smt
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smt [2016/01/28 18:05] (current) |
| ====== Stencil notes ====== |
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| 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. |
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| To calculate the optimal stencil thickness for fine pitch placement, IPC standard #7525 states: |
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| > Stencil Thickness = 2.64 + 0.0831 * Pitch of component (in mils) |
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| 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: |
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| > 0.65 mm / 25.4 = 0.0256 inches = 25.6 mils |
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| Then calculate according to the equation above |
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| > 2.64 + 0.0831 * 25.6 = 2.13 + 2.64 = 4.77 mil |
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| So for SSOP parts, 4 to 5 mil is the thickest you should go |
/home/ladyada/public_html/wiki/data/pages/smt.txt · Last modified: 2016/01/28 18:05 (external edit)