C may help.

Heating Stage:

A linear ramp rate of approximately 1°C/second allows gradual evaporation of volatile flux constituents and prevents defects such as solder balling/beading and bridging as a result of hot slump. It also prevents unnecessar y depletion of fluxing capacity when using higher temperature alloys.

Liquidus Stage:

A peak temperature of 10-35°C (240°C shown) above the melting point (217°C) of the solder alloy is needed to form a quality solder joint and
achieve acceptable wetting due to the formation of an intermetallic layer. If the peak temperature is excessive, or the time above liquidus greater than the recommended 45-90 seconds, flux charring, excessive intermetallic formation and damage to the board and components can occur.

Cooling Stage:

A rapid cool down is desired to form a fine grain structure. Slow cooling will form a large grain structure, which typically exhibits poor fatigue resistance. The acceptable cooling range is 0.5°C-6.0°C/second (2.0°-6.0°C/second is ideal).

This product data sheet is provided for general information only. It is not intended, and shall not be construed, to warrant or guarantee the performance of the products described which are sold subject exclusively to written warranties and limitations thereon included in product packaging and invoices.



Conro Electronics Ltd
Unit 7, Orbital 25, Dwight Road, Watford, Hertfordshire
WD18 9DA

delivery van icon


We offer next day and Saturday deliveries excluding orders made after 3pm weekdays, weekends and public holidays.

AS 9120B

Conro Electronics Ltd certified to the AS 9120B (Aerospace) standard

Click Here To View Our Certificate

ISO 9001:2015

Conro Electronics Ltd certified to ISO 9001:2015

Click Here To View Our Certificate