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Solder and Adhesive Free Chip Assembly Using Elastic Chip Sockets: Concept, Manufacture and Preliminary Investigation
2004 (English)In: Proceedings of 2004 International IEEE Conference on the Asian Green Electronics (AGEC), 2004, 12-17 p.Conference paper, Published paper (Refereed)
Abstract [en]

Flip Chip connections enormously reduces the amount of solder as compared to mounting packaged devices, apart from also offering superior high frequency properties and placement density. However, when assembling chips to substrates having different thermal expansion coefficient, the solder balls are exposed to strain, the more so the denser the connections (and consequently smaller balls), and the higher the power densities, resulting in wider temperature cycles. This will usually result in loss of contact reliability. Using other materials than solder or using underfills may partially improve the situation, but causes other problems. In order to test another concept maintaining or exceeding the excellent HF and density properties of conventional Flip Chip, while practically eliminating the thermal mismatch problems and providing effortless chip replacement, the Elastic Chip Socket was developed. Silicone elastomer was molded in a precision mold made using anisotropic etching of Si. These structures were subsequently metallized and the metal patterned using electro plated resist. So far functional chip sockets with pin densities of 45 000 pins per cm2 (22 500 simultaneously functional connections to a 7 × 7 mm die) and more have been achieved which endure multiple repeated matings and quick temperature cycling between - 40°C and + 90°C. The following is a summary of the group's achievement this far, Oct. 2003.

Place, publisher, year, edition, pages
2004. 12-17 p.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-5464DOI: 10.1109/AGEC.2004.1290858ISBN: 078038203X (print)OAI: oai:DiVA.org:kth-5464DiVA: diva2:9837
Conference
2004 International IEEE Conference on Asian Green Electronics (AGEC); Hong Kong; 5 January 2004 through 9 January 2004
Note
QC 20110114Available from: 2006-03-14 Created: 2006-03-14 Last updated: 2011-01-14Bibliographically approved
In thesis
1. Manufacture and characterization of elastic interconnection microstructures in silicone elastomer
Open this publication in new window or tab >>Manufacture and characterization of elastic interconnection microstructures in silicone elastomer
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The subject of this thesis is a new chip to substrate interconnection technique using self-aligning elastic chip sockets. This work was focused on the technology steps which are necessary to fulfill in order to realize the suggested technique. Elastic chip sockets offer a solution for several assembly and packaging challenges, such a thermo-mechanical mismatch, effortless rework, environmental compatibility, high interconnection density, high frequency signal integrity, etc.

Two of the most challenging technology aspects, metallization and etching of the silicone elastomer were studied, but also, air bubble free casting of the silicone elastomer was taken into consideration. Elastic chip sockets and single elastic micro-bump contacts of different shapes and sizes were manufactured and characterized.

The contact resistance measurements revealed that the elastic micro-bump contacts manufactured by using the developed methods require less than one tenth of the contact force to achieve the same low contact resistance as compared to commercial elastic interconnection structures.

The analysis and measurements of the high frequency properties of the elastic micro-bump structures have shown that they can operate up to several tens of GHz without a serious degradation of the signal quality.

The same methods were applied to manufacture very high density contact area array (approximately 80000 connections/cm2), which until now was achieved only using so called chip-first techniques.

The low contact resistance, the absence of environmentally harmful materials, no need of soldering, easy rework as well as capability of very high interconnecting density and very high frequency compatibility, indicates a high potential of this technique for assembly and packaging.

Moreover, the presented technology of the silicone elastomer micromachining (metallization and RIE in particular) can be used for manufacturing of other microstructures, like chemical or biological micro reactors.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. xiv, 47 p.
Series
Trita-EKT, ISSN 1650-8599 ; 2006:1
Keyword
silicone elastomer, packaging, assembly, elastic interconnection, chip socket, metallization, RIE of silicone elastomer
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-3877 (URN)
Public defence
2006-03-23, Sal Q221, Mittuniversitet, Östersund, 13:00
Opponent
Supervisors
Note
QC 20110114Available from: 2006-03-14 Created: 2006-03-14 Last updated: 2011-01-14Bibliographically approved

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