Three  years ago a survey was conducted by the SMART Group of 250 printed board
suppliers on their current and preferred solderable finish for surface mount
boards. The results are included here for your reference. The survey is now
being repeated to also cover the cost associated with different solderable
finishes. A survey also conduct three years ago considered the cost of printed
board manufacture based on a standard model, the results are also included here.

Next week a new survey will be posted on the Internet examining the trends in
different solder finishes and the cost associated with them. If you are a PCB
manufacturer and found the information here of value then please take a couple
of minuets to complete the next questionnaire and return next weeks Email. The
final results will be circulated to all contributors. The more contributors the
more accurate incite will be obtaining on the current trends on alternative
solderable finishes. Remember that 500 SMART Group member companies in Europe's
largest Trade Association are interested in solderable finishes and improving
their assembly yields.

Bob Willis
SMART Group

SMART Group Survey Results

To provide further information on the European market for alternative finishes a
brief survey was circulated to the 215 UK printed board manufacturers listed by
Technical Reference Publications. The survey was also circulated to eight
companies in mainland Europe. From the 223  forms circulated a total of 41 were
returned after completion. Most of the responses were from UK companies with
only three returned from Europe.

The manufacturers were first asked which solderable finishes do they currently
offer their customers for surface mount products. The most widely offered finish
was solder levelled 24% with traditional tin/lead reflow 22%. Gold over nickel
was offered by 17% of the companies.

Other finishes which were offered for surface mount boards were immersion tin,
roller tin, nickel, horizontal levelling, bare copper with no protective coating
and solder paste and reflow. Only one or two companies offered any of these
alternatives. Two of the suppliers offering these alternatives were involved in
flexible circuit manufacturer.  

The printed board manufacturers who responded indicated that in terms of volume
of boards or square inches solder levelling was the most often specified finish
69% followed by traditional tin/lead finish 26% and organic coatings 5%. 

The solder levelling process was indicated by 52% of the companies as offering
the best compromise between the requirements of the assembler and the ease of
fabrication. There was very little difference between the three other finishes
tin/lead reflow, gold over nickel or organic coatings.

In terms of popularity with customers the following finishes are being  most
often requested for surface mount products. The finishes are listed in order of
popularity. 

1.	Solder Levelling
2.	Tin/Lead Reflow
3.	Gold over Nickel 
4.	Brushed Tin/Lead
5.	Organic Coating (Entek, Glicoat T)
6.	Flux Lacquer Coating (Different Manufacturers)

The difference in solder finish costs below are based on the following model.
The model printed board for cost calculation is a double sided board produced
from FR4 laminate incorporating surface mount pads down to 0.025" pitch on both
sides. The board size is 6.28" x 8.95" with photoimagable solder resist on both
sides and silk screen legend on one side. There are 2368 holes, four different
sizes the smallest being 0.018". Track size is 0.006" with 0.008" spaces. An
estimate of 20% should be used for open copper areas requiring the solderable
finish. The price should be shown for a single batch of 500 and a 1000 boards
with the tooling costs.

Copper protective finish
500 PCB's L8.84 each
1000 PCB's L8.28 each
Hot air levelled
500 PCB's L9.44 each
1000 PCB's L8.85 each
Nickel/gold
500 PCB's L9.51 each
1000 PCB's L8.95 each

One off:
Tooling cost L426
Electrical test fixturing L550

Remember that next week we will be circulating the new survey so please
contribute to the leading Surface Mount Association and be SMART.

Bob Willis
Tel: (44) 01245 351502
Fax: (44) 01245 496123
Home Page: http://ourworld.compuserve.com/homepages/bwillis
Email: [log in to unmask]