382 IEEE TRANSACTIONS ON ADVANCED PACKAGING, VOL. 29, NO. 3, AUGUST 2006 Novel Microcontacts in Microwave Chip Carriers Developed by UV-Liga Process Part II Radosvet Arnaudov, Member, IEEE, Bojidar Avdjiiski, Aleksandar Kostov, Valentin Videkov, Svetozar Andreev, and Nikola Yordanov Abstract—This paper presents the design and development of novel type microcontacts in monolithic microwave integrated circuit (MMIC) chip-carriers to printed circuit board (PCB) assembly. Several new concepts of microcontacts for packaging solutions of microwave and millimeter-wave MMIC are depicted. Simulation and vector network analyzer (VNA) measurement results for these microcontact transitions are discussed. The re- sults show that the electrical parameters are highly dependent on the transition dimensions and substrate features. These contacts are based on male stud (bump) and female (ring) concept. When mating each other, there are clips effect and self-alignment fea- tures. Special attention is paid to the shape of the microcontacts in order to facilitate assembly and strengthen the connection. Equivalent electrical circuit is proposed for PSPICE simulation of the dc contact resistance. Finally, the article discusses the technological implementation of the proposed new microcontact stud-ring through low-cost ultraviolet electroplating, lithography, and molding (UV-LIGA) process and the regime influence on the shape, geometry, and mating capabilities. Results from mechanical pull and adhesion tests are also discussed. Index Terms—Clips mating, microcontacts, microwave, mono- lithic microwave integrated circuit (MMIC), ring, solderless as- sembly, stud, ultraviolet electroplating, lithography, and molding (UV-LIGA). I. INTRODUCTION T HE continued growth of personal communications with wireless applications has generated a great demand for portable and highly integrated components and subsystems. As a consequence, these applications challenge electronics packaging technologies to integrate smaller, lighter, high-den- sity, mixed integrated circuits, reproducible, and low-cost packages and modules [1]. The demand for size reduction of the transmit/receive modules or even integration of antenna and transmit/receive module becomes more and more important [2]. By integrating several functions in a single multifunction module, the size of a transmit/receive module can be consid- erably reduced. However, the influence of the microcontacts in the packages for microwave applications on the electrical performance of the devices is still object of investigation. Microcontact transition has become a promising technique in Manuscript received June 21, 2005; revised November 4, 2005. This work was supported by RaySat BG (formerly SkyGate BG) under Contract 2513- 3/21.04.2000 “Development of Galvanic and Combined Micro-Contacts for Mi- crowave Chip-Carriers.” R. Arnaudov, B. Avdjiiski, and A. Kostov are with RaySat BG, 1700 Sofia, Bulgaria (e-mail: arnaudov-r@raysat.bg). V. Videkov, S. Andreev, and N. Yordanov are with the Department of Microelectronics, Technical University Sofia, 1000 Sofia, Bulgaria (e-mail: videkov@tu-sofia.bg). Digital Object Identifier 10.1109/TADVP.2006.875411 the microwave and millimeter wave frequencies, due to the features of short and stable electrical interconnection, low cost, and high reliability. This paper presents the design, three-dimensional (3-D) elec- tromagnetic simulations, vector network analyzer (VNA) mea- surements, and fabrication of stud and ring microwave micro- contacts in chip carrier to printed circuit board (PCB) assembly. The unique features of this novelty concept are the self-align- ment effect, clips mating of male stud to female ring—socket, and even solderless assembly of the interconnection. It was sug- gested that the height of the microcontacts be kept comparable to their - dimensions in order to ease assembly and enhance reliability and strength of the connection. This usually causes great concern in the fabrication and the inevitable choice of ul- traviolet electroplating, lithography, and molding (UV-LIGA) process. A lot of the basic concepts and microcontact features were discussed in [3]. II. OBJECTIVES The reported work was aimed at the following: — investigating the electrical characteristics of microcon- tacts of type galvanic studs and rings in order to evaluate their applicability for microwave chip carriers’ assembly; — finding the optimal shape and dimensions of the micro- contacts; — experimenting technologically some new concepts of mi- crocontacts for low-cost assembling of microwave pack- ages and multichip modules (MCMs). A. Background A significant research on new packaging technologies for high-frequency radio frequency (RF) and millimeter-wave applications is conducted. In [4], the authors report that the Micro Substrates Corporation (MSC) developed new ball grid array (BGA) surface-mount packaging technology for high-fre- quency RF and millimeter-wave applications named VIA/PAK. The reported VBGA package demonstrated good insertion and return loss characteristics in the dc to 31.5-GHz range. In [4], a microwave multilayer plastic-based multichip module is described. A vertical feed-through interconnect which consists of embedded copper wires in the plastic has been developed to transport RF/microwave and dc signals from the first to the second packaging level. So, the plastic modules could be con- figured in a surface mount topology that can be integrated with FR4 boards using BGA. Experimental verification of simulated crosstalk and impedance control of microstrip lines through 1521-3323/$20.00 © 2006 IEEE