Halogens and Halides: Consider Halogen-Free Flux and Solder Paste

Part 2 of 2 – The Need for Halogen-Free Materials and the Impact on Your Electronics Manufacturing Process

What will happen if halogen-containing substances are banned from use in electronics manufacturing? It’s important to know your options in terms of sourcing halide- and halogen-free materials for your production process.

In part 1, we discussed what halogens and halides are and why they are a concern in the electronics industry. In part 2, we will discuss the need for halogen-free materials along with the differences between them and what is being used currently.

Should Everyone Switch to Halogen-Free Materials?

Not necessarily since existing regulations aren’t driving the production of halogen-free electronics. While the possibility of future regulation is a factor, corporate responsibility and major multinational companies with halogen-free implementation plans are key drivers in the decision to use halogen-free materials.

The green or eco-friendly social movement is also a factor. Many companies are looking for ways to reduce any negative impact on the environment.

Brominated flame retardants (BFRs) are a major concern despite European studies that suggest most BFRs used in electronics pose no risk to humans or the environment. Persistent constituencies are lobbying otherwise since some lab tests have produced measurable effects given prolonged exposure of BFRs in high dosages.

Depending on what materials you use, there may be no change required. Your process may already be halogen-free. This means your products do not release halogen as a byproduct when disposed of by incarnation. If your facility is not yet halogen-free, you should understand the differences between halogen-containing materials and halogen-free materials.

How are Halogen-Free Materials Different?

The primary replacements for BFRs are phosphorous-based materials. Phosphorous-based chemistries are currently costlier and require close cooperation between material vendors and board fabricators since the process window is smaller.

These materials are typically more hydrophilic, so moisture sensitivity ratings are lower. In most cases, significantly more halogen-free material is required to achieve the same level of flammability resistance. Side effects include shorter shelf life, greater printed circuit board (PCB) stiffness, and lower coefficient of thermal expansion (CTE). On the plus side, some halogen-free laminate systems have greater thermal stability.

Halide-free fluxes are typically less active than their halogenated predecessors. A consequence is that many do not wet as well and have a smaller profile process window. Component lead solderability has a greater effect on joint quality. In addition to changes in the reflow process, migration to halide-free reflow may necessitate other material changes to accommodate the limitations of halide-free flux chemistry.

What’s Next?

While it is still unclear whether regulations will be forthcoming or not, it is worthwhile to understand the differences between halogen-containing and halogen-free materials and to know how to transition to halogen-free production. To be caught off guard by future regulations could disrupt workflow, causing backlog, product loss, and issues with the disposal of unusable material.

For more information, or to access the sources used in this article, download the Halides and Halogens white paper. Contact Nordson EFD at [email protected] if you'd like to learn about our high-quality, ISO-certified halide-free solder paste.