By Les Hymes (auth.), Les Hymes P.E. (eds.)
The impetus to create this e-book originated from numerous matters. this sort of used to be the perceived worth to the of a suite in a single quantity of a variety of details pertinent to the explanations and methods for de fluxing revealed wiring assemblies (PWAs). This booklet is predicted to be of use not just to these engaged within the electronics packaging but additionally to these in comparable fields looking info bearing on plausible equipment of facing one of many en vironmental problems with our time: the destruction of the ozone layer surrounding and maintaining the planet with which we've been entrusted. the amount of data relative to supplying PW As freed from residues advert versely impacting operation, reliability, and lifetime of digital items is develop ing, and it'll proceed to extend at an sped up fee as we search to compare our expertise wishes and needs with our environmental obligations. on the time ofthis writing, which has spanned the latter component to 1989 and early 1990, the problem of selecting a brand new method of generating PW As freed from harmful residues whereas utilizing environmentally applicable production ideas ap peared to be the main difficulty of nearly all of these serious about the published wiring meeting undefined. To many this intended using varied fresh ing media and/or procedure or apparatus improvements; to others it intended the removal of the necessity to fresh via fabrics or technique changes.
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Extra info for Cleaning Printed Wiring Assemblies in Today’s Environment
Tuck, 1. Op. cit. p. 40. 20. Navy Electronic Manufacturing Productivity Facility, Ridgecrest, CA, Fall 1989. 21. Elliott, D. , and 1. GHeta. Op. , p. 6. 22. Muir, 1. My First Summer in the Sierra, Chapter 6, p. , 1916. 1. 1. INTRODUCTION Purpose and Chapter Description To select cleaning materials, processes, and equipment without understanding the basic nature of the residues one wishes to remove is imprudent. In fact, the cleaning strategy is best chosen by taking into account the activity and the composition of the soldering flux used.
Be- FLUX CONSIDERATIONS WITH EMPHASIS ON LOW SOLIDS 35 Fig. 7. Results of corrosion test. (a) Passing (b) Failing cause a concentrated flux material is used, the test is certainly a worst case condition. , electrolytic). Also, it creates an accentuated cooperlsolderlflux interface. Lastly, the interpretation of results is difficult, subjective, and qualitative only. An evaluation of "how green is green" and the extent of green or blue-green coloration is difficult to quantify. As with the copper mirror test, there is no middle ground between pass and fail.
GHeta. "In-Line High Pressure Solvent Cleaning of Surface Mounted Assemblies-Part IT," Technical Program Proceeding, NEPCON West, Anaheim, CA, February 1987, pp. 7. 14. Lennond, D. S. Op. , P 22. 15. Beer, F. "Cleanliness Testing of SM Assemblies," Printed Circuit Assembly, October 1989, pp. 48-51. 16. Kenyon, W. G. "New Ways to Select and Use Defluxing Solvents," Technical Program Proceedings NEPCON West, Anaheim, CA, February 1979. 17. Brous, 1. and A. F. Schneider, "Cleaning Surface-Mounted Assemblies with Azeotropic Solvent Mixtures," Electri-onics, April 1984, p.