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Elastomer Chip Sockets for Reduced Thermal Mismatch Problems and Effortless Chip Replacement, Preliminary Investigations
2003 (English)In: IEEE Transactions on Advanced Packaging, ISSN 1521-3323, E-ISSN 1557-9980, Vol. 26, no 1, 33-40 p.Article in journal (Refereed) Published
Abstract [en]

To avoid the problem with thermo-mechanical stress induced fatigue using conventional flip-chip mounting of bare chips, an elastic chip socket has been developed.

The socket is made by casting silicone elastomer into micro structured silicon molds to form micro bump arrays. After the elastomer is cured and released from the mold, a metal layer is deposited and patterned.

A chip is placed in the socket utilizing guiding structures for chip self alignment. The chip is then held in place by a spring loaded back-plate which can also serve as a heat sink for highly effective chip cooling. Since no adhesives, underfills or solders are used, the rework process becomes very simple and it can also be repeated many times for-the same socket.

Initial contact resistance and thermo-mechanical robustness measurements indicates that this type of sockets could work as a superior replacement for conventional flip-chip technologies in many applications. The particular design of the contact bumps results in metal structures that resemble (although up side down) and are scalable as those in the Chip-First technology. Preliminary thermal shock experiments from room temperature to liquid nitrogen and back show good survival. Thus, this new chip interconnect method indicates the possibility of getting the advantages of the Chip-First technology while eliminating the demand of placing the chip first. The concept will work for chips with rim positioned pads as well as for high density area arrays.

Place, publisher, year, edition, pages
2003. Vol. 26, no 1, 33-40 p.
Keyword [en]
chip-first; chip socket; flip chip; multi-chip modules; packaging; silicone elastomer; thermal fatigue; thermal stress
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-5461DOI: 10.1109/TADVP.2003.811362ISI: 000182870300005OAI: oai:DiVA.org:kth-5461DiVA: diva2:9834
Note
QC 20110114Available from: 2006-03-14 Created: 2006-03-14 Last updated: 2017-11-21Bibliographically 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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