SMTA International Conference Proceedings

Characterization Of Solder Paste Wetting/Spreading Performance – Current Status In International Norms And Standards

Authors: Sebastian Stengel and Prof. Dr.-Ing. Marcus Reichenberger; and Jörg Trodler and Albert Heilmann
Company: Technische Hochschule Nürnberg - Georg Simon Ohm and Heraeus Materials and Technology
Date Published: 10/13/2013   Conference: SMTA International

Abstract: Solder paste is one of the most important materials used in modern electronics manufacturing. Besides its task to provide sufficient solder material to establish a reliable solder joint, prior to melting the solder paste has to maintain defect free printability, tackiness to hold the components in position as well as oxidation protection and oxide removal during soldering.

Although superior wetting characteristics are a crucial precondition for defect free assemblies, currently available international standards do not provide transparent and sufficient guidelines how to qualify the wetting performance of a solder paste. Therefore, both, materials manufacturers as well as electronics assembly companies have to define specific test methods and quality criteria in order to quality the performance of a new solder paste during development, prior to materials introduction or regularly as quality inspection method.

In the paper, the authors develop a comprehensive overview about the available standards and norms regarding the qualification of the wetting behavior of solder alloys, fluxes and solder paste. With specific focus on solder pastes, international (IEC) European (EN) standards as well as Japanese standards (JEITA) and commonly used industry standards (IPC) are compared in terms of test methods, test conditions as well as performance criteria.

As a result, it can be stated that none of the currently valid and reviewed standards addresses the wetting and spreading behavior of solder pastes in a way which is reflecting real use and processing of solder paste in the test conditions. This leads to un-practical test procedures and – what is even more critical – to test results, which do not comply which the real solder paste process performance.

Due to these unfavorable results, it is the author´s aim to develop a new, commonly applicable and realistic test procedure for the wetting behavior of solder pastes. First results of this work will also be presented.

Key Words: 

solder paste, wetting, spreading, wetting balance, slump, test procedure

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