Ask the Experts
August 8, 2018
Bromine Free PWBs
What are the pros and cons of bromine in PWBs?Several of our customers require bromine free PWBs, but some of our suppliersdo not think that is a good way to go. Are bromine and lead free connected?
Expert Panel Responses
Bromine complexes,primarily tetrabromobisphenol-A (TBBA), has been used as a flame retardantmaterial for many years in laminate materials. The FR in FR4 stands forFlame Retardant. Many epoxy laminates have this material bound into thechemical matrix.
The move tohalogen-free materials is the result of fear-mongering, science hating, groupswhich deem all halide materials as bad. Consequently, much environmentallegislation is aimed at reducing halides in laminates.
The pros of bromineadditives: they work, they are chemically stable, and they are not ahazard to the environment or the people who work with them, at least inlaminate form. The cons relate more to those workers in the chemicalindustry who deal with high concentrations of bromine.
Halogen-freelaminates (which are not really halogen free) use alumina or magnesium salts toreplace the bromine compounds. They are not as effective as thebrominated compounds, and result in other undesirable effects, such as padcratering.
I would go back toyour customer and ask why they require bromine-free PWBs? Is it aregulatory/legal requirement, or are they just jumping on the halogen-freebandwagon?
Principal Materials and Process Engineer
Doug Pauls has a bachelors in Chemistry & Physics, Carthage College, BSEE, Univ of Wisc Madison. He has 9 years working experience for US Navy - Materials Lab, Naval Avionics Center Indianapolis. 8 years Technical Director, Contamination Studies Laboratories. 11 years Rockwell Collins Advanced Operations Engineering.
Bromine-freeand Lead-free are connected via the RoHS initiative
Brominatedhydrocarbons such as PBE and PDBE have traditionally been used as flameretardants. The RoHS initiate calls for elimination heavy metals in electronicsessentially banning use of PBE and PBDE.
Bromine-freeis defined as <1,000 ppm or 1,000 mg/KgLead-free is defined as <1,000 ppm or 1,000 mg/Kg
Global Sales Director
Mr. Greenland has 20 years electronics industry experience ranging from circuit board design to product support & repair services. Peter has spent the last 4 years at Pycon Inc. supporting customers that require high mix, low volume manufacturing solutions.
Bromine and lead-free are connected, in some ways,because both are targeted by the RoHS legislation. Bromine itself it not specifically targeted, but there are two common Brominated flameretardants that are used in circuit boards that are banned by RoHS. As a means of simplicity and ease of testing, many have decided to eliminate allBrominated compounds from circuit boards and other processmaterials. (XRF is commonly used to test for the offending Brominated flameretardants, but XRF can only measure Bromine level, but not specificBrominated chemical compounds.)
As to pros and cons, the pros for the Brominated flameretardants is that they are well established and understood in the marketand carry no price premium. But sincethey are hard to test with existing equipment (again, XRF), they are being banned in favor of Bromine-freevarieties. These Bromine-free flame retardants are not as well understoodin the market, but the learning curve is swift and shouldn't present amajor hurdle. There may be a slight price premium for these changes, soconsult with your board vendors to verify this.
General Manager - Electronic Assembly Americas
Mr. Smith has been supporting customers in the electronics assembly industry since 1994. His expertise is focused on solder paste printing and reducing soldering defects. He holds a BS in Chemical Engineering and an MBA in Marketing. He has authored several papers in trade magazines and at industry conferences. He is an SMTA Certified Process Engineer.
Bromine-free (or more properly known as "Halogen-free" or"Low-Halogen") and Lead-free are not connected. Lead-free requirementsare related to the EU RoHS Directive and the restrictions on the use of lead inelectronics. The push to eliminate halogens (specifically bromine andchlorine) is from OEM customers who are getting pushed by Non-GovernmentalAgencies (NGOs) to make their products more "green."
The definition of "Low-Halogen" for Printed Boards is containedin IPC-4101 (see the latest revision), and is defined as:
These concentration limits apply at the homogeneous materiallevel, which means the resin used in the laminates or prepreg. If ananalysis of the halogen content is made, only the resin should be used - notthe fiberglass reinforcement or the cladding. As an aside, there is anIPC committee working on a guideline to define "low-halogen" for materialsother than Printed Board (IPC-4903). This guideline should go out forcomment in the next few months.
Most of the laminate and prepreg suppliers in the industry dohave low-halogen products. These products may be based onbismaleimide-triazine or other resins that use metal hydroxides for flameretardancy. The processing characteristics of these prepregs andlaminates will probably be different than the brominated epoxies used by therequester. Companies switching to halogen-free materials should workclosely with their suppliers to characterize the process for manufacturingPrinted Boards using the new materials.
A great place tolearn more about this issue is the IPC webpage on Halogen Free and BrominatedFlame Retardants at: http://www.ipc.org/ContentPage.aspx?pageid=Halogen-Free-and-Brominated-Flame-Retardants.
- Less than or equal to 900 ppm Bromine, and
- Less than or equal to 900 ppm Chlorine, and
- Less than or equal to 1500 ppm combined Bromine plus Chlorine
Corporate Product Compliance Manager
TriQuint Semiconductor, Inc.
John has focused on Product Compliance and Environmental & Safety issues throughout his career. He has a B.S. in Chemical Engineering, an M.S. in Chemical Oceanography, an M.S. in Environmental Engineering, and is a Professional Engineer in the fields of Chemical and Environmental Engineering.
Mostencapsulent materials previously contained Bromine( halides) as a fire retardant filler. New "Green' materials contain no Bromine containingcompounds. In general they have been an improvement and copper ball bondingactually has better reliability with specifically formulated (for copper)"Green" encapsulents.
Process Solutions Consulting Inc.
Lee Levine has been a Process Engineer and Metallurgist in the semiconductor industry for 30 years. He now operates his own company Process Solutions Consulting Inc where he consults on process issues and provides SEM/EDS and metallography services.
I am not a PWB expert but the low halogen push is from NGOs (nongovernment organizations) push to remove the BFR and CFR types of flame retardants.They demonstrated electronic products are being burned to gather themetals out of them in improper recycling (open pits) processes by kids andolder folks that is very harmful to the people and environment. Ifrecycled properly, this is not an issue. These materials are definitely agreat benefit for the products they are used concerning flame retardency. There are no laws banning their use, but it is an industry push to be "greener"from mostly OEMs being pressured by NGOs. The OEMs in turn have putpressure on the supply chain and several have it written in the contracts /stated on their websites that their products are low halogen.
Are bromine and lead connected? Yes, both are (were) commonlyused in electronic PWBs / components and were safe for use. Both are/werethe lowest cost solutions. Changes to both have costs millions(billions?) to replace. Cost increases include
Is it a good way to go? That remains an open debate.
- Research and development along with material changequalifications and approvals up and down the supply chain
- The continued cost for replacement materials being greaterand
- The energy use has increased because of reflowtemperatures being greater than what has been traditionally used (from 220C - 235C to 260C as seen in J-STD-020D).
Product Stewardship Management
Mark Frimann has been working in electronic industry regulations and standards on chemical and material restrictions, and how this is dealt with in the supply chain, and addressing on-going issues as these requirements change and become further defined.
Bromineand lead free are both pseudo environmental specifications forelectronics. Lead was required to be eliminated in electronics by theEuropean Union RoHS Directive and other similar regulations because of (unproven)concerns regarding potential human exposure to the lead in electronics. Although there are no laws requiring removal, some OEMs are specifying brominefree electronics because of environmental concerns related to dioxin formationduring improper combustion of waste electronics. The main use of brominesin circuit boards if for flame retardancy. Removal of bromine requiresthe use of other flame retardants which can affect certain performanceparameters and price.
Director, Government Relations and Environmental Policy
Fern Abrams is the Director of Government Relations and Environmental Policy for IPC. She is responsible for advocating member positions in the areas of environment, health and safety, tax, trade, intellectual property and other regulatory issues. Current activities focus on conflict minerals regulations; implementation of best practices for protecting intellectual property, research and development tax credits, international materials restrictions, hazardous waste, and environmental reporting and record keeping.
The idea that any chemicals are free from heath hazards is erroneous. Even too much water can cause harm.
Tony Stanley, Tyco Security Products
The major change in the EU was the introduction of Reach where the target is to register all chemicals and put the onus on the manufacturer to prove that they are safe with biology.
The term hazardous tends to refer to a more immediate hazard, rather than the less well studies harm to reproduction, cancer or other sensitive membranes. You need to be very careful assuming that any chemical does no harm. The position on each chemical is changing on a regular basis.
What Halogen Free is or is not is well covered by the experts so far. Missing in the discussion is the impact of Halogen Free on signal integrity. HF materials tend to have higher Dk or dielectric constant which may have a negative impact on your impedance. This is especially true if you have limited space for routing. DF or loss values tend to benefit from halogen replacements.
Steve Ethridge, Dell Technologies