Active PCB

 

Prototype and Production PCB's That Meet the Rohs Directive

Active Sales is currently producing both Prototype  and Production 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 diphenyl ethers. We are using raw materials and processes that enable us to meet those restrictions.

Active Sales 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.

It is not Active Sales' intent to replace our tin lead solder process at this time. It will continue to run in tandem with the lead free process until the use of leaded solder becomes untenable.

ENIG and Immersion silver were added to our "in-house" capabilities many years ago. We are now able to offer electro-less nickel immersion gold plating as an alternative to the lead-free solder finish. Immersion silver was included in our new immersion plating line so we have yet another "in-house" option for a final plated finish.

RoHS Compliant

Currently any printed circuit board that we produce does not contain any mercury, cadmium, hexavalent chromium, polybrominated biphenyls or polybrominated diphenyl ethers. 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, electroless nickel immersion gold, immersion silver, electroplated gold, white tin or finishes other than tin-lead solder.

Laminates

Active Sales 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.

Active Sales has UL approval for processing high thermal capacity materials manufactured by Isola/Polyclad and Nelco among others. These materials met the UL testing for 130 degrees C maximum operating temperature, solder limits of 288 degrees 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 4101B specification sheets 26, 28, 121, 124 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 Active Sales sales representative.

Lead Free Solder

Active Sales installed a new Lead Free HASL machine 2007 to run lead-free solder. We are using SN100 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.

Electroless Nickel Immersion Gold

A combination plating line for electroless nickel immersion gold and Immersion silver was installed at ASA Taiwan facility. The electroless 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 to 8% P, too low would easily corrode/too high makes subsequent soldering of parts more difficult.

Immersion golds are replacement chemistries.  This means that they attach themselves 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 such time as it is soldered to. The recommended gold thickness is 2 to 4 micro inches. As the purpose of the gold layer is to maintain the solderability of the nickel surface, it is necessary that it be thin (two to four micro inches is preferred) 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. Immersion silver processes available in the industry co-deposit 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. This makes this process very conducive to conveyorized processing. IPC specification 4553 covers Immersion silver and when issued will specify 8 to 12 micro inchess 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 the ground plane areas.

The primary use of IAg is as a solderabilty preservative. During assembly the immersion silver dissipates into the solder and allows the formation of a Cu/Sn intermetallic. All indications are that IAg will transition readily into LF assembly. This is to be expected since the SAC alloy contains a relatively high percentage of silver.

Electrolytic Nickel Gold

Electrolytic plating of gold over a nickel base, commonly referred to as hard gold, is also available from Active Sales 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.

 Lead Free Assembly:

The use of Lead-free solder paste requires increased temperatures in the assembly process. As such, we should be concerned with three different laminate characteristics Tg, Cte, and Td.

1. What is Tg? Transition of glass - this is the temperature the glass strands in the material go from a solid to a semi fluid state.
2. What Tg materials are required? This depends on the thermal profile of the assembly process. We offer a range of Tg ratings from 150

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