Indium Corporation

The flip-chip process involves taking the singulated die from a wafer mounted on a wafer dicing tape, inverting ("flipping") them and placing them onto a substrate. The substrate may be a printed circuit board, a ceramic substrate, or (in the case of 2.5D and 3D assembly) an interposer. Copper pillarsolder microbumps are emerging as a standard flip-chip solder bump replacement in many parts of the semiconductor assembly industry, from standard chip-attach to power devices using flip-chip on leadframe as assembly technologies. For logic and similar devices, substrate metallization (landing pad) technology has also shifted from solder-on-pad (SoP), manufactured from printed and reflowed and cleaned solder paste, to individual solder balls. The technology is now moving to simple organic solderability protectant (OSP) on copper. Water-soluble fluxes, which may be applied by dipping or spraying, have long been used in flip-chip assembly, but their long history of utility is coming to a close as a number of factors makes the move to no-clean inevitable in the high-volume sub-130micron copper pillar era. The use of copper pillar instead of solder bumps has meant that chip-substrate clearances and finer pitches do not necessarily move in lock-step with each other. However, copper pillar heights of 40-60 microns (and even shorter than this in the near future) combined with fine pitch, makes cleaning extremely complex. Aqueous (water-based) cleaning becomes more complex with fine pitch flip-chip attach as it becomes increasingly difficult to get the cleaning solution under the chip to dissolve the residues, and then to carry the residue-containing solution out from under the chip. A recent emerging failure mode caused by cleaning involves solder joint damage during aqueous jet impingement. This failure mode is believed to be driven by a combination of: very small diameter microbumps; the move from hemispherical to very thin solder microbumps on copper pillar (reduced joint compliance); and low CTE, low-cost, and low layer count (thinned) substrates. In these circumstances, a move towards an ultra-low residue no-clean flux is inevitable, although new failure modes continue to appear, being driven by the smaller dimensions. For this reason, Indium Corporation has introduced a new ultra-low (ULR) flux called NC-26-A for both current and emerging applications.

Indium Corporation® manufactures electroplating anodes in several forms: With an embedded hook Bulk indium metal anodes Ingots Indium foil Indium ribbon Anodes with embedded hooks are made from Monel® alloy. They are shaped dimensionally true so the anode rod will hang straight. Anodes are available with 7” or 5” hooks.

Epoxy fluxes are often used in no-clean SMT component attach applications. The solder bumps on wafer level CSP, micro BGA or BGA packages are dipped in epoxy fluxes, or the flux is applied to the substrate via a jetting process. The assembly is then reflowed, and the epoxy flux acts to both clean up the solder joints before reflow, and to reinforce the final joint from the cured polymer.

• FluxNC-10HF
• IPC ClassificationROL0
• Substrate FinishesAu, Ag, Pd, Pt, Cu, Ni, HASL, ENIG, Sn
• Reliability J-STD-004Pass

Indium Corporation is a leading joining and bonding materials innovator for medical, aerospace, optoelectronics, and automotive applications. When even 10 ppm of contamination can cause process and application failures – quality counts. Indium Corporation casts our alloys, which enables us to closely control the process from start to finish and ensure purity. High-Temperature Solder and Braze Materials Deliver: Highest tensile strength of any solder High melting point is compatible with subsequent reflow processes Pb-free and RoHS compliant Superior thermal conductivity Resistance to corrosion Superior thermal fatigue resistance Good joint strength Excellent wetting properties Resistance to oxidation

Indium-electroplated films have many industrial applications that take advantage of the unique physical and chemical properties of the indium metal, such as its low melting point, low vapor pressure, inherent softness and malleability, cold welding properties, anti-friction properties, and alloy hardening properties. Indium electroplating applications include surface preparation, decorative finishing on metals and plastics, sealing, aircraft bearings, and electrical interconnects in microelectronic devices. Our complete set of electroplating products includes all materials needed for indium electroplating processes: