Ask the Experts
December 14, 2022 - Updated
March 11, 2012 - Originally Posted

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 suppliers do 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 retardant material for many years in laminate materials. The FR in FR4 stands for Flame Retardant. Many epoxy laminates have this material bound into the chemical matrix.

The move to halogen-free materials is the result of fear-mongering, science hating, groups which deem all halide materials as bad. Consequently, much environmental legislation is aimed at reducing halides in laminates.

The pros of bromine additives: 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 chemical industry who deal with high concentrations of bromine.

Halogen-free laminates (which are not really halogen free) use alumina or magnesium salts to replace the bromine compounds. They are not as effective as the brominated compounds, and result in other undesirable effects, such as pad cratering.

I would go back to your customer and ask why they require bromine-free PWBs? Is it a regulatory/legal requirement, or are they just jumping on the halogen-free bandwagon?

Doug Pauls
Principal Materials and Process Engineer
Collins Aerospace
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-free and Lead-free are connected via the RoHS initiative.

Brominatedhydro carbons such as PBE and PDBE have traditionally been used as flame retardants. The RoHS initiate calls for elimination heavy metals in electronics essentially banning use of PBE and PBDE.

Bromine-free is defined as <1,000 ppm or 1,000 mg/Kg Lead-free is defined as <1,000 ppm or 1,000 mg/Kg

Peter Greenland
Global Sales Director
Photonis USA
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 flame retardants 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 all Brominated compounds from circuit boards and other process materials. (XRF is commonly used to test for the offending Brominated flame retardants, but XRF can only measure Bromine level, but not specific Brominated chemical compounds.)

As to pros and cons, the pros for the Brominated flame retardants is that they are well established and understood in the market and carry no price premium. But since they are hard to test with existing equipment (again, XRF), they are being banned in favor of Bromine-free varieties.

These Bromine-free flame retardants are not as well understood in the market, but the learning curve is swift and shouldn't present a major hurdle. There may be a slight price premium for these changes, so consult with your board vendors to verify this.

Brian Smith
General Manager - Electronic Assembly Americas
DEK International
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 requirements are related to the EU RoHS Directive and the restrictions on the use of lead in electronics. The push to eliminate halogens (specifically bromine and chlorine) is from OEM customers who are getting pushed by Non-Governmental Agencies (NGOs) to make their products more "green."

The definition of "Low-Halogen" for Printed Boards is contained in IPC-4101 (see the latest revision), and is defined as:
  • 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
These concentration limits apply at the homogeneous material level, which means the resin used in the laminates or prepreg. If ananalysis of the halogen content is made, only the resin should be used - not the fiberglass reinforcement or the cladding. As an aside, there is an IPC committee working on a guideline to define "low-halogen" for materials other than Printed Board (IPC-4903). This guideline should go out for comment in the next few months.

Most of the laminate and prep reg suppliers in the industry do have low-halogen products. These products may be based on bismaleimide-triazine or other resins that use metal hydroxides for flame retardancy. The processing characteristics of these prepregs and laminates will probably be different than the brominated epoxies used by the requester. Companies switching to halogen-free materials should work closely with their suppliers to characterize the process for manufacturing Printed Boards using the new materials.

A great place to learn more about this issue is the IPC web page on Halogen Free and Brominated Flame Retardants at:

John Sharp
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.

Most encapsulent materials previously contained Bromine (halides) as a fire retardant filler. New "Green' materials contain no Bromine containing compounds. In general they have been an improvement and copper ball bonding actually has better reliability with specifically formulated (for copper) "Green" encapsulents.

Lee Levine
President, Consultant
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 the metals out of them in improper recycling (open pits) processes by kids and older folks that is very harmful to the people and environment.

If recycled properly, this is not an issue. These materials are definitely a great 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 put pressure 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) commonly used in electronic PWBs / components and were safe for use. Both are/were the lowest cost solutions. Changes to both have costs millions(billions?) to replace. Cost increases include
  1. Research and development along with material change qualifications and approvals up and down the supply chain
  2. The continued cost for replacement materials being greater and
  3. The energy use has increased because of reflow temperatures being greater than what has been traditionally used (from 220C - 235C to 260C as seen in J-STD-020D).
Is it a good way to go? That remains an open debate.

Mark Frimann
Product Stewardship Management
Texas Instruments
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.

Bromine and lead free are both pseudo environmental specifications for electronics. Lead was required to be eliminated in electronics by the European 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 bromine free electronics because of environmental concerns related to dioxin formation during improper combustion of waste electronics.

The main use of bromines in circuit boards if for flame retardancy. Removal of bromine requires the use of other flame retardants which can affect certain performance parameters and price.

Fern Abrams
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.

Reader Comment
An electronic product has an entire lifecycle that includes end of life disposal. The RoHS directive in the EU was a sister directive to a waste disposal directive for this reason. To make the end of life phase less harmful it was deemed necessary to restrict heavy metals, and certain bromines, which in acid conditions (such as unlined landfill site or uncontrolled disposal) it was feared the heavy metals can contaminate groundwater (especially due to disposal in unlined or unmanaged landfill sites acid conditions causing heavy metal to leach out).

The bromines also convert to hazardous by products (ironically for flame retardant) when the waste product is incinerated (it used to be common to grind circuit boards and incinerate for energy recovery). The limitations imposed by laws (lead and certain specific bromines / halides) and industry limits (low halogen standards) are therefore primarily due to risks relating to the end of life disposal phase of a product lifecycle.

Substances required to be restricted may make recycling more hazardous for workers, but mainly they may enter ecological systems due to inappropriate disposal methods and cause harm once the chemicals break down and enter water, air, soils / food chains, etc. This has been scientifically studied and reported by official bodies as well as by NGOs. See also (UK) Institute of Physics article on the subject of e-waste and their conclusion recommends using safer materials in the products
Carol Ann Cooper

Reader Comment
The idea that any chemicals are free from heath hazards is erroneous. Even too much water can cause harm.

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.
Tony Stanley, Tyco Security Products

Reader Comment
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

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