Pad trimming for

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   Hi,

We've just stared using PCB Libraries as a reference to generate our footprints. We are using JEDEC standards to reference component outlines.

Does anyone know why PCB Libraries does not trim the heel section for a pad when A1 (min)=0.00 mm, i.e.: the component body is sitting flush against the PCB? 

I'm concerned the Solder Paste on the Heel goal of the pad will slightly lift the component during Surface Mount reflow.

For example: I'm using JEDEC MO-193 AB to draw a SOT23-5 footprint. The heel part of the pad is not trimmed.

Thanks

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ivanbajic Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 06 Jan 2020 Status: Offline Points: 3	Post Options Post Reply Quote ivanbajic Report Post Thanks(0) Quote Reply Topic: Pad trimming for Posted: 15 Jul 2020 at 7:56pm
	Hi, We've just stared using PCB Libraries as a reference to generate our footprints. We are using JEDEC standards to reference component outlines. Does anyone know why PCB Libraries does not trim the heel section for a pad when A1 (min)=0.00 mm, i.e.: the component body is sitting flush against the PCB? I'm concerned the Solder Paste on the Heel goal of the pad will slightly lift the component during Surface Mount reflow. For example: I'm using JEDEC MO-193 AB to draw a SOT23-5 footprint. The heel part of the pad is not trimmed. Thanks



Tom H Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 5716	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 15 Jul 2020 at 8:22pm
	In Preferences > Rules > Minimum Trim Standoff, if you set the value to 0.05 the calculator will automatically trim the pad from under the low profile package when the A1 dimension is less than 0.05.
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ivanbajic Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 06 Jan 2020 Status: Offline Points: 3	Post Options Post Reply Quote ivanbajic Report Post Thanks(0) Quote Reply Posted: 15 Jul 2020 at 9:08pm
	Thanks Tom I had it set to 0.00, so I had about 0.215 mm from the body outline to be end of the pad. Setting the "Min Trim Standoff Height" to 0.05 mm does trim the pads to 0.05 mm.

Tom H Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 5716	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 16 Jul 2020 at 8:02am
	The New V2020 Footprint Expert will default the Minimum Trim Standoff Height (A1) 0.03 mm. But the user can change it to whatever they want. The V2020 Beta can be downloaded at www.pcblibraries.com/downloads
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