After much testing, BEST has chosen to upgrade its standard SMT stencil material to Tension™ material from Datum™. This material, after 2 plus years in the making has proven to give the kind of printing performance of nanocoated stencils without the downsides of these stencils. A recent study has also indicated that the consistency of the printing performance is even better than nanocoated stencils. This same study, which compared the printing of fine grain stainless, nanocoated fine grain stainless to this new ultra fine grain stainless pointed out that this Tension™ was truly the best giving the most consistent highest paste release volume results. While this 5-8% better volume performance boost may not be warranted on older technology boards, todays’ fine pitch rich boards demand whatever is required to get the yields up. Why would you not use this type of material to improve your process yields.
Cut quality showing smooth walls of ultra fine grain Tension™ aperture at 400X
The downsides of the nanocoating process for improved stencil performance are well-documented. The transfer efficiency of these coated stencils is higher with improvements over the other standard materials of from 3-10%. The downsides of the nanocaoted stencils are also well-documented. First the nanocoated stencils take time to process. This means the nanocoated stencils cannot be delivered in as quick of a time frame. Secondly the nanocoated stencils are wiped off after a period of tie which means that that they need to be recoated. Lastly, extra $20-40 per stencil cost is something that the user needs to bear.
Solder Paste Volume comparison from APEX 2017 Presentation Showing 10% Better Paste Release from Tension™ Material
BEST has now adopted this Tension™ material as its standard material for 4 and 5 mil thick stencils. The cost of this material has forced us to slightly increase our end selling prices by a few dollars. Just a few additional reworks or touchups will more than pay for itself in terms pf rework. We urge you to give it a try.