倒装焊对探测器频响特性影响的理论分析及工艺优化

针对光探测器在倒装焊过程中频响性能恶化的问题,建立等效电路模型分析出其原因,并通过优化倒装焊工艺条件予以有效解决。该电路模型包括探测器芯片、过渡热沉和倒装焊环节三个部分。基于倒装焊后探测器的S11参数和频响曲线提取出倒装焊环节特征参数,确认焊点接触电阻过大是引起探测器频响下降的主要原因。通过优化倒装焊工艺条件,有效减小了焊点接触电阻,基本消除了倒装焊对探测器频响特性的影响。     

Experimental validation of GaN HEMTs thermal management by using photocurrent measurements

A major limitation in the performances of AlGaN/GaN high-electron mobility transistors (HEMTs) is due to self heating effects, connected to the efficiency of heat removal from the device. In this paper, we present a new experimental investigation on the thermal handling capabilities of AlGaN/GaN HEMTs, with conventional and flip-chip bonding. Efficient photocurrent measurements were performed in order to extract directly the channel temperature for all the device configurations. We were able to measure devices realized on sapphire substrate both with conventional and flip-chip bonding, and to compare them with devices on SiC substrate with conventional bonding, demonstrating that flip-chip bonding allows to achieve almost the same results that SiC substrate. Measured results are in good agreement with the presented simulation data.     

The application of flip-chip bonding interconnection technique on the module assembly of 10 Gbps laser diode

Flip chip bonding technique using Pb/In solder bumps was applied to packaging of a 10 Gbps laser diode (LD) submodule for high speed optical communication systems. The effect of the flip-chip bonding interconnection technique instead of conventional wire bonding was investigated for high speed broad band devices. The broad band performance of 10 Gbps LD submodule was simulated using SPICE S/W and compared with experimental results. In this simulation, the 10 Gbps LD was modeled in a parallel RC circuit. The values of R and C used for the equivalent circuit were 5ω and 1 pF, respectively. The LD was placed in series with a 18ω thin film resistor to prevent the impedance mismatch between the LD and a 25ω transmission line. The dependence of parasitic parameters on the small signal modulation bandwidth and the scattering parameters of the LD submodule was investigated and analyzed up to 20 GHz. A small signal modulation bandwidth of 14 GHz at 10 mA dc bias current and the clean modulation response up to 20 GHz were found for the flip-chip bonded submodule. The bandwidth of flip-chip bonded 10 Gbps LD submodule is wider than that of the wire-bonded LD submodule by a difference of 3.8 GHz.     

A new flip-chip bonding technique using micromachined conductivepolymer bumps

Using micromachining techniques with thick photoresists, a new conductive polymer flip-chip bonding technique that achieves both a low processing temperature and a high bumping alignment resolution has been developed in this work. By the use of UV-based photolithography with thick photoresists, molds for the flip-chip bumps have been patterned, filled with conductive polymers, and then removed, leaving molded conductive polymer bumps. After flip-chip bonding with the bumps, the contact resistances measured for 25 μm-high bumps with 300 μm×300 μm area and 400 μm×400 μm area were 35 mΩ and 12 mΩ respectively. The conductive polymer flip-chip bonding technique developed in this work shows a very low contact resistance, simple processing steps, a high bumping alignment resolution (<±5 μm), and a lower bonding temperature (~170°C). This new bonding technique has high potential to replace conventional flip-chip bonding technique for sensor and actuator systems, bio/chemical μ-TAS, optical MEMS, OE-MCM's, and electronic system applications     

A novel flip-chip interconnection technique using solder bumps forhigh-speed photoreceivers

A flip-chip interconnection technique using small solder bumps instead of conventional wire bonding for high-speed broadband photoreceivers is described. The technique achieves interconnection with low parasitic elements, no damage to devices, and easy assembly. A photoreceiver composed of a broadband p-i-n photodiode and a laser-speed GaAS metal-semiconductor field-effect transistor (MESFET) preamplifier connected using solder bumps that are about 26 μm in diameter, with a frequency response of over 22 GHz at 1.55 μm, is demonstrated. This confirms the effectiveness of the solder bump interconnection technique for future high-speed broadband optical modules     

Optoelectronic and microwave transmission characteristics of indium solder bumps for low-temperature flip-chip applications

This paper describes low-temperature flip-chip bonding for both optical interconnect and microwave applications. Vertical-cavity surface-emitting laser (VCSEL) arrays were flip-chip bonded onto a fused silica substrate to investigate the optoelectronic characteristics. To achieve low-temperature flip-chip bonding, indium solder bumps were used, which had a low melting temperature of 156.7/spl deg/C. The current-voltage (I-V) and light-current (L-I) characteristics of the flip-chip bonded VCSEL arrays were improved by Ag coating on the indium bump. The I-V and L-I curves indicate that optical and electrical performances of Ag-coated indium bumps are superior to those of uncoated indium solder bumps. The microwave characteristics of the solder bumps were investigated by using a flip-chip-bonded coplanar waveguide (CPW) structure and by measuring the scattering parameter with an on-wafer probe station for the frequency range up to 40 GHz. The indium solder bumps, either with or without the Ag coating, provided good microwave characteristics and retained the original characteristic of the CPW signal lines without degradation of the insertion and return losses by the solder bumps.     

光发射模块中激光器与光纤的无源耦合

对光电发射模块中激光器与光纤的无源耦合作了研究.利用成熟的100mm硅工艺研制成功了无源耦合用硅基平台,并可以批量生产.在此基础上利用倒装工艺实现了激光器与单模光纤的无源耦合,出纤光功率达到了毫瓦级,且经过37次高低温冲击性能不变.     

Hybrid integration of surface-emitting microlaser chip and planaroptics substrate for interconnection applications

The bonding of a monolithic array of surface-emitting microlasers onto a glass substrate that contains a matching array of microlenses and mirrors is reported. The bonding was achieved by flip-chip solder bump bonding using indium as the solder material. The alignment precision is within ±2 μm. The optical substrate provides a simple interconnection scheme that routes the light from each laser to well defined output positions     

The design and assembly of surface-micromachined optical switch for optical add/drop multiplexer application

An assembly process including: flip-chip bonding, microelectromechanical (MEMS) structure release, and atomic layer deposition (ALD) is proposed to integrate a surface micromachined optical switch for optical add/drop multiplexer (OADM) applications. In the current optical switch designs, pre-stressed beams were used to pop up the micromirror and an electrode (substrate) under the beams was designed to perform ON/OFF function of the optical switch. In order to achieve desired popped-up angle for precise optical switching, a flip-chip bonding technique is applied to a mechanical stopper with an accurate joint height that can be used to constrain the movement of the micromirror. A conformal thin layer of dielectric material (Al/sub 2/O/sub 3/) coated on the surfaces of device through an ALD coating process is used to improve vertical actuation force, as well as electrical isolation. Experiments indicate that the micromirrors fabricated by the present assembly process can achieve desired angle that meet the requirements of the proposed OADM configuration.     

Multichip Integration on a PLC Platform for 16 × 16 Optical Switch Module Using Passive Alignment Technique

We have integrated eight sets of four-channel semiconductor optical amplifier (SOA) array chips on a silica-based planar lightwave circuit (PLC) platform for 16 times 16 optical switch module by flip-chip bonding technique. To accurately bond eight sets of the arrayed SOA chips on a PLC platform, two methods of two-step assembly and one-step assembly were tried. Among the results of two assembly methods, one-step assembly was estimated to be desirable in respect of the horizontal and vertical bonding accuracy. The bonding accuracy was measured to be within 0.5 mum. Also, we demonstrated 16 times 16 optical switch module.     

凸点芯片倒装焊接技术

凸点芯片倒装焊接是一种具有发展潜力的芯片互连工艺技术。目前主要有C4、热超声和导电粘接剂等工艺方法,本文介绍了这三种工艺的技术特点、工艺流程及应用领域。     

New hybrid integrated laser diode-drivers using microsolder bumpbonding: SPICE simulation of high-speed modulation characteristics

This paper proposes two types of new hybrid integrated laser diode (LD)-drivers that use microsolder bump bonding instead of conventional wire bonding. In one, an LD and a driver are flip-chip bonded to each other; in the other, an LD and a driver are flip-chip bonded onto a substrate. Their performances are compared to those of a monolithic LD-driver and a conventional hybrid one using wire bonding by a simulation program with integrated circuit emphasis (SPICE) with particular emphasis on high-speed LD modulation. The nonreturn-to-zero (NRZ) eye patterns modulated at signal speeds up to 30 Gb/s by the new hybrid integrated LD-drivers were hardly inferior to those by the monolithic LD-driver, whereas those by conventional hybrid ones were greatly degraded over 10 Gb/s. The new hybrid integrated LD-drivers are a feasible alternative to monolithic ones for high-speed optical transmitters     

High-yield flip-chip bonding and packaging of low-threshold VCSEL arrays on sapphire substrates

Oxide-confined top-emitting 850 nm and bottom-emitting 980 nm vertical-cavity surface-emitting laser (VCSEL) 8/spl times/8 arrays were designed and fabricated for applications of optical interconnects. The arrays were flip-chip bonded onto sapphire substrates that contain complimentary metal-oxide-semiconductor (CMOS) driver and fan-out circuitries. The off-sited bonding contacts and minimized bonding force produced very high yield of the hybridization process without causing damage to the VCSEL mesas. The hybridized devices were further mounted either on printed circuit board (PCB) or in 68-pin pin-grid-array (PGA) packages. The transparent sapphire substrate allowed optical outputs from the top-emitting VCSEL arrays to transmit directly through without additional substrate removal procedure. Lasing thresholds below 250 /spl mu/A for 850 nm VCSELs and 800 /spl mu/A for 980 nm VCSEL were found at room temperature. The oxide confinement apertures of VCSELs were measured to be around 6 /spl mu/m in diameter. High-speed data transmission demonstrated a bandwidth of up to 1 Gbits/s per channel for these hybridized VCSEL transmitters.     

混成式焦平面阵列芯片倒装互连技术研究

介绍了为保证倒装焊接性能,设备所采取的措施。对比了不同形貌铟柱的优缺点,分析了互连可靠性与铟柱高度的关系,介绍了考核互连可靠性的方法。通过互连技术研究,我们实现了较高性能的倒装互连,互连条件选择温度在60℃-140℃范围,压力范围0．1克／铟柱-0．5克／铟柱。互连连通率〉99．9％,互连后的芯片组件在低温（77K）与常温（23℃）间不少于100次的反复冲击的情况下,测试接触性能及InSb二极管性能都无变化,满足了互连器件可靠性要求。     

Increasing the bonding strength of chips on flex substrates using thermosonic flip-chip bonding process with nonconductive paste

Thermosonic flip-chip bonding process with a nonconductive paste (NCP) was employed to improve the processability and bonding strength of the flip-chip onto flex substrates (FCOF). A non-conductive paste was deposited on the surface of the copper electrodes over the flex substrate, and a chip with eight gold bumps bonded onto the copper electrodes by the thermosonic flip-chip bonding process.For the chips and flex substrates assembly, ultrasonic power is important in the removal of some of the non-conductive paste on the surface of copper electrodes during thermosonic bonding. Accordingly, gold stud bumps in this study were directly bonded onto copper electrodes to form successful electrical paths between chips and the flex substrate. A particular ultrasonic power resulted in some metallurgical bonding between the gold bumps and the copper electrodes, increasing the bonding strength. The ultrasonic power was not only to remove the NCP from the copper electrodes, but also formed metallurgical bonds during the thermosonic flip-chip bonding process with NCP.In this study, the parameters of the bonding of chips onto flex substrates using thermosonic flip-chip bonding process with NCP were a bonding force of 4.9 N, a curing time of 40 s, a curing temperature of 140 °C and an ultrasonic power of 14.46 W. The processability and bonding strength of flip-chips on flex substrates using thermosonic bonding process with NCP was verified in this study. This process has great potential to be applied to the packaging of consumed electronic products.     

Thermal management of AlGaN-GaN HFETs on sapphire using flip-chip bonding with epoxy underfill

Self-heating imposes the major limitation on the output power of GaN-based HFETs on sapphire or SiC. SiC substrates allow for a simple device thermal management scheme; however, they are about a factor 20-100 higher in cost than sapphire. Sapphire substrates of diameters exceeding 4 in are easily available but the heat removal through the substrate is inefficient due to its low thermal conductivity. The authors demonstrate that the thermal impedance of GaN based HFETs over sapphire substrates can be significantly reduced by implementing flip-chip bonding with thermal conductive epoxy underfill. They also show that in sapphire-based flip-chip mounted devices the heat spread from the active region under the gate along the GaN buffer and the substrate is the key contributor to the overall thermal impedance.     

Gold Stud Bumps Flip-Chip Bonded onto Copper Electrodes with Titanium and Silver Layers

The purpose of this study was to develop the thermosonic flip-chip bonding process for gold stud bumps bonded onto copper electrodes on an alumina substrate. Copper electrodes were deposited with silver as the bonding layer and with titanium as the diffusion barrier layer. Deposition of these layers on copper electrodes improves the bonding quality between the gold stud bumps and copper electrodes. With appropriate bonding parameters, 100% bondability was achieved. Bonding strength between the gold stud bumps and copper electrodes was much higher than the value converted from the standards of the Joint Electron Device Engineering Council (JEDEC). The effects of process parameters, including bonding force, ultrasonic power, and bonding time, on bonding strength were also investigated. Experimental results indicate that bonding strength increased as bonding force and ultrasonic power increased and did not deteriorate after prolonged storage at elevated temperatures. Thus, the reliability of the high-temperature storage (HTS) test for gold stud bumps flip-chip bonded onto a silver bonding layer and titanium diffusion barrier layer is not a concern. Deposition of these two layers on copper electrodes is an effective and direct method for thermosonic flip-chip bonding of gold stud bumps to a substrate, and ensures excellent bond quality. Applications such as flip-chip bonding of chips with low pin counts or light-emitting diode (LED) packaging are appropriate.     

Packaging using microelectromechanical technologies and planarcomponents

A novel millimeter-wave packaging structure was developed in which a micromachined low-loss planar component and flip-chip devices were integrated on a silicon substrate. A low-loss planar filter was achieved on a 7-mm-square silicon substrate employing an inverted microstrip line and a unique resonator. High attenuation in the stopband was also obtained by introducing a pole control technique. Fabrication of a compact K-band receiver front-end incorporating a built-in filter was realized using multilayered benzocyclobutene (BCB) and flip-chip bonding techniques. Furthermore, we propose an alternative BCB suspended structure and demonstrate a planar antenna for Ka-band applications. These technologies bring to reality high-performance compact packaged systems in millimeter-wave region applications     

An Optical Interconnect Transceiver at 1550 nm Using Low-Voltage Electroabsorption Modulators Directly Integrated to CMOS

A low-voltage, 90-nm CMOS optical interconnect transceiver operating at 1550-nm optical wavelength is presented. This is the first demonstration of a novel optoelectronic modulator architecture (the quasi-waveguide angled-facet electroabsorption modulator) in a system. It features a simple electronic packaging via flip-chip bonding to silicon. Devices have a broad optical bandwidth, are arrayed two dimensionally, and feature surface normal, spatially separated, and misalignment-tolerant optical ports. The modulators are driven with a novel pulsed-cascode driver capable of supplying an output-voltage swing of 2 V (twice the nominal 1-V CMOS supply) without overstressing thin-oxide core CMOS devices. At the receiver side, a sensitivity of -15.2 dBm is obtained with an integrating/double-sampling front end. The transceiver includes clock generation and recovery circuitry that enables a data serialization factor of five. At a maximum data rate of 1.8 Gb/s, the optical transmitter, receiver, and clocking circuitry consume 12.6, 4.5, and 6.5 mW, respectively, for a total link electrical power dissipation of 23.6 mW. To the best of our knowledge, this is the first demonstration of an interconnect transceiver operating at 1550 nm with a III-V output device directly integrated to the CMOS.     

Flip-Chip Bonding of MEMS Scanner for Laser Display Using Electroplated AuSn Solder Bump

A MEMS scanner has been flip-chip bonded by using electroplated AuSn solder bumps. The microelectromechanical systems (MEMS) scanner is mainly composed of two structures having vertical comb fingers. To optimize the bonding condition, the MEMS scanner was flip-chip bonded with various bonding temperatures. Scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) spectroscopic system was used to observe the microstructures of the joints and analyze the element compositions of them. The die shear strength increased as the bonding temperature increased. During the thermal aging test, the delamination occurred at the interconnection of the MEMS scanner bonded at 340 degC. It is inferred that the Au layer serving as pad metallization has been dissolved in the molten AuSn solder totally, and subsequently the Cr layer was directly exposed to the AuSn solder. Judging by the results of both die shear test and thermal aging test, the optimal bonding temperature was found to be approximately 320 degC. Finally, using this MEMS scanner, we obtained an optical scanning angle of 32deg when driven by the ac control voltage of the resonant frequency in the range of 22.1-24.5 kHz with the 100-V dc bias voltages