Microstructures were formed on low temperature co-fired ceramic (LTCC) green substrates with high fidelity using micro embossing. The impact of embossing temperature and pattern density against the embossed profiles was investigated. The increase in pattern density resulted in a macro deformation in addition to embossed micro-depth. The macro deformation can be decreased by careful management of pattern density as well as pressure ramp and temperature ramp. The embossed ceramic green substrates were debinded and co-fired with a supplier-recommended process; the dimension shrinkage of embossed channels after co-firing ranges from 20 to 22% in depth and from 10 to 13% in width. The achievements of this investigation demonstrated that micro embossing is a promising process for fabricating ceramic-based microstructures and devices, including embedded cavities and channels.

Low temperature cofired ceramic substrates are becoming increasingly attractive for high density electric circuits and microsystems. Embedded micro patterns such as channels and cavities in ceramic substrates are indispensable for circuit cooling and media transportation. One of process challenges is how to make these embedded micro channels and cavities, which would be collapsed or deformed under conventional lamination. This paper reports on a novel solvent-assisted lamination that could provide low pressure and room temperature lamination of ceramic green tapes. The solvent used in this study was turpentine oil, which demonstrated a proper capability of dissolving polymeric additives on surface of green tapes without obviously changing the distribution of ceramic particles. Procedures for forming embedded micro channels in ceramic green substrates include micro embossing to create open channels, coating of turpentine solvent, followed by low pressure and room temperature lamination. Embedded micro channels with channel width ranging from 25 to 1,000 lm were obtained in ceramic green substrates; Depths of embedded channels shrank by 3-12% versus embossed depths due to turpentine-assisted lamination. The ceramic green substrates with embedded channels were then sintered under a standard cofiring process.

Multi-layered ceramic substrates with embedded micro patterns are becoming increasingly important, for example, in harsh environment electronics, enabling microsystems and microfluidic devices. Fabrication of these embedded micro patterns, such as micro channels, cavities and vias, is a challenge. This study focuses on the process aspects of patterning micro features on low temperature co-firable ceramic (LTCC) green substrates using micro hot embossing. Green ceramic tapes that possessed near-zero shrinkage in the x-y plane were used, six layers of which were stacked and laminated as a substrate. The process parameters that impact on the embossing fidelity were investigated and optimized in this study. Micro features with channel-width as small as several micrometers were formed on green ceramic substrates. The dynamic thermo-mechanical analysis indicated that extending the holding time at a certain temperature range would harden the substrates with little effect on improving the embossing fidelity. Ceramic substrates with embossed micro patterns were obtained after co-firing; the shrinkage ratios of the embossed depth and channel-width were 8-15 and 12-17%, respectively. The changes of pitches between two embossed channels were within ±1.0% due to the interlocking effect of the ceramic tapes.

PurposeThe purpose of this paper is to present the results of experiments performed to attach silicon dies (chips) to low‐temperature co‐fired ceramic (LTCC) substrates with Ag or AgPd pads using SnAgCu or SnPb solder and the results of the characterization of the solder joints.Design/methodology/approachLTCC substrates were fabricated by stacking and laminating four green tapes with the top layer screen‐printed with Ag or AgPd paste to form pads. Silicon die sizes of 1 × 1 mm and 2 × 2 mm with electroless nickel immersion gold plated were soldered to 2 × 2 mm pads on the LTCC substrates using SnPb or SnAgCu solder. The solder joints were then characterized using X‐ray, die shear, energy dispersive X‐ray and scanning electron microscopy techniques.FindingsThe joints made by AgPd pads with SnAgCu solder provided the best results with the highest shear strength having strong interfaces in the joints. However, the joints of Ag pads with SnPb solder did not provide high‐shear strength.Originality/valueThe findings provide certain guidelines to implement LTCC applications. AgPd pads with SnAgCu solder can be considered for applications where small silicon dies need to be attached to LTCC substrates. However, Ag pads with SnAgCu solder can be considered for lead‐free solder applications.

No abstract