Indium 8.9LDA Pb Free Solder Paste for IGBT Module Manufacturing
• Ultra-low voiding, even on large die
• Easily cleaned for high wirebond strength
• High print transfer efficiency using screen or stencil
• Versatile profiling characteristics for optimum results
• Improved process yields and material utilization
Indium8.9LDA is specially designed for IGBT manufacturing. The formulation has been optimized for vacuum reflow soldering of large area die. Ultra-low total voids are possible (typically <0.5%) using a variety of reflow profiles: two examples of suitable vacuum reflow profiles are shown on page 2. The paste is formulated to be cleaned easily using common aqueous-based cleaning solutions. Good cleanability ensures consistently high wirebonding pull-strength. Indium8.9LDA is suitable for application by either screen or stencil printing, and of fers unprecedented print transfer efficiency with a long open life, making it suitable for use in a broad range of processes.
Indalloy 121 (96.5Sn/3.5Ag) is the standard alloy used in IGBT die-attach solder paste, but alternative Pb-Free alloys are also available.
Standard Product Specifications
Indium8.9LDA is currently available in 500g jars or 600g cartridges. Packaging for enclosed print head systems is also readily available. Alternative 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 Indium8.9LDA 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. Best procedure is to store long term in a refrigerator and shor t term line storage at room temperature. Generally, paste should be removed from refrigeration at least six hours before the material is used. Actual time to reach thermal equilibrium will vary with container size. Jars and cartridges should be labelled with date and time of opening.
BELLCORE AND J-STD TESTS & RESU LTS
• 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% CI- eq.
• SIR Pass
• Typical Solder Paste Viscosity
Type 3 1750 poise
• Slump Test Pass
• Solder Ball Test Pass
• Typical Tackiness 50g
• Wetting Test Pass
• SIR Pass
• Electromigration Pass
Indium8.9LDA can be printed by screen or stencil. Thus
large, small and complex apertures can be printed on the same substrate with no loss of efficiency. On larger die size a modified X shape is usually used to aid solder spread and void reduction on reflow, and also to reduce squeegee “scoop”. Response-to-pause and open life
The following are general recommendations for printer optimization. Adjustments may be necessary based on specific process requirement:
A standard flood/print process will give good results, with some basic starter settings as follows:
• Print Speed: 20-75mm/sec
• Squeegee: 80 or 90 durometer diamond
• Snap-of f: Adjust to give the desired bondline thickness in the final solder joint Stencil Print
• Solder Paste Bead Size: 20-25mm diameter
• Print Speed: 50-100mm/sec
• Squeegee Pressure: 0.018-0.027kg/mm of blade length
• Solder Paste Printer Life: >6 hrs. @30-60% RH & (unreplenished) 22°-28°C
Rigorous testing has shown that the reflowed residues of Indium8.9LDA are cleanable to power semiconductor wirebonding standards using recognized aqueous-based flux residue removers. Contact your Indium Corporation Technical Ser vice personnel for recommendations. Stencil or screen cleaning can be per formed using isopropyl alcohol (IPA) as a solvent. Most commercially available stencil cleaners will also work well.
Users should define a suitable vacuum reflow profile that minimizes voids, reduces intermetallic formation, gives good residue cleanability, reduces die skew and die shift, and has good wetting onto metal surfaces.
Liquidus Stage: A peak temperature of 15° to 30°C above the melting point (liquidus) of the solder alloy is recommended to achieve acceptable wetting and form a quality solder joint. The use of higher peak temperatures and longer times-above-liquidus (TAL) will minimize voiding. However, care must be taken with high-tin (Sn) solders and copper (Cu) sur faces that excessive Sn/Cu intermetallics are not formed, as these can lead to dewetting.
A rapid cool down (from -4 to -10°C/second), assists in forming a fine grain structure to increase solder joint fatigue resistance.
This Application Note 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.