Papers by Keyword: Bonding Process

Abstract: A novel solder bonding material for high-temperature applications based on Cu@Sn core-shell structured particles was developed, and the fabricated Cu@Sn particles were compressed into preforms for die attachment. The reflow temperature for this bonding material could reached as low as 260°C due to the low melting temperature of the outer Sn layer. However, after reflow soldering, the resulting interconnections can withstand a high temperature of at least 415°C, outer Sn layer completely transformed into Cu-Sn intermetallic compounds (IMCs) with high remelting temperatures. The formed bondlines exhibit good electrical conductivity due to the low porosity and the embedded Cu particles in the interconnections. Furthermore, the interconnections also exhibit excellent reliability under thermal shock cycling from-55°C to 200°C. This die attach material is suitable for power devices operating under high temperatures or other harsh environments.

Abstract: As an ideal layout scheme for launch vehicle, bearing co-bulkhead tank can improve the slenderness ratio of launch vehicle, reduce structure weight and increase structure efficiency. In this paper, a novel cryogenic tank co-bulkhead was fabricated by vacuum assisted resin transfer molding (VARTM) process. Consisting of LD10 alloy and polymethacrylimide (PMI) foam-sandwich, the new cryogenic tank co-bulkhead was designed with variable-thickness, hemi-ellipsoid structure, thermal insulation and bearing function. Fundamental temperature distribution, thermal stress and low-temperature load sensitivity of the foam-sandwich co-bulkhead were also assessed by finite element analysis and environment tests in simulated service environment. The results showed that the analog values highly agreed with the test results, and thermal insulation and bearing function of the foam-sandwich co-bulkhead could satisfy the design requirement, which proved the reliability of bonding quality and feasibility of the bonding technique.

Abstract: With the extensive application of composite materials in aircraft structure, effect of the installing process of strain gauge on the strain measuring results of composite structure need to be researched experimentally. In this paper, the composite (T700/LT-03A) was selected to made specimens, and the different grinding manners, surface cleaning agents and bonding agents were adopted respectively as one of strain gauge installing processes. In order to identify influence of the different installing processes on the measuring data accuracy, measured strain data repeatability, linearity and characteristics of measured value oscillation are served as test standard. The compared test results show that the strain installing processes adopted in strength test on traditional metal also apply to the composite (T700/LT-03A) structures strength test.

Abstract: The copper wire has some advantages in thermal performance, mechanical performance, and low cost, which make it can provide the lowest cost flip-chip(FC) package for low I/O density device. The 2D Cu stud bump finite element model was set up by using ANSYS/LS-DYNA with LOLID162 element to dynamic simulate the Cu stud bump bonding shaping process. The stress distribution in the Cu stud bump and the pad during the bonding process were studied, and the influence of pad thickness on the stress distribution of Si chip was also analyzed. The results shows that under the bonding process the Cu bump height is mainly influenced by the bonding pressure and the top shape of the Cu bump is influenced by ultrasonic energy, the increase of pad thickness results in reducing stress concentration inside the Si chip.

Abstract: With the development of MEMS technology, the pressure sensors, one of mature MEMS devices, are expected to better performance. In order to improve sensors performance, supporting vitreous body shape is elongated and thinned. But the variety of the vitreous body shape brings the new difficulties for anodic bonding between the vitreous body and the silicon during the sensors production, and causes that the common bonding process conditions are unavailable and bonding failure rate dramatically increases. Therefore, this article analyzes the bonding process between slender vitreous body and silicon, and researches on the influence of the vitreous body variety on the pressure, temperature and voltage. The results showed that the bonding is the best when the cantilever elastic deformation is less than 0.5mm, interface temperature loaded from the silicon is 415°C and the voltage 1200V is loaded from the position near H=2mm.

Abstract: The gap control problem in hole-machining of Pyrex® wafer by electrochemical discharge machining (ECDM) to obtain a smooth quality and acceptable material removal rate is studied. Analysis of the pulse signals shows that the average current pulse interval is constant, and it is mainly related to the ion translation conditions, such as the electrolyte concentration and the flushing strategy. The most steady and intense average current density can be obtained if the voltage on-time is around 3 times the average current pulse interval and the voltage off-time is 1/4 of the on-time for bubble film dissipation. The utmost allowable feed rate at each depth is recorded as the reference of the feed rate in real continuous machining to avoid the damage to the wafer. By applying 80% of the extreme allowable feed rate, 99.9% quality-proved holes can be acquired. The diametric error at the entrance or exit is within 6%. Besides, there is no crater-like problem around the hole that facilitates the succeeding bonding process. This study contributes to the successful production of reusable optical biological chips with integrated micro fluidic channels.