Lead Free Circuit Boards
We can provide you with UL approved circuit boards with a variety of final finishes that meet the requirements of RoHS, REACH and Conflict Metals regulations.
Since the adoption of the RoHS directive, two additional regulations have been enacted that have had a significant effect on the printed circuit board manufacturing industry; REACH by the EU and the Conflict Metals initiative in the USA. RoHS has matured through the last few years and the majority of the concerns voiced early on have not materialized. Similar legislative action has taken place in the Asian Pacific region including China and Japan among others. In the US, California has restricted the sale of electronic devices that do not meet the RoHS directive.
RoHS or the restriction of hazardous substances focuses on the use of six specific substances; Lead, Mercury, Cadmium, Hexavalent Chromium, Polybrominated biphenyls and Polybrominated diphenylether. The last two are fire retardants used in several types of plastic. The amount of each substance used in a product is limited to a maximum concentration based on the weight of homogeneous material used in a product.
The EU’s REACH or Registration, Evaluation and Authorization of Chemicals program is primarily directed at European manufacturers and importers of chemicals. The aim is to have each chemical registered with the European Chemical Agency (ECHA) and evaluated for its effect on the environment and the population. However, it also encompasses “articles” that are exported to or manufactured in the EU. It forces the producer or importer to register any substances of very high concern (SVHC) that might be contained in the article. The number of pre-registered substances exceeds 140,000, but the number of substances on the candidate list totals just 53 as of this writing. As time goes on the candidate list will expand forcing regular evaluations of articles that might contain the newly added substances. Obviously that includes the evaluation of PCB manufacturing materials and processes to verify conformance.
Conflict Metals, or more correctly The “Conflict Minerals Law” was signed in July of 2010 and speaks specifically to a short list of minerals mined in the region of the Eastern Congo. The list includes the ores that are refined to make tantalum, tin and tungsten as well as gold. The issue here is the source of the minerals rather than a complete ban on their use. Materials found to be sourced from the ore or refineries in the Eastern Congo must be reported as such. This is basically a supply chain traceability issue for board manufacturers, who must now query their suppliers and vendors on the origin of tin and gold used in manufacturing.
Advanced Circuits will continue to monitor changes and additions for each of these regulatory statues and laws. We have been in contact with our suppliers and vendors regarding RoHS, REACH and Conflict Minerals requirements. All of them have responded with statements of conformance in regard to each. The following information is specific to providing our customers with RoHS compliant products. It outlines options and provides information related to producing PCBs that meet the needs of our customers and the RoHS directive.
Our RoHS compliant boards are produced using laminate materials of varying decomposition temperatures with a number of different final finishes. We can provide you with a lead-free solder finish using SN100CL – a lead free alloy of 99.3% tin/ 0.6% copper with a trace of nickel. It is an alternative to more expensive finishes and makes a flatter pad than its leaded counterpart. We can also finish plate your boards with either electro-plated nickel/gold, electro less nickel immersion gold or immersion silver.
The laminate materials that we are processing RoHS products on are capable of withstanding temperatures between 260º and 288º C for 20 seconds or more depending on the laminate selected.
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- Click Here to read an article written by our lead-free expert
Standard and Custom Spec PCB's That Meet the RoHS Directive
Advanced Circuits is currently producing both Standard and Custom Spec PCB's that meet the RoHS Directive. To reach that goal it is important that our circuit boards not only be lead free but also meet the restricted concentration levels for mercury, cadmium, hexavalent chromium, Polybrominated biphenyls and Polybrominated diphenylethers. We are using raw materials and processes that enable us to meet those restrictions.
Advanced Circuits is using a Tin Copper alloy as our lead free solder finish. It is Nihon Superior's SN100CL, a solder that has been in use in Asia for a number of years. It is made up of 99.3% Tin, 0.6% Copper and a number of additional proprietary elements including Nickel. We will continue to run leaded solder application until the use of leaded solder becomes untenable.
Currently any printed circuit board that we produce does not contain any mercury, cadmium, hexavalent chromium, Polybrominated biphenyls or Polybrominated diphenylethers. Boards we produce that are not processed using leaded solder for a final finish will meet all of the RoHS' restrictions. These products would include those that have lead free solder, electro less nickel immersion gold, immersion silver, electroplated gold, white tin or finishes other than tin-lead solder.
Advanced Circuits can supply you with a RoHS compliant board using laminate materials that can be matched up with the exposure to high temperatures during your assembly processes. It is important to keep in mind that some lead free assembly processes will require the laminate base material to withstand temperatures in excess of 260 degrees C or 500 degrees F for extended periods of time. To resolve this, we have high temperature laminates in our inventory so that our customers will be able to meet the higher temperature cycling requirements of some lead free assembly applications.
Advanced Circuits has UL approval for processing high thermal capacity materials manufactured by Isola and Nelco among others. These materials met the UL testing for 130°C maximum operating temperature, solder limits of 288°C for 20 seconds, 94-V0 flame rating and direct support of current carrying parts. Each of these laminate systems meets the minimum requirements for IPC 4101 specification sheets 21, 26, 28, 98, 99, 101, 126 or 129. Individual manufacturer's material types may exhibit variations in electrical, thermal and physical properties. Normally a single manufacturer's material will be stocked for use. If you have specific questions please contact your Advanced Circuits sales representative.
Lead Free Solder
Advanced Circuits installed a Penta 580 HASL machine in October 2005 to run lead-free solder. We are using Nihon Superior SN100CL copper alloy solder for this application. We currently process all of our Standard Spec panels using the lead-free solder in addition to the production Custom Spec panels that require it.This particular solder is 99.3% tin and 0.6% copper with a small amount of nickel added. This lead free alloy allows us to process panels at approximately the same temperature as leaded solder. We ran a series of processing tests to assure the best possible coverage and surface characteristics and the results were excellent. We found the coverage to be excellent and the finish has exhibited exceptional co planarity for a HASL process.
We have sample boards available for your evaluation; just contact your sales representative.
Electro-less Nickel Immersion Gold
A combination plating line for electro-less nickel immersion gold and Immersion silver is in use at Advanced Circuits Aurora facility. The electro less nickel is an auto-catalytic process that deposits nickel on the palladium catalyzed copper surface. The process requires continuous replenishment of the nickel ion and the reducing agent. Good process control (constituent concentration, temperature and pH) is the key to a consistent reproducible deposit. It is very important that the nickel be able to plate a surface with consistent phosphorus levels. Most prefer a middle range of 6 – 8% P, too low would easily corrode/too high makes subsequent soldering of parts more difficult.
Immersion gold is replacement chemistry. This means that it attaches to the nickel by replacing atoms of nickel with atoms of gold. The purpose of the immersion gold layer is to protect the nickel surface until it is soldered. The recommended gold thickness is 2 – 4 µin. The purpose of the gold layer is to maintain the solderability of the nickel surface, so it is necessary that it be thin and pore-free.
ENIG is a very versatile surface finish, it is a solderable surface, it is aluminum wire bondable, and is an excellent electrical contacting surface. It has excellent shelf life, in excess of 12 months, and is easy to inspect (visual) and the thickness is easily verified by non-destructive measurement.
Immersion silver is deposited directly on the copper surface by a chemical displacement reaction. The immersion silver process is co-deposit of an organic anti tarnish with the immersion silver. The reaction is fast - approximately 1-2 minutes and does not require the relatively high temperatures of ENIG. IPC 4553 covers Immersion silver and specify 8 – 12 µins on a pad size of 60 X 60 mils or equivalent. The pad size was specified because the thickness of the deposited silver varies with pad size, the smaller pads plate thicker than ground plane areas.
The primary use of IAg is as a solderability preservative. During assembly the immersion silver dissipates into the solder and allows the formation of a Cu/Sn intermetallic bond. All indications are that IAg transitions readily into LF assembly. This is to be expected since SAC alloy contains a relatively high percentage of silver in the alloy.
Electrolytic Nickel Gold
Electrolytic plating of gold over a nickel base, commonly referred to as hard gold, is also available from Advanced Circuits as a final finish.
Copper and gold tend to undergo solid state diffusion into each other and the process is accelerated by increased temperature. Copper on the surface can oxidize resulting in increased contact resistance and copper migrating into the gold can cause the gold to tarnish and corrode. This can be minimized by plating a barrier layer between the copper and gold. Nickel is commonly used as a barrier layer to prevent the gold migrating into the copper. The nickel barrier helps to reduce the porosity compared with plating gold directly over the copper base.
The nickel protective coating provides several benefits. It serves as a backing to the gold for extra hardness as well as providing an effective diffusion barrier layer between gold and copper. The nickel/gold provides a finish that is heat and corrosion resistant, environmentally stable, solderable and durable the nickel under plate enhances the wear characteristics of gold. Traditionally, nickel/gold plating has been applied over copper features used for keyboard contacts, push pads or edge fingers to provide the conductive, corrosion resistant coating. But at higher frequencies the presence of the nickel layer can produce additional signal loss.
Thicknesses in the range of 125 to 150 micro inches of Nickel are typically plated onto the copper followed by 25 to 30 micro inches of gold. This type of gold plating is not recommended for solderable pads although it will work well with aluminum wire bonding. The intention is to cover features that will experience some wear and tear throughout the life of the circuit board. Gold plating over 15 to 18 micro inches will "contaminate" the solder joint and can cause fracturing and joint failures.