RHF stands for RoHS Halogen Free. NXP introduced the RHF-2006 indicator to identify compliancy and it is used on many parts in the marking of commercial products and on their packing labels. RHF-2006 identification codes are as follows:

RHF-2006 indicator Description
Dark Green = Indicates products that fully comply with the EU Directive 2011/65/EU (RoHS) without exemptions and halogens and Antimony Oxides.
Green = Indicates products that fully comply with the EU Directive 2011/65/EU (RoHS) without exemptions, but containing halogens and/or Antimony Oxides.
Halogen and Antimony Oxide-Free, Leaded = Indicates products that comply with the EU Directive 2011/65/EU (RoHS) with exempted Lead, but Halogen and Antimony Oxide Free as well.
Exempt, Leaded = Indicates products that comply with the EU Directive 2011/65/EU (RoHS) with exempted lead, and also containing halogens and/or Antimony Oxides.
Non-EU/CN RoHS compliant = Indicates all non-RoHS compliant products, whether or not they contain halogens or Antimony Oxides. This includes products with lead in the outer terminals, such as QFP with traditional SnPb plating, and BGAs with SnPb balls.

For More Information visit the Environmental Compliance Organization.