Plating dies and/or substrates with pure gold works well to prevent the components from oxidizing, but can lead to undesirable gold-rich solder joints. Using an off-eutectic AuSn alloy as the solder material accommodates for these thick gold metallizations, allowing for the exact adjustment of the final solder joint composition to guarantee strong solder joints in die-attach applications.
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The joint may be of polymer (adhesive), metal-filled polymer, or in the form of solder derived from a preform or solder paste. (Die-attach wire may also be available.)
Die-Attach Paste
Although there are four major processes for die-attach, solder-based processes are still the most popular, as they provide high reliability with ease of processing. Indium Corporation’s die-attach solder paste is typically a dispensable, high melting-point solder paste, which is reflowed in forming gas (H2N2 mix).
Key Performance Needs
Low voiding in reflow
Long dispense life
No tailing
No separation
Bubble-free packaging
Residue-free cleaning or residue compatible with overmolding process
“Power-Safe” NC-SMQ®75 Die-Attach Solder Paste
NC-SMQ®75 is the only solder paste suitable for use in non-cleaned clip-bonded applications in power semiconductor die-attach assemblies. It has:
Superior wetting capabilities compared to most low residue formulations
Indium Corporation’s “Power-Safe” NC-SMQ75 is an ultra-low residue, halogen-free, die-attach solder paste that leaves a completely benign, almost undetectable residue of approximately 0.4 weight percent of paste.
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NC-SMQ75 is the only solder paste suitable for use in non-cleaned clip bonded applications in power semiconductor die-attach assemblies.
It is designed for reflow in a nitrogen or forming gas atmosphere of 100 ppm oxygen or less and can survive the high temperatures associated with both high-lead (Pb) and gold-tin alloy reflow.
Bellcore and J-STD Tests & Results
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Test
Result
J-STD-004 (IPC-TM-650)
Flux Type Classification
ORL0
Presence of Halide Fluoride Spot Test
Pass
Elemental Analysis
Halide-Free
Post Reflow Flux Residue (ICA Test)
0.4% of solder paste
Corrosion
Pass
SIR (Post Clean)
Pass
Acid Value (Typical)
31.5
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Test
Result
J-STD-005 (IPC-TM-650)
Typical Solder Paste Viscosity (Pb92.5/Sn5/Ag2.5. Type 3. 88%)
Brookfield (TF 5 rpm)
230 kcps
Brookfield (R7 10 rpm)
170 kcps
Slump Test
Pass
Solder Ball Test
Pass
Wetting Test
Pass
Standard Metal Load
88%
All information is for reference only. Not to be used as incoming product specifications.
Features:
Ultra-low post-reflow residue <0.5%w/w of solder paste
“Power-Safe” residue compatible with overmolding compounds without delamination
