Michael L. Martel
Speedline Technologies Inc.
Franklin, Massachusetts, USA
Summary
Fine pitch/fine feature solder paste printing in PCB assembly has become increasingly difficult as board geometries have become ever more compact. The printing process itself, traditionally the source of 70% of all assembly defects, finds its process window narrowing. The technology of metal blade squeegees, with the aid of new materials, understanding, and settings such as blade angle, has kept pace with all but the smallest applications, e.g., 200μ - .50 AR and 150μ - .375 AR, which have been pushing blade printing technology to its limits.
Enclosed media print head technology has existed, and has been under increasing development, as an alternative to metal squeegee blade printing. Until recently, the performance of enclosed print heads had been comparable to the very best metal squeegees, but advances in enclosed print media technology have now made it a superior alternative to squeegee blades in virtually all applications.
Conclusions
Enclosed media printing technology is a suitable replacement for metal squeegee blades particularly for demanding fine pitch applications and mixed low and high volume paste consumption applications. The ability of enclosed media printing to successfully meet the volume fill requirements of ever-shrinking aperture sizes and lopsided aspect ratios is sufficient justification. Additionally, the paste savings over squeegee blade printing are significant, so much so that in the current economic climate, these cumulative savings can contribute to a relatively quick payback on the equipment investment, and have a measurable effect on the "bottom line."
Initially Published in the IPC Proceedings
Comments
Readers should bear in mind that this technology is not an "alternative to metal squeegees", it is simply an "alternative" - the reason: "Enclosed Media Printing" relies on metal squeegees most directly, These print heads contains two metal blades and we are the supplier of these blades to the makers of Enclosed Head Printing Systems. Users should also note that with regard to these metal blades, they are usually thinner, they both stay in contact with the stencil each print print cycle so for the most part, they are a key part of the process. Thank you for the opportunity to chime in. With regard to the assertions about print quality - I concur that the Enclosed Head printing method may have some technical advantages for very fine aperture printing due to the high-squeegee angle of attack reverse shearing that happens with this method. Cheers!
