Fuad M. Khoshnaw

Glass as a Substrate for High Density Electrical Interconnect

The high volume production of substrates able to support high density interconnection is becoming increasingly difficult as the pitch of devices continues to decrease. An important issue is the alignment of microvias and pads which is made particularly challenging by the dimensional instability of traditional organic substrates. In this work, glass has been investigated as an alternative substrate material. Glass offers potential advantages including: electrical insulation, dimensional stability, thermal expansion similar to Si and optical transparency. This paper examines manufacturing processes for the preparation of substrates built up from 50 to 100 ¿m thick glass sheets. Excimer laser machining was used to form microvias and tracks in the glass which were metallised using electroless plating methods. Using a photoresist layer during the laser machining process helped to reduce debris on the glass surface and could be used to direct the subsequent deposition of electroless copper or nickel such that circuit patterns could be created. Lamination of the thin glass sheets was investigated using direct glass to glass bonding and through the use of an intermediate layer. A method for the combination of these techniques to create multilayer substrates is proposed.

Challenges in the manufacture of glass substrates for electrical and optical interconnect

For high density electrical interconnect, the production of fine feature, fine pitch substrates is difficult, due to limitations in manufacturing processes and the dimensional stability of conventional laminate materials. In order to enable the further uptake of flip-chip technology, new materials and methods for substrate manufacture are required. Glass as a substrate material offers a number of potential advantages including dimensional stability and close coefficient of thermal expansion match to Si. Furthermore, its optical clarity makes it suitable as a conduit for the transmission of light signals for applications in the growing area of optical interconnect. This paper describes preliminary work to investigate the key challenges of laser machining, metallization and lamination that are involved in the manufacture of multilayer substrates from thin glass sheets. Laser machining has been used to create microvias and other features in the glass and work is underway to determine appropriate process windows. The metallization of glass using electroless copper has been investigated and found to be very dependent on the surface pre-treatments. Finally, pressure assisted-low temperature bonding has been considered as a method for the lamination of the glass sheets to create a multilayer structure

Challenges in the Manufacture of Glass Substrates for Electrical and Optical Interconnect

For high density electrical interconnect, the production of fine feature, fine pitch substrates is difficult, due to limitations in manufacturing processes and the dimensional stability of conventional laminate materials. In order to enable the further uptake of flip-chip technology, new materials and methods for substrate manufacture are required. Glass as a substrate material offers a number of potential advantages including dimensional stability and close coefficient of thermal expansion match to Si. Furthermore, its optical clarity makes it suitable as a conduit for the transmission of light signals for applications in the growing area of optical interconnect. This paper describes preliminary work to investigate the key challenges of laser machining, metallization and lamination that are involved in the manufacture of multilayer substrates from thin glass sheets. Laser machining has been used to create microvias and other features in the glass and work is underway to determine appropriate process windows. The metallization of glass using electroless copper has been investigated and found to be very dependent on the surface pre-treatments. Finally, pressure assisted ? low temperature bonding has been considered as a method for the lamination of the glass sheets to create a multilayer structure.

The pressure angle effects of spur gears on stress concentration factor

Purpose – The purpose of this paper is to investigate the effect of pressure angle, and module of spur gear teeth on stress concentration factor, using photoelasticity method, and numerical MSC/NASTRAN finite element package.Design/methodology/approach – The stress concentration factor is determined as a ratio between maximum stress (determined in the fillet radius by photoelastic and finite element methods), and nominal stress (calculated by a common standard formulas). In order to specify the geometric parameters (height and thickness) of gears, both standard Deutsches Institut fur Normung (DIN)/Japanese Gear Manufactures Association (JGMA), and five other non‐standard approaches are used.Findings – The results show that the stress concentration factor increases by decreasing the pressure angle. In addition, the values which are obtained by finite element analyses exhibit more uniformity than photoelastic method.Practical implications – An accurate determination of stress concentration factors will limi...

Corrosion behaviour of nitrided low alloy steel in chloride solution

Purpose – The corrosion behaviour of low alloy steel type AISI 4130 (before and after nitriding) and austenitic stainless steel type AISI 304L were studied in tap water +3.5 per cent NaCl. A liquid nitriding process had been applied on the low alloy steel.Design/methodology/approach – The tests that were carried out in this study were anodic polarization, rotating bending fatigue and axial fatigue using compact tension (CT). For determining the corrosion potential and pitting potential (breakdown potential) for the alloys, anodic polarization curves were established using the potentiodynamic technique. Rotating bending fatigue tests were used to calculate the fatigue strength and damage ratio. Using linear elastic fracture mechanics, the CT specimens were prepared for determining the threshold stress intensity factor, fatigue crack growth rate and fracture toughness in air and in the solution.Findings – The results showed that nitrided specimens showed higher fatigue strength in air compared to stainless ...

Glass Multilayer Lamination for PCB Manufacture using Pressure Assisted Low Temperature Bonding

Thin glass sheets may be a suitable alternative to FR-4 for the preparation of substrates for high density interconnect. However to build such substrates, the bonding of glass layers is necessary to create multilayer structures. In this work, a pressure-assisted low-temperature bonding technique for glass lamination was investigated. Glass, of thickness 100mum, was used as a substrate material and was selected as it has a coefficient of thermal expansion close to that of silicon. Cleaning and pre-treatment of the glass was critical to achieve good bonding at the interface. Three different cleaning solutions were tested: concentrated nitric acid, potassium hydroxide solution and Decon 90 solution, for which contact angle measurements were used to determine the hydrophilicity of the resultant surfaces. Obtaining perfectly clean surfaces was problematic due to the high surface energy of the cleaned glass. Experiments showed that the best way to avoid contaminants was achieved by assembling each pair of cleaned glass sheets together whilst in filtered deionised water. Treatment in a vacuum oven enabled a preliminary bond to be achieved. Final bonding was carried out by applying pressure to the samples in a clamping device, which was placed in a convection oven between 200 and 300degC for up to 48 hrs. Thermal cycling tests were used to evaluate the bonding. Permanently bonded samples were studied using a fatigue test to evaluate the resistance of the bonded sheets to delamination and/or fracture.

Effect of aging time and temperature on intergranular corrosion of aluminium alloys

Purpose – Two types of aluminium alloys, 2024‐T3 and 7075‐T6, having been selected, this study aims to investigate the effect of metallurgical aspects on intergranular corrosion.Design/methodology/approach – To determine and evaluate the metallurgical effects of heat treatments on corrosion behaviour of these alloys, G67 ASTM test was selected.Findings – The results showed that with increasing the aging time in aluminium alloy type 2024‐T3 the susceptibility to intergranular corrosion increases, while in type 7075‐T6 with increasing aging time the intergranular corrosion rate remains nearly unchanged.Practical implications – As these results refer to precipitate the intermetallic compound phases, the amount of these phases increases with the increase of the aging time in both alloys.Originality/value – The investigations showed that the phases that initiate in 2024‐T3 act as anode sites, while in 7075‐T6 they act as cathode sites.

Evaluation the moisture effects on the performance of electronic devices

The moisture uptake has different effects on the performance of electronic components; besides electrochemical migration, moisture affects increasing the dielectric constant of electronic substrates, i.e. multichip module, printed circuit boards and hermetic packages, consequently this cause electrical failures and signal delay. This study explains the effects of moisture and air contaminates on the performance of electronic equipments.

Stress Corrosion Cracking Behaviour of Welded Duplex Stainless Steel

This study investigated stress corrosion cracking of two welded stainless steel alloys, austenitic 304L and duplex 2205, in an acidic chloride solution. Different heat inputs are selected for welding the alloys, using tungsten inert gas, with and without filler metal. The slow strain rate technique is utilized to estimate the susceptibility of each weldment to stress corrosion cracking. Different strain rates are used, and the experiments showed that the strain rate equal to 1.66x10-6/sec is a critical value that can be used for assessing the susceptibility of the alloys to corrosion cracking. A numerical index used in this study to evaluate this susceptibility, which is based on a ratio between elongation percent of each alloy in the solution to that in the air. The results showed that the austenitic alloy has higher ductility than duplex in air, while there was not a big difference between both alloys in the solution. Increasing the heat input in autogenous welding caused a brittleness, i.e. less elongation, for both alloys. The results showed that the austenitic alloy is exposed to stress corrosion cracking in the solution, before and after welding, with or without filler metals. On the other hand, the duplex alloy showed higher resistance to stress corrosion cracking than the austenitic alloy due to the high chromium content, and it is dual phase.

Electrochemical migration of electronic components at sea environments - characterizations and solutions

Seawater is associated with two main effects, high humidity and chloride ions, that have direct influence on electrochemical migration (ECM) occurrence in electronic components which might eventually lead to short circuit failure. This phenomenon occurs when metal ions migrate from anode electrode to cathode, via electrolyte, under bias voltages. Other factors contribute to cause this phenomenon such as pH, temperature, chemical composition of the substrate, etc. In order to reduce the possibility of ECM on electronic devices, in this study information and data from other literatures have been collected, to analyse and investigate the interactions between the factors that affect this phenomenon. The main concept in this study is characterisation the interactions and interferences between the chemical composition of substrate, e.g. printed circuit board (PCB), i.e. resin: glass ratio, with ability for absorption, which changes their dielectric properties, and capacitance, and showing how they affect ECM of electronic devices at seawater. Meanwhile, theoretical solutions would be suggested to reduce the effect of this phenomenon at humid environments.