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BESTPROTO- Turning Your Prototypes into Products

 

Lead-free surface finishes

 - January-February 2007
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Thanks to all of our customers, vendors and employees for making the first year of BESTProto a success.

The milestones that we achieved during the year include:
  • Being able to now have over 90 different feeders allows us to offer a greater throughput for our customers
  • Bringing several new employees online for greater flexibility in meeting your fast turnaround PCB prototype demands
  • Bringing a cleaning system on line in order to insure the cleanliness of PCBs post processing
  • Bringing solder paste dispensing capacity on line

After the first year of operations we remain committed to being a high quality fast turnaround medium to high complexity PCB assembler of prototypes. In addition to prototypes we have augmented our work in the prototype arena with low volume, higher complexity hand built electronic assemblies.

Since we can perform detailed modifications to the board or it’s components, you can rectify any design/layout problems earlier in the process-allowing you to get to a functional board faster.

Our differentiators continue to be:

  • The ability to get you your first 2-3 boards in a few days
  • The ability to modify the board during the initial board design so that you do not have to "spin" a new board right away. We have PCB repair artisans available through BEST to do this work.
  • We are built for prototype quantity work. We realize that when we get many designs the hardware is really still being "tweaked". We will work with you during this phase when many other assembly service organizations are not set up to operate in this manner.
  • We can take in parts in every form factor-whether they are singles, on tape, in a stick or in trays

Please call us at (847) 797-9250 if we can help you make your deadline for your next PCB proto build.

PCB surface finishes vary in price, availability, shelf life, reliability and assembly processing. While each finish has its own benefits, in most cases, the process, product and environment will dictate the surface finish that is best suited for the application. BESTProto recommends that the end-user, designer, assembler and their PCB supplier work closely together in order to select the best finish for the specific product design.

Immersion Silver
With the pending lead-free legislation impacting PCB manufacturing on a global scale, the immersion silver process is rapidly gaining popularity as the lead-free surface finish of choice. While ENIG presently has a larger market share, over the past 12 months more immersion silver process lines have been installed in PCB facilities than any other finish. Immersion silver has a controlled thickness of 5-12 micro inches and a shelf life of at least 12 months. Silver is compatible with most assembly processes, is cost advantageous, and with its increased popularity, is becoming more commonly available.

ENIG (Electroless Nickel/Immersion Gold)
The ENIG finish has historically been the best fine pitch (flat) surface and lead-free option world-wide. Benefits to this surface finish are; long-term experience/knowledge of the product and excellent shelf life. The typical Nickel thickness is 75 micro inches along with 3-5 micro inches of gold. Disadvantages include; limited availability and higher costs. Also, if the board manufacturing process is not controlled, quality issues such as "Black Pad" may occur.

Immersion Tin
The immersion tin process has also been historically popular. It provides a consistently flat surface approximately 20-40 micro inches in thickness. This finish solders well, and is cost advantageous. However, finished PCBs have a limited shelf life and should be used within 3-6 months. Many PCB manufacturers around the world have this process in place.

OSP (Organic Solderability Preservatives)
OSP's have been around since the 1970's. It is widely believed that IBM was the first major corporation to give this finish credibility. The thickness of the OSP finish is almost unmeasurable (angstoms). The original formulas had a short shelf life of 3-6 months and could only withstand one or two heat cycles. By today's standards, this would be considered applicable only for lower technologies. The latest OSP formulas are far more robust and are designed for lead-free assembly. They can handle multiple heat cycles and have a one year shelf life.

HASL (Hot Air Solder Leveling)
The 63/37 tin lead solder has been the industry-standard since the inception of the original circuit board. If lead-free is not a concern, HASL is a very cost effective, reliable surface finish utilized in the manufacturing of lower technology PCBs. The HASL process can add stress to high layer circuit boards which can cause long-term reliability issues. This added stress, along with uneven solder height on dense SMT or BGA pads, are good reasons to replace HASL. Inevitably, tighter design criteria, advancing technologies, and/or environmental legislation will force the replacement of HASL. There are lead free alloys which can replace the conventional 63Sn / 37Pb solder in this process, but there are still capability limitations that exist within this process.