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Indium 3.2 Water Soluble Pb Free Solder Paste

Manufacturer: Indium


• Consistent fine-pitch printing per formance with high transfer efficiency from stencil apertures
• Superior fine-pitch soldering ability
• Wide reflow profile window
• Excellent response-to-pause printing per formance
• Outstanding slump resistance
• Low voiding
• Minimal foaming during the cleaning process
• Excellent wetting


Indium3.2 is an air or nitrogen reflow, water-soluble solder paste specifically formulated to accommodate the higher processing temperatures required by the Sn/Ag/Cu, Sn/Ag, Sn/Sb, and other Pb-Free alloy systems. This product formulation of fers consistent, repeatable printing per formance combined with a long stencil life and sufficient tack strength to handle the challenges of today’s high-speed as well as high-mix sur face mount lines. In addition to consistent printing and reflow requirements, this solder paste of fers superb wetting to the various Pb-Free metallizations and has exceptional low voiding per formance on fine-pitch components, including BGA’s and CSP’s.


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 Sn/Sb 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


Metal Load


96.5Sn 3.0Ag 0.5Cu (SAC305)

88.5% Printing


95.5Sn 3.8Ag 0.7Cu (SAC387)

88.5% Printing



Indium3.2 is currently available in 500g jars or 600g car tridges. Packaging for enclosed print head systems is also readily available. Alternate packaging options may be available upon request.

Storage and Handling Procedures

Refrigerated storage will prolong the shelf life of solder paste. The shelf life of Indium3.2 is no less than 4 months when stored at <5°C. Solder paste packaged in car tridges and syringes should be stored tip down.

When refrigerated, solder paste should be allowed to reach ambient working temperatures prior to use. Generally, paste should be removed from refrigeration at least 2 hours before use. Actual time to reach thermal equilibrium will var y with the container size and the solder paste temperature should be verified before use. Jars and car tridges should be labeled with the date and time of opening. It is not recommended to remove worked paste from the stencil and mix it with the unused paste in the jar, because this may alter the rheology of the unused paste.


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

• Flux Type (per J-STD-004A) ORM1

• Flux Induced Corrosion M

• Presence of Halide

Silver Chromate Pass

Fluoride Spot Test Pass

Quantitative Halide Content <0.7% Cl equivalent

•SIR (cleaned) Pass


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

•Typical Solder Paste Viscosity

SAC305 (Sn96.5/Ag3/Cu0.5,

Type 3, 88.5%)

Malcom (10 rpm) 1750 poise**

•Typical Tackiness 50g**

•Slump Test Pass

•Solder Ball Test Pass

• Thixotropic Index (ICA Test) -.60

**The repor ted value is a running average subject to periodic updates.

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

*The most current revision of the applicable IPC Joint Industr y Standard shall always be referenced.


Stencil Design:

Electroformed and laser cut/electropolished stencils produce the best printing characteristics among stencil types. Stencil aper ture design is a crucial step in optimizing the print process. The following are a few general recommendations:

Discrete components — A 10-20% reduction of stencil aper ture has significantly reduced or eliminated the occurrence of mid-chip solder beads. The “home plate” design is a common method for achieving this reduction.

Fine pitch components — A surface area reduction is recommended for apertures of 20 mil pitch and finer. This reduction will help minimize solder balling and bridging that can lead to electrical shor ts. The amount of reduction necessar y is process dependent (5-15% is common).

For optimum transfer efficiency and release of the solder paste from the stencil aper tures, industry standard aper ture and aspect ratios should be adhered to.

Printer Operation:

The following are general recommendations for stencil printer optimization. Adjustments may be necessary based on specific process requirement:
• Solder Paste Bead Size: 20-40mm diameter
• Print Speed: 12-150mm/sec
• Squeegee Pressure: 0.018-0.027kg/mm of blade length
• Underside Stencil Wipe: Star t at once every 5 prints, then decrease frequency until an
optimum value is determined.
• Solder Paste Stencil Life: >8 hrs. <60% RH & 22-28°C


Residue Removal

Indium3.2 flux residues are water-soluble and best re-
moved by an inline or batch type cleaning process using
spray pressure and heated DI water. A spray pressure
of 60 PSI and a DI water temperature of 55°C can be
used as a star ting point. The optimal spray pressure
and temperature are a function of board size, complex-
ity and the efficiency of the cleaning equipment and
should be optimized accordingly.

Stencil Cleaning

This is best per formed using an automated stencil
cleaning system for both stencil and misprint cleaning
to remove extraneous solder par ticles. Most commercially
available stencil cleaners and isopropyl alcohol are

Compatible Products

• Rework Flux: TACFlux® 025
• Flux Pen: FP-300
• Cored Wire: CW-301
• Wave Flux: 1095-NF

Heating Stage:

A linear ramp rate of 0.5°- 2.0°C/second allows gradual evaporation of volatile flux constituents and helps minimize defects such as solder balling and/or beading and bridging resulting from hot slump. It also prevents unnecessar y depletion of fluxing capacity when a high peak temperature and extended time above liquidus is used.

Liquidus Stage:

Indium3.2 can accommodate a peak temperature range of 235°C to 260°C. The actual peak temperature is determined by the board size, complexity, and component limitations. The time above liquidus (TAL) should be 30–90 seconds. A peak temperature and TAL above these recommendations can result in excessive intermetallic formation that can decrease solder joint reliability.

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).



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

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