solder dispencing vs printing

Hi Ian-

check out the ipc.org technet forum archives, there was recently a big thread about this very subject. There are some definite advantages in some situations to dispensing paste.

Bill

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This is my attempt at beating the "Fuzzburg 7" translator used on the SMTnet Forum that mashes everything it sees. Below the next paragraph are three paragraphs,each with a common numering sequence, where each paragraph represents the columns of a table and the numbers representing common rows of a table.

3. Applying Dispenser Technology

As mentioned earlier, both automatic dispensers and printers can be used to deposit SMT adhesive or solder paste on substrates with a relatively high component density. Dispensers are superior to printers in terms of exact positioning and precise deposit volume control. New generation automatic dispensers can be re-programmed for a new product much faster than a printer can be setup. Dispensers do not require the lost time in developing a stencil for new or changed products. If the purchase decision is strictly based on capital, buyers generally choose printers over dispensers. A further comparison of dispensers and printers follows.

Factor 1 Solder paste waste (%) 2 Operator concerns 3 Deposition control 4 Flexibility 5 Material handling 6 Change-over time between products 7 Change over time between materials 8 Solder paste cost 9 New or revised product start-up 10 Specialized knowledge 11 Speed

Dispenser 1 4 2 Very clean, no messStraight forward machine clean-up 3 High control over amount pasteCoplaniarilty issues controllablePaste rheology does not play a large role in dispensingRequires process control to prevent missing dots 4 Allows frequent design changes 5 Nozzles require cleaning 6 Quick as loading another program 7 Quick as loading another programChange syringe and purge 8 Expensive -400 to +500 mesh, negated somewhat by less waste 9 Couple of hours for programming 10 Requires special knowledge to program machine 11 Slower, may loose 70% of tact on fast chip shooters

Printer 1 30 2 Paste is messyStencil cleaning capability requiredWaste disposal requirements similar to other activities 3 Difficult to control amount of pasteStepped stencils can be a nightmareStencil apertures clog with pasteCoplaniarity issues make printing difficultRheology requires constant working of pasteRequires process control to prevent misprints, clogged apertures 4 Stencil(s) required for each production stage 5 Stencil cleaning capability requiredStencils must be stored, maintained, and controlled 6 Stencil, vision system, printer, and substrate must be aligned 7 Stencil, vision system, printer, and substrate must be alignedRequires cleaned-up of previous material 8 Less expensive 9 Hour plus to reduce and adjust apertures, create Gerbers, liaise with suppliers, write purchase orders la di da etc etcStencil foils required for each side and version of product 10 Operators without special skills can setup machine 11 Can be put in front of and use fast chip shooters effectively

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