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Features

• High transfer efficiency through small apertures (≤ 0.66AR)
• Excellent wetting to all common finishes at high and low peak reflow temperatures
• Clear, probe testable flux residue
• Eliminates head-in-pillow defects

Introduction

Indium8.9 is an air or nitrogen reflow, no-clean solder paste specifically formulated to accommodate the higher processing temperatures required by the SnAgCu, SnAg, and other alloy systems favored by the electronics industry to replace conventional Pb-bearing solders. Indium8.9 offers unprecedented stencil print transfer efficiency to work in the broadest range of processes. In addition, the high probe testability of Indium8.9 minimizes false failures in ICT.

Alloys

Indium Corporation manufactures low-oxide spherical powder composed of a variety of Pb-Free alloys that cover a broad range of melting temperatures. Type 4 and Type 3 powder are standard offerings with SAC alloys. 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 offerings are detailed in the table on the right.

Packaging

Indium8.9 is currently available in 500g jars or 600g cartridges. Packaging for enclosed print head systems is also readily available. Alternate packaging options may be available upon request.

Standard

Product Specifications

Storage and Handling

Procedures

Refrigerated storage will prolong the shelf life of solder paste. The shelf life of Indium8.9 is 6 months when stored at <10°C. Solder paste packaged in cartridges should be stored tip down.
Solder paste should be allowed to reach ambient working temperature prior to use. Generally, paste should be removed from refrigeration at least two hours before use. Actual time to reach thermal equilibrium will vary with container size. Paste temperature should be verified before use. Jars and cartridges should be labeled with date and time of opening.

BELLCORE AND J-STD TESTS & RESULTS

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

• Flux Type (per J-STD-004A) - ROL1
• Flux Induced Corrosion (Copper Mirror) - Type L
• Presence of Halide
  Silver Chromate - Pass
  Fluoride Spot Test - Pass
  Ion Chromatography - <0.5% Cl- eq.
• Post Reflow Flux Residue (ICA Test) - 35%
• SIR - Pass

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

• Typical Solder Paste Viscosity
  Type 4 (800420) 2000 poise
  Type 3 (800449) 1750 poise
  Malcom (10 rpm)

• Slump Test - Pass
• Solder Ball Test - Pass
• Typical Tackiness - 50g
• Wetting Test - Pass

BELLCORE GR-78

• SIR - Pass
• Electromigration - Pass

Printing

Stencil Design:

Electroformed and laser cut/electropolished stencils produce the best printing characteristics among stencil types. Stencil aperture 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 aperture 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 shorts. The amount of reduction necessary is process dependent (5–15% is common).
• For optimum transfer efficiency and release of the solder paste from the stencil apertures, industry standard aperture 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: 20–25mm diameter
• Print Speed: 25–100mm/sec
• Squeegee Pressure: 0.018–0.027kg/mm of blade length
• Underside Stencil Wipe: Start at once every 5 prints then decrease frequency until an optimum value is determined.
• Solder Paste Stencil Life: >8 hrs. @ 30–60% RH & 22°–28°C

Cleaning

Indium8.9 is designed for no-clean applications, however, the flux can be removed if necessary by using a commercially available flux residue remover.
Stencil Cleaning is best performed using isopropyl alcohol (IPA) as a solvent. Most commercially available stencil cleaners work well.

Compatible Products

• Rework Flux: TACFlux® 020B, TACFlux® 089
• Cored Wire: CW-501, CW-801
• Wave Flux: WF-7742, WF-9942

Reflow

Recommended Profile:

The stated profile recommendations apply to most Pb-free alloys in the SnAgCu (SAC) alloy system, including SAC 305 (96.5Sn/3.0Ag/0.5Cu). This can be used as a general guideline in establishing a reflow profile when using Indium8.9 Solder Paste. Deviations from these recommendations are acceptable, and may be necessary, based on specific process requirements, including board size, thickness, and density.

Heating Stage: The use of a linear ramp rate or ramp-to-spike (RTS) type profile assists in minimizing the greatest overall number of defects associated with the reflow process. If the ramp rate is too fast, it can cause solder balling, solder beading, and aggravated hot slump which can lead to bridging. The ramp rate in the preheat stage of the profile can range from

0.5°–2.5°C/second (0.5°–1°C/second is ideal). A short soak of 20–30 seconds just below the melting point of the solder alloy can help minimize tombstoning when using
a RTS type profile. If necessary, a ramp-soak-spike (RSS) profile can be implemented to minimize voiding on BGA and CSP type packages. A soak zone between 200°–210°C for up to 2 minutes is acceptable.

Liquidus Stage: To achieve acceptable wetting and form a quality solder joint, the acceptable temperature range above the melting point of the solder alloy is 12°–50°C (15°–30°C is

ideal). The acceptable range for time above liquidus (TAL) is 30–100 seconds (45–60 seconds is ideal). 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).

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.