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