Halogen-Free Assembly Blog

By Tim Jensen

The IPC J-STD-004 committee met at APEX last month. They are planning on releasing an updated specification. One positive change that is being made is that titration is being eliminated as an acceptable method for quantitative halide analysis. That means that ion chromatography is the only acceptable test method for quantitative halide analysis per J-STD-004. You can find this test method on the IPC website at: Ion Chromatography Test Method 2.3.28.1

The J-STD-004 requires that a flux be less than 500 ppm of total halide (Cl+Br+Fl+I) to be classified as L0 (which is often used synonomously with halide-free). The challenge is that only ionic halides are detected with ion chromotography. As I have stressed before, L0 or halide-free per J-STD-004 is not necessarily halogen free.

The committee agreed to include a note in this revision of J-STD-004 that this test method should not be used to test for total halogen content. Although I would have preferred replacing the current test method with the oxygen bomb combustion & IC method for detection of halogens, I feel this is a step in the right direction.

We are getting closer to the goal of everyone undertanding what “halogen-free” really means! Baby steps!

When testing a solder paste or flux for halogen content, it is still up for debate as to whether or not the sample should be reflowed prior to testing. Those looking to assemble halogen-free electronics are interested in what remains on the board. Therefore, it makes sense to test the residue for halogen content.

Unfortunately, reflowing the material does make the testing more difficult. The reflow profile used could impact the halogen content. Leaving this open for interpretation may allow for the use of an unrealistic profile to make the halogen content of a material appear better or worse. Also, the process of scraping up the residue to prepare for testing allows for contamination.

Indium Corporation would prefer to see a standard developed to be able to perform a halogen test on the raw flux rather than residue. However, this would require some correlation between the raw flux and what would actually appear in the residue. The adjacent figure shows testing of a flux before and after reflow. As expected, after reflow the halogen content appears higher because all of the solvents in the flux have volatilized. In the coming weeks, we will try to correlate the before and after reflow halogen values to the volatility of the flux (through TGA analysis). If a correlation exists, then we will test it on other materials to attempt to validate this correlation.

I was at the IPC APEX convention last week and attended the IPC J709 Halogen-Free Electronics Task Group meeting on Monday March 31st. There were well over 100 people attending this meeting. That is almost an order of magnitude more than what I typically see at an IPC Task Group meeting (just another confirmation that this halogen-free thing is the real deal). The two biggest challenges facing the group are (1) how to define “halogen-free” and (2) what are the maximum acceptable limits of those halogens.

Does halogen-free include all of the halogens or just Cl and Br? Should it just include CFR’s (chlorinated flame retardants), BFR’s (brominated flame retardants), and PVC (polyvinyl chloride) because these are the compounds being targeted by environmental organizations? Are the 900ppm Br, 900ppm Cl, and 1500 ppm total limits that are established for PCB’s suitable for all electronics parts and materials? These are some of the questions that the large group discussed (and often disagreed on) as the group looks to create a clear message for the industry.

In the end, the most notable accomplishment was the agreement to develop a tiered approach to defining and testing for halogens. Initially, there will probably be four groups (or classes) of halogen-free which will become increasingly more accurate and difficult to comply with. The fundamental approach is something like this:

Class 1 (easiest): Restriction of PVC, BFR, and CFR using the already established 900/900/1500 limits.
Class 2: Restriction of elemental Br and Cl using the already established 900/900/1500 limits. However, there will be an exempted list of materials.
Class 3: Same as Class 2 without any exemptions.
Class 4: Restriction of all halogens (Br, Cl, Fl, I) using a maximum of “none detected” as defined by equipment capabilities

Of course, this is all subject to change based on the input of the group!