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.
Just last month at the IMAPS show in Boston, Sze Pei Lim and I had the opportunity to chat with Francoise von Trapp from 3D InCites to discuss materials ai...
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Die-attach for high-power devices, such as IGBT and emerging wide bandgap semiconductors, is facing increasing challenges, including service temperature, power density, and reliability. Conventional high-lead solder materials are reaching their performance limitations. Indium Corporation has developed, and is developing, novel lead-free die-attach materials to meet today’s and tomorrow’s challenges.
The term die-attach is reserved for processes where the face of a die is attached to a substrate by a single joint. The joint may be polymer (adhesive), metal-filled polymer, or in the form of solder derived from a preform or solder paste.
Gold Solders
Indium Corporation is a leading gold solder innovator for medical, aerospace, optoelectronics, and automotive applications. Gold-based alloys offer strong bond strength, excellent corrosion and oxidation resistance, and good thermal and electrical transfer at the braze joint. Our gold solder suite includes wire, paste, preforms, and ribbon. We manufacture these products with advanced technology to ensure quality, as well as push the boundaries of precision preforms.
Indium Corporation provides high-performance precision gold preforms. Our manufacturing engineers have developed advanced gold and braze preform manufacturing technology to produce “best in class” precision preforms. These high-quality preforms redefine the boundaries of what’s capable in regard to complex designs and aggressive aspect ratios. Eutectic and off-eutectic options are available in preforms and ribbon.
Indium Corporation’s AuLTRA™ ThInFORMS™ are an excellent choice for die-attach applications. By using a preform with a thickness of 0.00035", the BLT is reduced and thermal transfer from the die to the substrate is improved, increasing the operational performance and efficiency of high-output lasers. Packaging designed for automated assembly of these preforms ensures repeatable success in a production process.
Indium Corporation developed our AuLTRA™-Fine Ribbon, Indalloy®182 fine-grade precision ribbon, for high-volume, fully automated laser diode assembly processes. For these auto-feed systems, the precision and quality of the ribbon and spooling is of the utmost importance along with long, continuous lengths. These features help minimize production downtime and facilitate an efficient, high-throughput process resulting in a high-quality end product and low cost of ownership.
Indium Corporation’s Off-Eutectic AuSn Alloys are an excellent choice for die-attach applications. Using an AuSn preform with a lower gold content allows for absorption of some of a die’s thick gold plating, finalizing the solder joint at a composition of 80Au/20Sn, which has high tensile (joint) strength properties. Packaging designed for automated assembly of these preforms ensures repeatable success in a production process.
Indium Corporation’s QuickSinter® silver sintering pastes are another lead-free option for die-attach applications. They are high metal-loading materials designed to fit easily into a dispense process with no change of deposition equipment. The pastes can also use fast "reflow-like" (RFL) sintering processes to form strong joints on many standard leadframe, DBC, and IPM pad finishes, and will bond strongly to die with Ag, Au, or Cu surfaces.
Indium Corporation’s InFORMS®ESM02 is a reinforced solder fabrication that produces a high-reliability solder joint with increased thermal and mechanical performance. The matrixed solder composite is specifically designed to produce consistent bondline thickness for die-level attach applications.
Until recently, InFORMS® technology was only applied at the baseplate level. New production capabilities have expanded its use to the die-level with a bondline of 50μm.
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). We have a portfolio of solder pastes to cater to different process requirements.
Indium Corporation’s “Power-Safe” NC-SMQ75 is the only solder paste suitable for use in non-cleaned clip-bonded applications in power semiconductor die-attach assemblies. 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.
Features:
Superior wetting capabilities compared to most low-residue formulations
Alpha emission can disrupt sensitive electronic components, causing concern in high-reliability devices. One source of alpha emission is the solder that is used to form interconnections between the substrate and chip.
Indium Corporation’s low-alpha range of high-Pb solder pastes, with alpha emission less than 0.01cph/cm2, is proven to reduce gate oxide damage and enhance long-term reliability, especially for high-power devices. It is available with common high-Pb alloys with existing chemistries.
Robust Tacking Agent for Power Electronics Assembly
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InTACK™ is a no-clean, no-residue, halogen-free material designed to affix solder preforms, chips, or dies in position after placement to prevent skewing and misalignment during power module manufacturing. It provides a strong bond and extended working time, maintaining its tacking properties throughout the assembly process and up to the final stage of the reflow cycle. Designed specifically for no-flux reflow with formic acid, InTACK™ results in a residue-free assembly for high soldering quality without any additional post-process cleaning steps. When applied with InFORMS® solder preforms, InTACK™ offers a complementary solution to improve reliability for power module soldering.
Maintains precise assembly alignment
Compatible with solder preforms, dies, and power module components
Indium Corporation is a leading alloy innovator for electronics assembly. When even 10 ppm of contamination can cause process and application failures—quality counts. We cast our alloys, which enables us to closely control the process from start to finish and ensure purity. With more than 220 alloys available, we have alloy solutions for temperatures up to 1100°C to meet the requirements of different die-attach applications.
