• Excellent wetting on a variety of surface finishes
• Fewer voids, reduced size of largest void, overall minimizing voiding
• Exceptional printing process window (RtP, stencil life, slump resistance)
• Maintains tackiness over time
Indium Corporation manufactures low oxide spherical powder composed of eutectic SnPb and SnPbAg in the industry standard type 3 mesh size (J-STD-006). Other non-standard mesh sizes are available upon request. The weight ratio of the flux/vehicle to the solder powder is referred to as the metal load and is typically in the range of 80–92% for standard alloy compositions.
Alloy Metal Loading (% by weight)
Name Composition T3 Printing T4 Printing
Storage and Handling
Refrigerated storage will prolong the shelf life of solder paste. The shelf life of Indium6.4 is 6 months when stored at <10°C. When storing solder paste contained in syringes and
cartridges, the packages should be stored with tip down. Solder paste should be allowed to reach ambient working temperature prior to use and before opening the jar. Ideally, the working environment would be 23–28°C and 40–60% RH. Generally, paste should be removed from refrigeration at least two hours prior to 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.achieve the desired viscosity.
Material Safety Data Sheets The MSDS for this product can be found online at http://www.indium.com/techlibrary/msds.php
The high tack value of Indium6.4 assures consistent component holding power. It allows high speed component placement operation, including use of tall components.
Sn 62 Sn62/Pb36/Ag2
Indalloy® 100 Sn62.6/Pb37/Ag0.4
Tack remains adequate for over 8 hours over a wide humidity range.
Standard packaging for stencil printing applications includes wide-mouth 500g jars and 700g cartridges. For dispensing applications, 10cc and 30cc syringes are standard. Other packaging options may be available upon request.
J-STD TESTS & RESULTS
• Flux Type Classification ORH1
• SIR Pass
• Wetting Test Pass
• Typical Solder Paste Viscosity
(Sn63, 90.0%, Type 3
Malcom (10 rpm) 900 poise
• Typical Tackiness 30g
• Slump Test Pass
• Solder Ball Test Pass
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.
The following are general recommendations for stencil printer optimization for Indium6.4. Adjustments may be necessary based on specific process requirements:
• Solder Paste Bead Size: 20–25mm diameter
• Print Speed: 25–150mm/sec
• Squeegee Pressure: 0.018–0.027kg/mm of blade length
• Underside Stencil Wipe: Once every 10–25 prints
or as necessary (dry wipe recommended)
• Solder Paste Stencil Life: >8 hrs. @ 40 to at least
60% R.H. & 22–28°C
Indium6.4 exhibits excellent wetting on a wide variety of surface finishes, such as immersion tin, immersion silver, nickel-gold, palladium, alloy 42, HASL, and OSP, under both air and nitrogen reflow atmosphere. The solder joints yielded are very shiny and smooth, including those of ultra-fine-pitch components. Indium6.4 has ultra-low voiding performance. Minimal voiding can be achieved with optimal process conditions.
Residue Cleaning: Indium6.4 flux residue is cleanable up to at least 72 hours after reflow and is best cleaned using DI water with a spray pressure of at least 40 psi and a temperature of at least 40°C. These parameters are a function of board complexity and cleaner efficency.
This is best performed using an automated stencil cleaning system for both stencil and misprint cleaning to prevent extraneous solder particles. Most commercially available stencil cleaners and isopropyl alcohol (IPA) work well.
This profile is designed for use with Sn63/Pb37 and Sn62/Pb36/Ag2 and can serve as a general guideline in establishing a reflow profile for use with other alloys. Adjustments to this profile may be necessary based on specific process requirements.
A linear ramp rate of 0.5°– 2.0°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 unnecessary depletion of fluxing capacity when using higher temperature alloys. A profile with an extended soak above 150°C can be implemented to reduce void formation and minimize tombstoning when required.
A peak temperature of 25°– 45°C (215°C shown) above the melting point 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 is greater than the recommended 30–90 seconds, flux charring, excessive intermetallic formation, and damage to the board and components can occur.
A rapid cool down of <4°C/second is desired to form a fine grain structure. Slow cooling will form a large grain structure, which typically exhibits poor fatigue resistance. If excessive cooling of >4°C/second is used, both the components and the solder joint can be stressed due to a high CTE mismatch.