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Article
Publication date: 1 June 2005

Abstract

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Soldering & Surface Mount Technology, vol. 17 no. 2
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 April 2000

Anne Seppälä, Kimmo Saarinen and Eero Ristolainen

Small and low cost unencapsulated SMD plastic film capacitors were manufactured with different terminal metal compositions and dielectric materials. Capacitors made with a…

Abstract

Small and low cost unencapsulated SMD plastic film capacitors were manufactured with different terminal metal compositions and dielectric materials. Capacitors made with a polyethylene naphthalate film dielectric were produced using a winding method. The terminals were metallized using the flame spraying process. The terminals of the test capacitors consisted of three different metal layers. The base metal layer, which was aluminum, was coated with brass or copper. The top layer was a sprayed lead‐free, tin‐based solder to ensure the solderability of the terminals. The reliability of the unencapsulated test capacitors was evaluated using standard temperature cycling, humidity storage, and high temperature environmental tests. Solderability and resistance to soldering heat were tested by mounting the test capacitors using the reflow soldering technique. The electrical properties including capacitance, insulation resistance, and dissipation factors at 1kHz and 100kHz were verified.

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Soldering & Surface Mount Technology, vol. 12 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 April 2004

Minna Arra, Todd Castello, Dongkai Shangguan and Eero Ristolainen

The mechanical properties of Sn/Ag/Cu solder joints in combination with different component lead coating materials (Ni/Pd/Au, Sn/15 per cent Pb, Sn/2 per cent Bi, and Sn…

Abstract

The mechanical properties of Sn/Ag/Cu solder joints in combination with different component lead coating materials (Ni/Pd/Au, Sn/15 per cent Pb, Sn/2 per cent Bi, and Sn) are studied in this work using a lead pull test and free fall drop test. The results of this study show that the Sn/2 per cent Bi coated components provide the best performance under the drop impact loading followed by the Sn/15 per cent Pb, Sn and Ni/Pd/Au coated components. Failure modes and the structure of the coating surfaces were examined from cross‐sectioned samples using a scanning electron microscope. Furthermore, the wetting of the leads by the solder and thickness of the IMC layers were studied.

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Soldering & Surface Mount Technology, vol. 16 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 March 2005

Sami T. Nurmi, Janne J. Sundelin, Eero O. Ristolainen and Toivo K. Lepistö

To study the behaviour of voids in PBGA solder joints and their influence on the lifetime of lead‐free solder joints.

Abstract

Purpose

To study the behaviour of voids in PBGA solder joints and their influence on the lifetime of lead‐free solder joints.

Design/methodology/approach

The behaviour of voids was studied using micro via and land pad PWBs, PBGA components, and by measuring voids in the solder joints. The lifetimes of solder joints were tested using accelerated temperature tests.

Findings

Number of factors affecting the solder joint lifetimes were found. The voids were discovered to have a significantly large influence on the solder joints.

Practical implications

The findings can be used to achieve better soldering results, methods, and designs.

Originality/value

In this paper, the effect and the behaviour of voids were studied profoundly. The findings can be valuable to researchers and process personnel.

Details

Soldering & Surface Mount Technology, vol. 17 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 1 April 2003

Anne Seppälä, Kati Aalto and Eero Ristolainen

Flip chip assembly using anisotropic conductive adhesives offers an interesting alternative for making high‐density interconnections. The use of conventional organic…

Abstract

Flip chip assembly using anisotropic conductive adhesives offers an interesting alternative for making high‐density interconnections. The use of conventional organic printed circuit boards makes this technique even more attractive. However, a low‐cost adhesive flip chip bonding process will require a reduced bonding cycle time or the use of multi‐head joining equipment. Adhesive flip chip bonding is characterized by a long bonding cycle time due to the relatively long curing time of adhesives and the need for simultaneous application of pressure during the curing process. In soldered flip chip techniques, the bonding time per assembly is shorter, because all the chips on the substrate can be soldered in a reflow oven at the same time. In this study, the minimum pre‐curing time needed to make a reliable adhesive joint was determined using one commercial anisotropic conductive adhesive film used on FR‐4 substrates. The results are promising, since bonding time reduction from 40 s to 10 s does not reduce the joint reliability.

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Soldering & Surface Mount Technology, vol. 15 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 April 1999

Aulis Tuominen, Eero Ristolainen and Ville Lehtinen

Owing to the incessant demand for reductions in the size of portable electronics, new dense packaging technologies are required. Reflow soldering is still mainly used for…

Abstract

Owing to the incessant demand for reductions in the size of portable electronics, new dense packaging technologies are required. Reflow soldering is still mainly used for component joining on the substrate. In tiny joints such as those in flip chip (FC) assemblies the flux effect is vitally important and needs to pass a narrower performance window than in ordinary surface mount technology (SMT). The determination of the suitability of a flux, as reported in this paper, is twofold; first, the flux must perform well in its intended purpose and second, the flux must not leave harmful residues causing leakage or electromigration. The first test used was the wetting balance test for all fluxes. Fluxes accepted on the basis of the wetting tests were then subjected to the surface insulation resistance test (SIR).

Details

Soldering & Surface Mount Technology, vol. 11 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 August 2002

Sami Tapani Nurmi and Eero Olavi Ristolainen

This paper will describe tests of the interconnect reliability of BGA components with tin‐lead bumps soldered with lead‐free solder paste during temperature cycling…

Abstract

This paper will describe tests of the interconnect reliability of BGA components with tin‐lead bumps soldered with lead‐free solder paste during temperature cycling. Tin‐lead BGA components soldered with tin‐lead solder paste and lead‐free BGA components soldered with lead‐free solder paste were used as a reference. The lead‐free solder used was eutectic tin‐silver‐copper. Two kinds of surface finishes were used on the printed circuit boards (PCB), an immersion gold over electroless nickel and an organic solderability preservative. The test PCBs were temperature‐cycled for 2500 cycles in the range of −40°C to +125°C and they were continuously electrically monitored during the cycling. The results of the temperature cycling test showed that lead‐ containing BGA components soldered with lead‐free solder paste don't show any serious reliability risks and can actually withstand temperature cycling stresses better than entirely lead‐free BGA assemblies.

Details

Soldering & Surface Mount Technology, vol. 14 no. 2
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 December 2005

Janne J. Sundelin, Sami T. Nurmi, Toivo K. Lepistö and Eero O. Ristolainen

To provide further knowledge of the effect of solder composition and PCB surface finish on the creep properties of lead‐free SnAgCu solder joints.

Abstract

Purpose

To provide further knowledge of the effect of solder composition and PCB surface finish on the creep properties of lead‐free SnAgCu solder joints.

Design/methodology/approach

Single‐overlap shear specimens were prepared for the creep testing. The test matrix included three different SnAgCu pastes with hypoeutectic, eutectic, and hypereutectic compositions. An Sn63Pb37 solder paste was used as a reference. The PCB finishes used were NiAu, organic solderability preservative (OSP) and immersion tin. The creep tests were performed at 85 and 105°C using a dead‐weight system.

Findings

According to the results, the SnAgCu solder with eutectic or near‐eutectic composition is the safest choice when the creep behaviour of solder joints is considered. Of the three different PCB surface finishes, immersion tin is the most favourable choice for use with SnAgCu joints when creep is the predominant deformation mechanism in the joints. On the NiAu finish the creep properties of SnAgCu solder joints were significantly weaker in eutectic and hypereutectic SnAgCu joints than on Sn and OSP.

Originality/value

The results can be used to enhance the reliability of SnAgCu joints in demanding conditions, when special attention is paid to the choice of PCB surface finish and SnAgCu solder composition.

Details

Soldering & Surface Mount Technology, vol. 17 no. 4
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 August 2002

Minna Arra, Dongkai Shangguan, Eero Ristolainen and Toivo Lepistö

The wetting performance and intermetallic formation of a Sn/Ag/Cu alloy on printed circuit board (PCB) surfaces and on component terminations were studied in this work…

Abstract

The wetting performance and intermetallic formation of a Sn/Ag/Cu alloy on printed circuit board (PCB) surfaces and on component terminations were studied in this work. Two different PCB surface finishes, immersion gold over electroless nickel (Ni/Au) and an organic solderability preservative (OSP), were studied. Chip components with Sn/Pb coating and a gull‐wing type component with 100% Sn coating were used in these experiments. Different reflow profiles were tested, and the dependence of the wetting performance, intermetallic layer thickness and the microstructure of the solder joints on the reflow profile were investigated.It was found that reflow process conditions did not significantly influence the spreading or intermetallic formation on either of the surfaces. Neither the wetting onto the component nor the general microstructure of the solder joints varied significantly with the reflow profile. When a Sn/Pb ‐coated component was used, the content and size of Pb‐rich phases in the solder joint increased with a longer time above liquidus or a higher reflow peak temperature.

Details

Soldering & Surface Mount Technology, vol. 14 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

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