you said:
>Be careful in price comparisons when concerning OSP's. Unlike metallic
>finishes, its price is frequently figured for board surface square feet(6'
>for 18"x24")due to relatively high dragout losses, not finished square
>feet(in most cases, <3').
Interesting. So I infer this: If I have a 10" x 7.2" PWB design to be
fabbed as 4-up on an 18" x 24" panel, each unit represents 72 sq inch per
side, 144 sq in both sides.
>There are definite benefits in processing for the board shop. It is
>possible, not recommended, to re-work the product forever, or until you
>(10's of microinchs a time) etch your copper below spec.
>
>Additionally, since it is recommended as the final step prior to bagging,
>images are processed as images, not panels of 4 of more(for other methods).
>With every extra image per panel, handling at the board shop will increase,
>causing non-material operating costs to increase.
I guess you mean image = unit...
So, is the cost estimated based on the panel area, or the unit area? That
would be 6 square feet (both surfaces) for the panel, or 4 sq ft for the
four units...
>Once ALL costs are figured, OSP's could be equal to (or better than) HASL
>dollarwise (depending on product). They do seem better environmentally and
>have much better planarity than HASL, but I do not think it will warrant
>cost reduction until it replaces HASL as a board shop's primary
>solderability preservative.
You know, my gut feel is you are exactly right here. Most board shops will
only offer it as a premium until they have it running in quantities, and
until it has gained general acceptance with big OEM's, or IPC has a spec
covering it, or the EPA mandates it...
My own opinion is that OSP is a good process, and probably will eventually
be very popular. It brings to mind how long it took for SMOBC to really
"take over" from subtractively processed tin-lead plated boards (when
everybody in the industry know it made sense).
>Charles Stuber
>Chemical Process Engineer
>Automata
>703-450-2600
>[log in to unmask]
>http://www.automata.com
>
> ----------
>
>From: TechNet-request
>To: rbormann
>Cc: TECHNET
>Subject: cost of OSP vs HASL PWB coating
>Date: Monday, September 11, 1995 5:55PM
>
>you said in your CircuitWorld Sept 95 newsletter:
>
>>Fabrication Costs ... estimated HASL costs $ .75 - 1.00 per square foot
>> estimated OSP costs $ .35 per square foot
>>The costs to the PWB fabricator are significantly reduced and the assembler
>>benefits from increased yields and better product reliabilty.
>
>At the recent Surface Mount International Conference, a paper was presented
>by Ray, Artaki, Wenger, and Machusak of AT&T Bell Labs. They offered the
>following fab cost comparisons ($/sq. ft.)
>
> Imidazole immersion tin HASL Pd/Cu Pd/Ni Au/Ni
>min .020 .75 1.40 1.40 2.30 2.80
>max .050 1.10 2.40 2.40 3.70 4.00
>
>These numbers are actually my interpretation of the graph shown in the
>paper as published in the proceedings.
>
>These figures are a little higher than what your Newsletter showed.
>
>I would interperet that for a typical 3 sq ft panel, the cost savings to
>the fabricator might be 1.90 to 1.20 per sq ft switching from HASL to OSP.
>If that is the case, a 4 unit per panel might cost the fab supplier say
>$0.40 less to produce.
>
>If I knew I could save $0.50 per unit on buying PWB's (as a PWB assembler),
>I would be a hero. To date, no supplier of our Company is offering such
>price reductions. Maybe they will soon, let's hope.
>
>Based on early testing we have done of these coatings, I am ready to change
>when the savings justifies the relatively minor process changes, but
>probably not until that time.
>
>Jerry Cupples
>Interphase Corporation
>Dallas, TX
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