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The use of adhesively bonded joints in place of traditional joining techniques such as bolted or rivet joints is becoming greatly popular in recent years. Interfacial stress in the adhesive is critical to the strength of adhesively bonded joints. It is necessary to predict the interfacial stresses accurately to ensure the safety of joints. In this work, an analytical model is explicitly presented to evaluate the stresses in a double lap joint. The equilibrium equations in the adhesive overlap region are derived on the basis of elasticity theory. The governing equations are presented in terms of shear and peel stresses in the adhesive. Analytical solutions are derived for the shear and peel stresses, which are considered to be the main reason for the failure of the double lap joint. To verify the analytical solutions, the finite element method is conducted using the commercial package ANSYS. Results from the analytical solution agree well with finite element results and numerical investigations available in the literature. The effect of the adhesive thickness, shear modulus, adherend Young&rsquo, s modulus and bonding length on the shear and peel stresses in the adhesive of the double lap joint are studied. Numerical results demonstrate that both the maximum shear and peel stress occur at both ends of the bonding region. The maximum values of the shear and peel stresses increase as the adhesive thickness decreases and as the adhesive shear modulus increases provided that the adhesive thickness is sufficiently small. The simplicity and capability to obtain analytical expressions of the shear and peel stresses for double lap adhesive bonded joints makes the proposed analytical model applicable for the stress analysis and preliminary structural design.

The development of ultrafine-pitch microbumps and the thermal compression bonding (TCB) process for advanced 3-D stacking technology are discussed in this paper. Microbumps, consisting of Cu pillars and thin Sn caps with a pitch of 25 μm, are fabricated on an Si chip by the electroplating method. Total thickness of the Cu pillar and the Sn cap is 10 μm. Electroless nickel and immersion gold pads with a total thickness of 4 μm are fabricated on an Si carrier. TCB of the Si chip and the Si carrier is conducted on an FC150 flip-chip bonder, and a good joining with higher than 10-MPa die shear strength is achieved. After bonding, the bond line thickness between the Si chip and the Si carrier is filled with the selected capillary underfill material. Void-free underfilling is achieved with underfill materials which have a fine filler size. Ninety percent of the bonded samples can pass the thermal cycling test (-40/+125°C) with 1000 cycles and the highly accelerated temperature/humidity stress test (130°C , 85% RH) for 96 h.

Fabrication of high aspect ratio through silicon vias (TSVs) in a Si interposer and fine pitch solder microbumps on a top Si die is discussed in this paper. Chip stacking result of the Si interposer and the top Si die is also presented. TSVs with 25 μm in pitch and aspect ratio higher than 10 are etched with BOSCH process. To avoid difficulties in wetting the sidewall of the TSVs, bottom-up plating method is used to fill the TSVs with Cu. In order to fill the TSVs from bottom, the TSVs are first sealed from the bottom by plated Cu with plating current of 1 A. The plated Cu is used as a seed layer and bottom-up plating is then conducted with plating current of 0.1 A. Good filling without voids or with only tiny voids has been achieved. Electroless nickel/immersion gold is plated on top of the TSVs as under bump metallurgy pads. On the top Si die, Cu pillars/Sn caps with 16 μm in diameter and 25 μm in pitch are fabricated with electroplating method. After chip stacking, interconnections are formed between them through the solder microbumps and the TSVs.

The modulus of rupture of Al2O3-spinel castables containing 20 wt% Al2O3-rich MgO-Al2O3 spinel and 1.36-2.04 wt% CaO generally increases with an increase in both CaO content and temperature from 1300° to 1500°C, but it remains virtually constant from 1000° to 1300°C. Microscopic observation of the castable fired at 1500°C for 3 h reveals the growth of some CA6 crystals out of the Al2O3-rich spinel grains in the bonding matrix of the castable. The bond linkage between the CA6 and spinel grains in the matrix is believed to cause both the CaO content and temperature dependence of the hot strength of the Al2O3-spinel castables as well as the hot strength enhancement of high-Al2O3 castables with addition of Al2O3-rich spinel.

A comparison is made of predictions of the structural evolution of Al 2 O 3 SiO 2 SiCC refractories during firing and under slag attack made with the FACT computation package, and experimental observations including the development of a decarburised zone, relative wear of different materials and phases present as determined by microstructural and X-ray examination. The corrosion tests were carried out under oxidising conditions and with slags both containing and free of iron oxide. Two different base refractory compositions were used, one containing clay and one without. The additives considered included 5% Al, 10% Si, 5% B 4 C, 5% BN, 5%B 2 O 3 , and 15% Si 3 N 4 . Experimentally, good wear resistance was associated with the predicted content of SiC in the refractory in the as-fired condition. The most effective additives were silicon and B 4 C, whilst the most deleterious was B 2 O 3 . These results are interpreted in terms of the thermochemical predictions, including the variation in oxygen potential with slag attack and it is shown that the materials can be ranked in the same order as observed in the wear tests.

An InAs-GaAs quantum ring infrared photodetector has been fabricated successfully. The photodetector demonstrates a cutoff wavelength at 175 mum (1.7 THz) and the detectivity of 1.3times107 cm Hz1/2/W at 80 K. The precise control of the In(Ga)As ring height by capping GaAs layer thickness is responsible for extension of the detector response to terahertz range.

The microstructures of Al2O3–SiO2–SiC–C refractory matrices with aluminum, silicon, Si3N4, BN, B2O3, and B4C additives are characterized before and after a crucible slag test, and the phases present are compared to those expected at thermodynamic equilibrium. The carbon content dominates the resistance to CaO–MgO–Al2O3–SiO2 slag penetration, while the viscosity of liquid phases present has a significant influence when the matrix carbon contents are similar. Silicon and Si3N4 additives reduce slag penetration resistance because of indirect oxidation of carbon to form SiC. B4C, in particular, and B2O3 also reduce slag penetration resistance because of formation of a more fluid boron-containing liquid, while aluminum and BN addition have no significant effect. Carbon and BN hardly react with the slag, while SiC partially reacts with it, leading to deposition of carbon as a dense layer. Corundum present in the refractories also readily dissolves in the slag. Microstructurally, slag penetration resistance is associated with the dense carbon layer located at the slag-refractory interface.

The thermal conductivity of three commercial-quality alumina-spinel castables containing 90–96 wt% A12O3 was measured in the range room temperature to 1000°C by a hot wire method. Experimental results indicate that the thermal conductivity increases with an increase in coarse aggregate content; higher corundum content and purer alumina aggregates are more important than coarse aggregate content for higher thermal conductivity of alumina-spinel castables.

Three dimensional (3D) stacking technology has been purposed to meet miniaturization trend, high performance, and multi-function electronic products. Chip stacking with through silicon via (TSV) and high density lead free interconnection are believed to realize 3D stacking package. Due to the narrow dispensing request for multi-chip connection, non-conductive paste (NCP) is one of the solutions to replace capillary underfill. Nevertheless, voidless control and wettability are two critical challenges for large dies size flip chip ball grid array (FCBGA) 3D package. In this paper, fine pitch u-bump for large die size 3D stacking using thermal compression bonding (TCB) with NCP is demonstrated. In order to achieve voidless, bonding parameter was studies in different pre-heat time. The effect of bonding conditions such as force, temperature, and time on wettability has been performed. The results showed that longer pre-heat time could accomplish voidless. The u-bump wettability exhibited relationship between TCB parameters and characteristics of NCP. Finally, reliability test was tested for NCP properties discussion.

Ceramic bodies of mullite composition were prepared from a mixture of calcined alumina and raw kaolin with the addition of bastnasite (rare-earth oxide concentrate) at up to 3% wt and fired at 1400–1650°C. The bastnasite addition effectively enhances mullite formation but the effect diminishes rapidly with increasing temperature. The Al 2 O 3 -rich composition is characteristic of the mullite. The ceramic green compacts with the bastnasite addition can only approx. reach 96% theoretical density at best when heated at 1550–1650°C. The pores in the fired bodies with the bastnasite addition are smaller and uniformly distributed; localized, larger pores are found in the fired bodies without the addition. The slag resistance of the refractories increases slightly with an increasing amount of bastnasite added to the bonding matrix. Bastnasite is not an effective additive for enhancing the slag resistance of steel-plant refractories. The peak temperature in DTA and the valley temperature in the dilatometric analysis, are indicative of mullite formation: the former was found to be 1412°C without bastnasite addition and 1368°C with 3% wt bastnasite addition while the latter was found to be 1420°C without bastnasite addition and 1350°C with 3% wt bastnasite addition.

Slag-resistant tests were performed in fired crucibles made from raw kaolin and calcined alumina powders containing 65, 72, 78 wt% Al2O3 and 65 wt% Al2O3 + 6 wt% Cr2O3. The crucible tests showed that a 2-mm-wide protective layer was visible between slag and non-reaction zones in the 65 wt% Al2O3 crucible and that no such layer appeared in the 72 and 78 wt% Al2O3 crucibles. Reflected light microscopy revealed that in the 65 wt% Al2O3 + 6 wt% Cr2O3 crucible the slag zone was less fluid and the reaction zone less slag penetrative and reactive, as compared with others. The expansion or the shrinkage trend of the bauxite aggregate brick bonded with raw kaolin and calcined alumina powders after more than 3 h reheating at 1500°C depends mainly on the alumina content of the bonding matrix regardless of aggregate mix grading, and previous firing temperatures for green compacts. The continuing positive reheat linear change of bauxite-based, high-alumina, torpedo ladle brick, which promotes mortar joint tightening and retards pencilling slag attack, can be obtained by the combined action of the bonding matrix containing 65 wt% Al2O3 and a lower temperature firing prior to services.

Since 3D-IC becomes popular nowadays, solder micro-bumps plays an important role to develop TSV technology. This study verifies solder micro-bump efficiency via cracking as index. The micro-bump cracking is observed at the interface of intermetallic compound (IMC) layer after Si chip and Si carrier bonding. It was found that P-rich Ni layer will perform weaker and brittle solder joint by means of EDS. Figure 1 shows the cross section schematic drawing as 3D chip stacking for a Si chip and a Si carrier. The solder micro-bumps and under bump metallurgy (UBM) pads are fabricated on the Si chip and the top side of Si carrier respectively. The TSVs in Si carrier functions as interconnects. After flip chip assembled Si chip and Si carrier, the whole assembly is joint onto a bismaleimide triazine (BT) substrate with redistribution layer and solder joints through by bottom of Si carrier. In this study, the Si carrier was patterned with the diameter and depth by 50um and 120um respectively at room temperature with BOSCH process. The smoother scallop was achieved below 150nm. Excellent passivation step coverage for 39% ≃ 50% from via top to bottom side was also obtained. TSV formation processed by electroplating Cu and X-ray result shows void free in TSV. After TSV formation, the electrical nickel and immersion gold (ENIG) was used for the UBM. The total thickness of 50μm Ni/Cu and Sn/Ag solder micro bumps were fabricated by electroplating on top of Si chip.

In order to uniformly expose Cu via, TSV wafer thinning becomes much critical contrary to conventional process. The complete wafer thinning process is expected composed of not only grinding, but also handling. This study develops advance wafer thinning process from temporary carrier bonding to carrier de-bonding that also includes grinding and backside processes. In this case, the bonded wafer thinning target is 100um for backside process. Void-free carrier bonding and bump after backside processes could be addressed. The carrier de-bonding process performs no wafer crack and residue. Moreover, whole wafer thinning process never suffers from Cu scratching. In this study, Under Bump Metallization (UBM) and bump were laid on the backside of Through Silicon Via (TSV) wafer. The wafers composed of various surface structures were carried out to bond glass carrier. The structure difference above came from various designs on UBM and bump. These designs may be backside UBM only, Redistribution Layer (RDL) + UBM, and even bumps on UBM. All the wafers were prepared through passivation patterning, sputtering, solder printing, plating and reflow. Among these processes, the wafer preparation also requires necessary passivation curing, sputtering for Cu seed deposition, and electroplating to form solder bump.

Refractory bodies of 65 wt% Al 2 O 3 were prepared from a mixture of calcined alumina and raw kaolin with the addition of Cr 2 O 3 up to 15 wt%. The Cr 2 O 3 addition effectively enhances slag resistance and reduces mullite formation. Petrographic analysis of the refractories after the slag test suggests that Cr 2 O 3 increases the viscosity of both the glassy phase in the refractory as well as the slag, thereby retarding slag penetration and reaction at elevated temperature.

The submodeling technique is a powerful analysis tool. The method promotes more accurate analysis and also helps enhance productivity. It has been shown that by using displacement-force cut boundary condition method, it can be made even more versatile. The local stress phenomena of the solder microbump have been solved with this approach to demonstrate the concept. From the simulation model, it is known that the ENIG pad thickness has an effect on the aluminium pad stress in the silicon chip. This is important as the shear stress will damage the pad and circuitry on the chip. Previously this is not reported in other literatures as there is no strain gage available that can measure such a small dimension.

High density three dimensional (3D) interconnects formed by high aspect ratio through silicon vias (TSVs) and fine pitch solder microbumps are presented in this paper. The aspect ratio of the TSV is larger than 10 and filled with Cu without voids; there are electrical nickel and immersion gold (ENIG) pads on top of the TSV as under bump metallurgy (UBM) layer. On the Si chip, Cu/Sn solder microbumps with 16µm in diameter and 25µm in pitch are fabricated. After singulating the Si chip and the Si carrier, there are joined together and the interconnection is formed between them through the solder micro bumps and the TSV.

In this paper, frequency selective surface with random distributed resistance patches (RRDFSS) has been proposed and the effects of occupancy factor, distribution and surface resistance have been studied numerically with HFSS. The results show that occupancy factor, distribution and aggregative quantities have notable effects on absorbing properties of the proposed RRDFSS and absorbing performances could be improved greatly in wide band while using suitable surface resistance. RRDFSS can be used in composite absorbing material and be easily realized.

The enhanced optical transmission through the annular aluminum metal with different number of concentric rings arranged in a long-range periodic structure on the silicon substrate is investigated. The measured transmission spectra demonstrate that the surface plasmon modes depend sensitively on the structural parameters of the metallic rings. The degenerate (1,0), (1,1), and (2,1) Al∕Si surface plasmon modes are determined by the long periodicity of the structure. The localized modes in cavities with different length can be observed in this structure as well. These phenomena suggest that both surface plasmons and localized cavity modes are excited within super unit cell.

This paper reports the optical properties of Al∕Si structure and trilayer Ag∕SiO2∕Ag plasmonic thermal emitter with different concentric metal rings on top metal film. It is found that when the metal width is smaller than 40% of the period (=gap+metal width), the (1,0) Al∕Si surface plasmon leads to a maximum in the transmission spectra; otherwise, the opposite is observed. The dispersion relations and emission spectra of the plasmonic thermal emitters were investigated. The emission peaks are independent of the gap width and redshift as annular metal width increases. This phenomenon suggests the excitation of Fabry-Perot type resonance within cavity of Ag∕SiO2∕Ag structure. No (1,0) Ag∕SiO2 surface plasmon was observed.