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1 – 10 of 32
Article
Publication date: 6 June 2016

Guang Chen, Li Liu, Vadim V. Silberschmidt, Y.C. Chan, Changqing Liu and Fengshun Wu

This paper aims to systematically study the effect of reinforcement type, processing methods and reflow cycle on actual retained ratio of foreign reinforcement added in solder…

Abstract

Purpose

This paper aims to systematically study the effect of reinforcement type, processing methods and reflow cycle on actual retained ratio of foreign reinforcement added in solder joints.

Design/methodology/approach

Two kinds of composite solders based on SAC305 (wt.%) alloys with reinforcements of 1 wt.% Ni and 1 wt.% TiC nano-particles were produced using powder metallurgy and mechanical blending method. The morphology of prepared composite solder powder and solder pastes was examined; retained ratios of reinforcement (RRoR) added in solder joints after different reflow cycles were analysed quantitatively using an Inductively Coupled Plasma optical system (ICP-OES Varian-720). The existence forms of reinforcement added in solder alloys during different processing stages were studied using scanning electron microscope, X-ray diffractometry and energy dispersive spectrometry.

Findings

The obtained experimental results indicated that the RRoR in composite solder joints decreased with the increase in the number of reflow cycles, but a loss ratio diminished gradually. It was also found that the RRoR which could react with the solder alloy were higher than that of the one that are unable to react with the solder. In addition, compared with mechanical blending, the RRoRs in the composite solders prepared using power metallurgy were relatively pronounced.

Originality/value

Present study offer a preliminary understanding on actual content and existence form of reinforcement added in a reflowed solder joint, which would also provide practical implications for choosing reinforcement and adjusting processing parameters in the manufacture of composite solders.

Details

Soldering & Surface Mount Technology, vol. 28 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 September 2005

Dezhi Li, Changqing Liu and Paul P. Conway

To study the influence of storage time and environment on the solderability of electroless nickel plated samples with Sn‐3.8Ag‐0.7Cu and Sn‐3.5Ag lead‐free solders and to provide…

Abstract

Purpose

To study the influence of storage time and environment on the solderability of electroless nickel plated samples with Sn‐3.8Ag‐0.7Cu and Sn‐3.5Ag lead‐free solders and to provide criteria for the use of an electroless nickel (Ni‐P) under bump metallization (UBM) without immersion gold protection.

Design/methodology/approach

Electroless nickel coatings were deposited onto pure aluminium foil through a procedure developed for the UBM of wafers prior to flip chip bumping. Their solderability with lead‐free solders was studied using the wetting balance technique. Samples stored in different environments for different periods of time were tested to study the dependence of the solderability of Ni‐P coatings on the storage time and temperature. The degree of oxidation of the Ni‐P coatings was examined by means of X‐ray photoelectron spectroscopy and the surface microstructure and roughness of the coatings were analyzed by scanning electron microscopy and atomic force microscopy.

Findings

It was found that the Ni‐P coatings were unacceptable for direct soldering without the assistance of a flux, due to poor wettability, even when using a freshly prepared Ni‐P coating. Therefore, a suitable flux with nitrogen inerting had to be applied to assist the soldering process. The results also show that the solderability of Ni‐P coatings was affected by the phosphorus content, and the Ni‐P coating with high phosphorus content had a good solderability. The storage time and temperature did not influence the wettability significantly with the assistance of strong flux.

Research limitations/implications

The stability of the plating solution and the consistence of the phosphorus content in the coating are not easily controlled. This has resulted in implications for surface analysis and wetting testing. Ni‐P coatings with different levels of phosphorus content are being investigated in detail.

Originality/value

The value of the paper lies in its study on the solderability of lead‐free solders to Ni‐P coating after storage in different environments and for different periods, which can provide some criteria for the use of Ni‐P UBM without immersion gold protection.

Details

Circuit World, vol. 31 no. 3
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 16 November 2012

Mark W. Sugden, David A. Hutt, David C. Whalley and Changqing Liu

The purpose of this paper is to present an outline of the development of a new process for the formation of flip‐chip interconnections using metal coated polymer microparticles.

Abstract

Purpose

The purpose of this paper is to present an outline of the development of a new process for the formation of flip‐chip interconnections using metal coated polymer microparticles.

Design/methodology/approach

Metal coated polymer microparticles were selectively deposited onto the bondpads of integrated circuits using electrophoresis. Thermocompression bonding was then used to bond the devices to substrates.

Findings

Particles obtained a positive surface charge following immersion in an acidic solution and this surface charge allowed the particles to be deposited electrophoretically directly onto the bondpads of an integrated circuit without the need for patterning. Thermocompression bonding of nickel/gold coated particles to gold coated substrates was achieved at temperatures as low as 160°C.

Research limitations/implications

Further work is needed to test this approach using integrated circuits with finer pitch, and to use patterned substrates for assembly and reliability measurements.

Originality/value

This paper presents a new method for the deposition of metal coated polymer microparticles without the need for any masking or patterning processes for the formation of interconnections on integrated circuits.

Details

Circuit World, vol. 38 no. 4
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 26 January 2010

Hui Xu, Changqing Liu, Vadim V. Silberschmidt, Zhong Chen and Jun Wei

Optimization of the process parameters remains a challenging task in thermosonic wire bonding due to relatively poor understanding of the bonding mechanism. The purpose of this…

Abstract

Purpose

Optimization of the process parameters remains a challenging task in thermosonic wire bonding due to relatively poor understanding of the bonding mechanism. The purpose of this paper is to understand initial bond formation in thermosonic gold wire bonding on aluminium metallization pads and the effect of bonding time on the initiation of bonding.

Design/methodology/approach

A gold wire (20 μm diameter/99.99 per cent wt%) was bonded to aluminium metallization pads (1 μm thick) on a silicon chip using a commercial ball/wedge automatic bonder. Bonding parameters were selected specifically to produce underdeveloped ball bonds so that ball lift‐off occurred during looping process. The lift‐off footprints on the aluminium metallization pads and their evolution were carried out using optical microscopy and scanning electron microscopy. A model is proposed to elaborate the effect of bonding time on initiation of bonding.

Findings

The obtained results showed that metallurgical bonding initiated at the peripheral areas of the contact area situated along the direction of ultrasonic vibration. Those areas extended inwards with bonding time, eventually covering the entire contact area.

Originality/value

This paper describes how bond initiation and its evolution in thermosonic gold wire bonding on aluminium metallization is ascertained by observing lift‐off footprints. The understanding of bonding mechanism benefits the optimization of process parameters and improvement of bondability in thermosonic wire bonding.

Details

Microelectronics International, vol. 27 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 1 March 2003

Changqing Liu and David A. Hutt

The solder interconnection of components to printed circuit boards normally utilises a flux to enable the efficient removal of oxide layers from the metals to be joined. While…

Abstract

The solder interconnection of components to printed circuit boards normally utilises a flux to enable the efficient removal of oxide layers from the metals to be joined. While this produces a strong metallurgical bond, the flux residue left behind after the soldering process can be detrimental to the long‐term performance of the product. Therefore, after assembly, a cleaning process is often employed to remove the residue, however, this incurs extra financial and environmental costs. In this work, organic coatings have been used to preserve copper surfaces in an oxide free state, enabling fluxless soldering to take place. These coatings, if stored appropriately, were found to be effective in preventing the oxidation of copper for several weeks, however, they are readily displaced by the soldering process allowing the active copper surface to be wetted. Wetting balance testing and surface analysis have been used to assess the preservation of copper coupons following storage in air.

Details

Circuit World, vol. 29 no. 1
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 9 February 2010

Guangbin Dou, David C. Whalley, Changqing Liu and Y.C. Chan

Non‐planarity of assemblies and co‐planarity variation effects on anisotropic conductive adhesive (ACA) assemblies have been a concern for ACA users since the materials are first…

Abstract

Purpose

Non‐planarity of assemblies and co‐planarity variation effects on anisotropic conductive adhesive (ACA) assemblies have been a concern for ACA users since the materials are first devised. The primary objective of this paper is to introduce a new experimental method for studying co‐planarity variation effects on ACA assemblies.

Design/methodology/approach

The approach simulates non‐planarity through deliberate chip rotation during the ACA bonding process, thereby locking different levels of co‐planarity variation into ACA test assemblies. Scanning electron microscope (SEM) analysis and electrical joint resistance measurement using the four wire resistance (FWR) method are used to mechanically and electrically examine the connection quality of the ACA assemblies bonded with non‐planar joints, for which the chip and substrate patterns are specially designed to allow joint resistance measurement using the FWR method.

Findings

Typical experiments and their results are presented and analysed. The bond thickness differences between the SEM measurements and calculations indicate that the real rotations are smaller than those predicted by the calculations. The typical experimental results show that the joint resistance reduces as the deformation increases until reaching a relatively stable value after a certain deformation degree.

Research limitations/implications

The average joint resistances in the rotated samples are all bigger than those measured in the un‐rotated samples. This raises the question as to whether the joint resistances of ACA assemblies are more significantly affected by other affects of non‐planarity than just by its effect on bond thickness. However, before this can be confirmed, more research must be done to check if this behaviour happens for different bonding forces.

Originality/value

This paper reports a novel and simple experiment that can be used to examine the effects of co‐planarity variation on the electrical performance of ACA assemblies, by creating different bond thicknesses that are normally difficult to achieve by changing the bonding pressure, since ACA bond thicknesses are not linearly related to the bonding force. The merit of the technique is that there is no need to manufacture chip bumps and substrate pads with different geometries, or to control the bond pressure, to achieve bond thickness variation in ACA assemblies.

Details

Soldering & Surface Mount Technology, vol. 22 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Content available
Article
Publication date: 9 February 2010

Martin Goosey

309

Abstract

Details

Soldering & Surface Mount Technology, vol. 22 no. 1
Type: Research Article
ISSN: 0954-0911

Content available
Article
Publication date: 1 August 2004

76

Abstract

Details

Soldering & Surface Mount Technology, vol. 16 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

Content available
Article
Publication date: 27 November 2007

J.H. Ling

251

Abstract

Details

Circuit World, vol. 33 no. 4
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 15 July 2022

Wei Liu, Zhiping Zhou, Zhaolin Li, Mingxing Li, Qiongwei Li, Zhengrong Ye, Jinxing Yao and Xiankang Zhong

This paper aims to investigate the high-temperature mechanical properties of HS110S steel and its corrosion behaviors in harsh downhole environment.

Abstract

Purpose

This paper aims to investigate the high-temperature mechanical properties of HS110S steel and its corrosion behaviors in harsh downhole environment.

Design/methodology/approach

In this work, mechanical property measurements were carried out from 25°C to 350°C and the scanning electron microscopy was used to observe the fracture morphology. The weight-loss measurements and surface characterization were used to evaluate the corrosion resistance of HS110S steel in harsh downhole environment.

Findings

Results show that the yield strength and tensile strength of HS110S steel at 350 °C are 779 and 861 MPa, respectively. Compared with room temperature, the reduction rate values are both less than 20%. At the high-temperature corrosion environment (350 °C), the static and dynamic corrosion rates are 0.9668 and 1.9236 mm/a, respectively. The generated corrosion products are mainly composed of FeSx, FeCO3 and Fe3O4. Therefore, the HS110S steel applied under such conditions needs to take suitable protective measures.

Originality/value

In general, the HS110 steel has widely used in conventional development conditions (e.g. low H2S or high CO2 environments). However, to the best of the authors’ knowledge, no studies have reported on its application at more than 250°C. Therefore, this work can be a reference to the application of HS110S steel in high-temperature corrosion conditions.

Details

Anti-Corrosion Methods and Materials, vol. 69 no. 5
Type: Research Article
ISSN: 0003-5599

Keywords

1 – 10 of 32