What is Surface Mount, Wettable Flank?


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Recently many of the product categories on the Digi-Key site have added a new mounting type of Surface Mount, Wettable Flank. While this is not a brand new mounting type, with recent growth in use and requests it is the first we have calling it out as a different mounting option.

So what is a wettable flank? A wettable flank is calling out a specific design in which the mounting edge of an IC has a fillet that allows you to see and test that a proper connection has been made on a pad that is for the most part not visible once soldered on a board. This aids in inspecting packages such as QFNs with AOI (Automated Optical Inspection).

In a recent training with Allegro Micro systems I was informed that the drive for Wettable flank came from the Automotive industries, however is growing and they are starting to see uses in other areas. As such you will see additional products in the future with this option.

Let’s take a look at the parts. First part SN65HVD75DRBR. This would be a standard 8-VDFN package.
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Now take a quick look at the part TCAN1042GVDRBTQ1 this part has the wettable flank option. Looking closely at the picture you can see the grove in the mating edge of the part.

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This diagram from Allegro Micro Systemspackaging publications helps show how a solid fillet has been formed with the board and thanks to the design is optically inspectable.

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In the Blog pictures below TI shared AOI pictures and incite behind why you want to use wettable flank. You can see with the increased area how the inspection and testing is much easier that the standard packaging.
Make automatic optical inspection easy thanks to packages with wettable flanks

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