by Timothy Jensen , Dr. Ronald C. Lasky
Chinese version of Challenges of Implementing a
Halogen-Free PCB Assembly Process.
oxidation barrier, activator, pb-free, reflow, graping, head-in-pillow, halide-free, halogen-free, halogens, CHINESE LANGUAGE
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Posted on 22 Mar 2010
by Dr. Ronald C. Lasky , Timothy Jensen
The electronics industry continues to strive to provide more environmentally friendly products. This movement is partly due to legislation from various countries, partly due to public outcry from well publicized 3rd world recycling practices, and partly due to non-government organizations (NGOs) testing and publishing information on electronic devices regarding their content of various toxic materials. One set of materials targeted for reduction and eventual elimination are halogenated compounds. Halogens are found in plastics for cables and housings, board laminate materials, components, and soldering fluxes. Replacing these halogenated compounds can have a dramatic affect on the PCB
assembly process. In this paper those challenges will be discussed as well as techniques and practices that will help ensure high end of line yields and continued reliability.
oxidation barrier, activator, pb-free, reflow, graping, head-in-pillow, halide-free, halogen-free, halogens
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Posted on 4 Mar 2010
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
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Posted on 14 Oct 2011
