Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

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step stencil

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step stencil | 26 January, 2021

We will be exploring the exciting world of step stencils for the first time and I am looking for any advice from anyone using regularly. This direction is because we have large caps and soldered standoffs along with medium pitch LGA's and QFP's on same side of PCB. The caps and standoffs have not survived well during some preliminary "drop" tests(solder points fractured and components detached)of final product. Visually the amount of solder at these components, although meeting IPC 610 class II is less than desired. Going to a thicker stencil will cause shorts on LGA's and QFPs. Any help is appreciated.

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step stencil | 27 January, 2021

IPC-7525 does a good job of giving guidelines for designing stencils, including stepped stencils

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step stencil | 28 January, 2021

Nowadays is not a big deal to cut step stencils. Stencil houses charge you around 100USD per step in addition to your regular price. Some places are welding the step area with a very small clearance and I have to say mostly it is pretty accurate. In your case it sounds like you should keep your stencil same as before and step up you big/heavy parts with another 2-3 mils.

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step stencil | 2 February, 2021

The main feature of the step on the stencil is the excess of paste on adjacent components. Clearance between step and fine pitch components must be at least 10 mm. Might better try over printing?

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step stencil | 2 February, 2021

Hello Charliem, Contact Steve Yen ( )at USA STENICLS INC. He'll give you better idea overprint or step . He has solid experience in design smt stencil. We've been receiving very good stencil from Steve.

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step stencil | 5 February, 2021

For components with the large pads, you can also use secondary soldering dispensing. Some printers like DEK have an option to mount a syringe with an auger valve to do dispensing after the printing step process. Obviously will not work if you have too many companies where you need to apply a high amount of solder paste.

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