60-GHz Band Copper Ball Vertical Interconnection for MMW 3-D System-in-Package Front-End Modules

Satoshi YOSHIDA  Shoichi TANIFUJI  Suguru KAMEDA  Noriharu SUEMATSU  Tadashi TAKAGI  Kazuo TSUBOUCHI  

IEICE TRANSACTIONS on Electronics   Vol.E95-C   No.7   pp.1276-1284
Publication Date: 2012/07/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E95.C.1276
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Microwaves, Millimeter-Waves
millimeter-wave,  60-GHz band,  system-in-package,  vertical interconnection,  copper balls,  WPAN,  

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In order to realize millimeter-wave (MMW) 3-D system-in-package (SiP) front-end modules, we propose a 60-GHz band copper ball vertical interconnection structure, which interconnects between vertically stacked substrates. The structure enables ICs to be placed between the vertically stacked substrates. Since the diameter of the copper balls must exceed the thickness of the ICs, the distance between the substrates in the modules is larger than that of the flip-chip interconnection widely used in the MMW-band. Therefore, the conventional flip-chip interconnection does not scale for the interconnection between the substrates in MMW 3-D SiP front-end modules. The layout of grounded copper balls and the patterns of inner ground layers in the upper/lower substrates are designed using 3-D electromagnetic field simulation. The designed structure allows less than 1 dB transmission loss up to 71.1 GHz, compared with a through transmission line. The result is verified with fabrication and measurement and confirms the feasibility of MMW 3-D SiP front-end modules.