Environmental issues have an ever‐increasing influence on the selection of material and processes in electronic manufacturing. This paper discusses the use of conductive adhesives…
Abstract
Environmental issues have an ever‐increasing influence on the selection of material and processes in electronic manufacturing. This paper discusses the use of conductive adhesives as a replacement for solder on SMT printed circuit boards. As a result of a world‐wide market survey, a number of conductive adhesives have been selected. One of the two key issues of this paper has been to uncover the market for adhesive types and their composition. The other key issue has been the technical investigation of the influence of component termination and printed circuit surface types on adhesive bonding stability. Four different types of adhesives on two different metal surfaces are compared with conventional solder technology. Each adhesive has been applied to the PCBs by either screen printing or dispensing according to the manufacturer's recommendation, followed by curing. All PCBs went through thermal and humidity cycling followed by electrical measurements of resistance. Finally, all variants have been adhesion tested. All adhesive variants have been microsectioned for metallurgical and microstructure examination. Energy dispersive analysis of X‐ray (EDAX) of the metal particles in the adhesive has been carried out and documented. Rework of conductive joints is briefly commented on. Finally, aspects of occupational health are discussed concerning work with adhesive types. Work with epoxy based adhesives has been brouaht into special focus.
Conductive adhesives (CAs) have been with us for a number of years and have found use in a variety of applications. More recently pressure from environmentalists has led to a…
Abstract
Conductive adhesives (CAs) have been with us for a number of years and have found use in a variety of applications. More recently pressure from environmentalists has led to a reappraisal of the potential of the materials to replace solders in mainstream assembly operations. In this respect they have the advantages that they do not contain lead and do not use fluxes. At present, however, there is no substitute for flow soldering operations which still account for a substantial part of the assembly market. There also appear to be serious grounds for concern regarding the reliability of adhesive joints. In particular, recent reports suggest that their resistance to mechanical shock may be unsatisfactory. In the light of these drawbacks it seems likely that CAs will continue to find niche applications, where their particular properties give them advantages, but that soldering will continue to be the dominant technology for PCB assembly for the foreseeable future.
G.J. Jackson, M.W. Hendriksen, R.W. Kay, M. Desmulliez, R.K. Durairaj and N.N. Ekere
The study investigates the sub process behaviour in stencil printing of type‐6 and type‐7 particle size distribution (PSD) Pb‐free solder pastes to assess their printing limits.
Abstract
Purpose
The study investigates the sub process behaviour in stencil printing of type‐6 and type‐7 particle size distribution (PSD) Pb‐free solder pastes to assess their printing limits.
Design/methodology/approach
Two solder pastes were used in a design of experiments approach to find optimal printing parameters
Findings
Solder paste printing has been achieved to ultimately produce 30 μm deposits at 60 μm pitch for full area array patterns using a type‐7 Pb‐free solder paste. For a type‐6 PSD solder paste, full area array printing was limited to 50 μm deposits at 110 μm pitch. However, for peripheral printing patterns, 50 μm deposits at 90 μm pitch were obtained. The disparities in the behaviour of the two paste types at different geometries can be attributed to differences in the sub‐processes of the stencil printing. The paste release of the type‐6 paste from the stencil apertures at fine pitch was superior to the type‐7 paste, which may be attributed to the finer particle paste producing an increased drag force along the stencil aperture walls. However, the type‐7 paste was able to fill the smallest aperture openings, ultimately to 30 μm, thus producing full array printing patterns at uniquely small pitches.
Practical implications
This advancement in the stencil printing process has been made possible by refinements to both solder paste design and stencil manufacturing technology. Adjustments in the solder paste rheology have enabled successful printing at ultra fine pitch geometries. This, together with selecting appropriate printing parameters such as printing speed, pressure, print gap and separation speed, allows a practical printing process window. Moreover, advancements in stencil fabrication methods have produced “state‐of‐the‐art” stencils exhibiting very precisely defined aperture shapes, with smooth walls at very fine pitch, thus allowing for improved solder paste release at very small dimensions.
Originality/value
The results can be used to present a low cost solution for Pb‐free flip chip wafer bumping. Furthermore, the results indicate that type‐6 and type‐7 solder pastes should be applied to/selected for specific application geometries.
Details
Keywords
J. Lantairès, B.C. Waterfield, H. Binner, G. Griffiths and Maurice Wright
ISHM invites papers for the above Conference, to be held on 29–31 May 1991 in Rotterdam, The Netherlands. Papers should cover areas such as: design, manufacturing, packaging and…
Abstract
ISHM invites papers for the above Conference, to be held on 29–31 May 1991 in Rotterdam, The Netherlands. Papers should cover areas such as: design, manufacturing, packaging and interconnection, materials and processing, applications, reliability, components, new technologies, marketing and economics, optoelectronics. Summaries should be in English, length 200–300 words. The deadline for receipt of summaries is 30 September 1990. (For full details, see announcement on pp. 54–55.)
This event, the first sponsored by ISHM, takes place in Pardubice on the 19–20 November 1991. Pardubice is a town of some 100,000 inhabitants about 60 miles east of Prague. A…
Abstract
This event, the first sponsored by ISHM, takes place in Pardubice on the 19–20 November 1991. Pardubice is a town of some 100,000 inhabitants about 60 miles east of Prague. A welcome is extended to all ISHM Chapter members.
L. Halbo, C.W. Nielsen and S. Nørlyng
The paper gives design guidelines for polymer thick‐film technology (PTF). After an introduction reviewing the main PTF properties, materials and processes, detailed PTF design…
Abstract
The paper gives design guidelines for polymer thick‐film technology (PTF). After an introduction reviewing the main PTF properties, materials and processes, detailed PTF design rules are presented. They are conservative, to achieve high production yield. The design rules are based on the considerable experience in the companies of the authors and of the persons mentioned in the acknowledgements, as well as on information from the open literature and from materials suppliers. The design guidelines are intended primarily for designers, but they are also important for production personnel, to facilitate a close coupling between design and production, and thus provide optimum use of PTF and obtain high production yield.
Robert Blancquaert, Miloš Somora, M.S. Vijayaraghavan and D.J. Lowrie
ISHM‐Benelux has recently set up a permanent secretariat at the following address:
Abstract
Details
Keywords
Two members of ISHM‐Hungary, Professor Zsolt Illyefalvi‐Vitéz, ELC representative, and Professor Gábor Harsányi, president and TPC representative, attended the NATO Advanced…
Abstract
Two members of ISHM‐Hungary, Professor Zsolt Illyefalvi‐Vitéz, ELC representative, and Professor Gábor Harsányi, president and TPC representative, attended the NATO Advanced Research Workshop on MCM‐C/Mixed Technologies in Florida, USA, in May co‐sponsored by ISHM‐US and organised by: