by Gordon Clark, Renee Michalkiewicz, Timothy Jensen , Brian Toleno, Jasbir Bath
Over the last few years, there has been an increase in the evaluation and use of halogen-free soldering materials. In addition, there has been increased scrutiny into the level of halogens and refinement of the definition and testing of halogen-free soldering materials. The challenge has been that there has been no common standard across the industry in terms of halogen-free definitions and the corresponding test methods to determine these. This has created confusion in the industry as to what end users want and what soldering materials suppliers can actually provide. This paper will review the status of both halogen-free and halide-free in terms of definitions, test methods and the limitations and accuracy of test methods used to determine if a soldering material is halogen/halide-free or not. For halogen-free and halide-free definitions, the paper will review the different industry standards which are currently available and those being drafted, and it will discuss any similarities and differences. It will also cover the origins of some of the definitions mentioned in the standards. The paper will include a review of the accuracy and limitations of several test methods and preparation techniques for halogen and halide determination.
Apex 2011, soldering materials, halides, halogen-free
[Permanent Link to this Paper ]
Posted on 11 Apr 2011
by Nicole Palma, Dr. Ronald C. Lasky
With the advent of RoHS and WEEE and the concern of some companies to eliminate halogen-containing compounds from their products, it is vital to have an understanding of halogen compounds and how to detect them. Halogens are a series of nonmetal elements from Group 17 in the periodic table. These elements are fluorine, chlorine, bromine, iodine, and astatine. A halide ion is a halogen atom bearing a negative charge. Halides can be part of the flux activator system that aid in oxide removal in either a solder paste or flux for wave soldering.
Halide content can be determined by qualitative or quantitative tests. The silver chromate method is a quick and inexpensive qualitative test method used to determine halides in a flux. This test is performed by placing the flux on silver chromate test paper. The halides in the flux react with the silver chromate and produce a characteristic color change on the test paper. A quantitative measure of halides is done by ion chromatography. This quantitative test is quite expensive and time consuming.
Test methods have also been developed to determine the activity of the fluxes in solder paste and wave solder. Most commonly used are the copper mirror and surface insulation resistance (SIR) tests. Copper mirror testing determines the activity of the flux by the effect the flux has on bright copper mirror films, which have been vacuum deposited on clear glass. Based on J-STD 004B, the flux can be classified based on its activity levels as determined by this test.
SIR is an electrical test that measures a change over time in the electrical current between electrodes on the surface of a PCB. It is performed at high temperature and humidity levels, typically 85°C and 85% RH. Ionic residue, left on the PCB after reflow from flux activators, may cause low (i.e., poor) SIR readings.
This paper will discuss the theories behind these test techniques, their differences, and how the presence of halides in the flux activators will affect the SIR and copper mirror results.
Apex 2012, silver chromate, flux, copper mirror, SIR, halides, halogens, ion chromatography
[Permanent Link to this Paper ]
Posted on 14 Oct 2011
