American Circuit Technology and its Lead-free finish plating

American Circuit Technology, a Printed Circuit Board manufacturer, is rapidly developing to keep pace with today's new Computer technology demands. One of its new and exciting innovations is the creation of reliable surface plating for Printed Circuit Boards or PCBs, an electronic card used to connect electronic components to one another. 

The manufacturing of electronic devises is governed by the 2003 regulations of the European Union known as the RoHS or Restriction of Hazardous Substances. On July 1, 2006, in compliance with the RoHS regulations, the European Union restricts the use of lead and other hazardous materials in the manufacturing of all electrical and electronic equipments. This improves the quality of the finished PCBs and decreased the probability of lead contaminants in the environment.

Being the cutting edge in the Printed Circuit Board manufacturing industry, the American Circuit Technology takes pride in its high-quality and lead-free finish products long before July 01, 2006.  At present, it still continuously complies with the RoHS directive to develop and deliver lead-free products to lessen the hazardous impact in the environment.

Besides not using lead in their manufacturing process, the company makes printed circuit boards without using cadmium, hexavalent chromium, mercury, polybrominated biphenyl(PBB), and polybrominated diphenyl ether (PCDE).  Below are the three types of lead-free Printed Circuit Board finish manufactured by the American Circuit Technology:

First Finish: Electroless Nickel Immersion Gold (ENIG)

This kind of surface plating has been reported by National Circuits Inc. to meet the RoHS standards because of its lead-free components. This resolution has made the Electroless Nickel Immersion Gold (ENIG) the primary form of electronic plating available in the market and is now being widely used by most computer and electronic items manufacturers due to its primary characteristics of versatility, durability, longer shelf life and excellent electrical continuity due to its gold topcoat.

The versatility of Electroless Nickel Immersion Gold (ENIG) is determined by its capability to be assembled in different ways like below:

• Wave soldering (soldering the components to the PCB to form an assembly).

• Wire bonding (connecting the integrated circuit to the PCB during the semiconductor device fabrication process).

• Solder fusing.

The durability of the Electroless Nickel Immersion Gold (ENIG) lies in its structures and its physical composition:

• The flat surface provided by ENIG do not tarnish or lose its color due to the presence of a gold deposit that protects the nickel from the effects of oxidation, thereby preventing corrosion, which is most likely to begin on discontinuity sites in metal.

• The nickel prevents the copper from contaminating the solder.

• Phosphorus is combined with the nickel to further increase resistance to corrosion where it is most likely to begin on discontinuity sites in metal.

Second Finish:Immersion Silver (IAg)

The Immersion Silver finish is thinner than Electroless Nickel Immersion Gold (ENIG) or the traditional Hot Air Solder Leveling or HASL finishes making it more ideal choice in terms of performance.

This product has been well established in the industry, but had to overcome some big challenges during its introduction until American Circuit Technology studied and understand its handling, packaging and storage and brought this product to its full advantageous performance.

Immersion Silver can help make the transition into a lead-free assembly due to the fact that the SAC alloy contains a high amount of silver.

Structures and physical composition of Immersion Silver Finish:

• Silver is deposited directly onto a copper surface by utilizing a chemical displacement reaction that makes it work fairly rapidly without requiring high temperatures necessary for Electroless Nickel Immersion Gold. 

• The silver integrated in this finish acts as a preservative. During the assembly process, it is made into a solder which allows it to form into a Cu/Sn inter-metallic (IMC) layer. This product is used as an active surface which can readily be combined with sulfur. One helpful hint about this process is that adding anti-tarnish can help protect the surface from the environment around us.

• Its application is highly specific, and requires specialized equipment such as an X-Ray Fluorescence (XRF), while also considering that proper set-up is crucial for the best results.

Third Finish: Hot Air Solder Leveling (HASL)

Hot Air Solder Leveling or HASL was manufactured since the use of the tin-lead alloy was discontinued by RoHS regulations due its high lead content.

Structures and physical composition of Hot Air Solder Leveling

• HASL Finish process fully wets the copper of the PCB and creates half the soldered joint by using SN100CL, an alloy composed of tin (99.3%), copper (0.7%), and nickel (0.05%) with 60 ppm germanium. Previous soldering processes were composed of a tin-lead alloy.

• Hot air leveling is performed in horizontal or vertical mode after dipping a PCB into a soldering bath. Horizontal process gives a lower thickness of soldering than the vertical process of hot air leveling.

• The excess soldering is removed by a stream of hot air on both sides of the board. When a circuit board is submerged into a soldering pot, the tin and nickel exchange with the copper on the surface resulting in the creation of an inter-metallic (IMC) layer from a dual layering of Cu6Sn and Cu6Sn5. The advantage of this process is the creation of a reliable solder which performs well under reflow and heat cycles. The IMC layer proved to withstand long periods of excessive heat temperatures of more than 500 degrees F (260 degrees C), making it ideal for electronic circuitry.