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The Knowledge and Know-how Connection
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May 24, 2013
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Recommended Lead to Hole Ratio
What is the proper minimum gap between a round conductor lead and a PCB hole that will allow for a proper solder fill?
Expert Panel contributors for this topic:
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Leo Lambert, Vice President, Technical Director, EPTAC Corporation | |
Bill Coleman, Vice President Technology, Photo Stencil | |
Rodney Miller, Capital Equipment Operations Manager, Specialty Coating Systems | |
Mitch DeCaire, Sales Manager (Americas), Cogiscan, Inc. |
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Views: 5508
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I would not change the hole to lead size ratio for thicker boards. The basic component plated through hole size was selected for ease of inserting through hole components and the basic hole size was 0.038" finish hole size and on 0.060" board this was approx 2:1 aspect ratio and 3:1 for 0.091" boards with the aspect ratio being hole size versus board thickness. Keeping in mind the accuracy of the insertion equipment and such, these were the hole sizes we used at Digital Equipment during my time there as we wanted the plated through hole to be about .006" to .015" larger than the component lead. This allowed the solder to flow up into the plated through holes, through capillary action and the hydrostatic pressure of the wave solder system. Since then the industry has miniaturized the boards and holes and we now have holes which are drilled with 0.006" drills which is a 10:1 aspect ratio but with no components. The component holes are still about .038" and solder fill is still being met according to the industrial specifications.
Hope this helps.
Leo Lambert
Vice President/Technical Director
EPTAC Corp
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Would the lead to hole ratio change with boards thickness greater than .062, such as .093 or .125?
Donald P Mazzi, Hewlett Packard