Gluing Quality Issue !!!

There may be supplier guidelines or accepted practice, but there is no shear specification for printing either paste or glue.

Beyond the issue of not knowing the shear value, what's the problem that you see when printing glue?

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In a previous job, we had torque off requirements for different sized components for our screen print adhesive (non-conductive in our case). We used a torque watch that would measure max torque, so we could test production boards, shear testing was impractical. The values were determined before my time, but I think we worked with the adhesive manufacturer.

Like was said before, there is no spec on shear or torque strength, because there are too many variables to cover all circumstances (component metallization, board metallization, solder composition, etc.). Not much help I know, but torque off strength was a property that could be measured quickly and easily, just another option.

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Loco

[snip] "The print mode is another consideration. Printers are designed with a squeegee bar and a flood bar. In flood mode the flood bar spreads the paste, and in print mode the squeegee applies pressure, such that the actual printing takes place. When the flood bar is spreading the paste, the squeegee is up [riding] and when the squeegee is printing, the flood bar is up [riding]. Since the two bars are identical, if the design allows, their functions can alternate. Some equipment can perform only in the flood/print mode, and others offer both print/print and flood/print modes. Some of the older machines are not suitable for stencil application, because they are not flexible and cannot provide the print/print mode. Only the print/print mode can be used with stencils, because the holes are completely open and it is necessary to prevent the paste from oozing out of the holes and dripping onto the substrate surface. For screens, the flood/print mode is used. Naturally, equipment is more desirable if it can function in various modes and can be used for both stencils and screens." [Surface mount technology: principles and practice, RP Prasad, Springer, 2nd edition, 1997] [snip]

That aside, your issue probably has nothing to do with printing. Here's a link to one of the threads on the topic from the fine SMTnet Archives that's closer to the solution; http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=23422

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