Differences

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--- smt [2016/01/28 18:05]
+++ smt [2016/01/28 18:05] (current)
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+====== Stencil notes ======
+Stencil thickness makes a difference! Thicker stencils allow more paste to be deposited which is good for large parts and connectors but can cause shorts with finer pitch parts.
+To calculate the optimal stencil thickness for fine pitch placement, IPC standard #7525 states:
+> Stencil Thickness = 2.64 + 0.0831 * Pitch of component (in mils)
+So, say for an FT232RL chip, which is a SSOP part with 0.65mm pitch. First figure out the pitch in thousands of an inch:
+> 0.65 mm / 25.4 = 0.0256 inches = 25.6 mils
+Then calculate according to the equation above
+> 2.64 + 0.0831 * 25.6 = 2.13 + 2.64 = 4.77 mil
+So for SSOP parts, 4 to 5 mil is the thickest you should go

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