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IPC-7351 SMD & PTH Reference Calculators |
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dfournier 
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Joined: 06 Jul 2018 Status: Offline Points: 2 |
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 Posted: 10 Jul 2018 at 5:24am |
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Hello Tom, Thank you for informations. Does IPC define Thermal ID and OD? I don't find explanation that define these diameters. I use CADSTAR software and Thermal ID and OD are differently defined.  |
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Tom H
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Joined: 05 Jan 2012 Location: San Diego, CA Status: Offline Points: 5941 |
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Posted: 09 Jul 2018 at 7:32am |
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Thermal Relief is for all PTH pins that connect to a Plane. A PTH lead with a direct connection to a GND or VCC Plane can have a cold solder joint because the plane can dissipate all the heat from that connection. OD = Outside Diameter of Plane Pad The thermal ID & OD are connected with Spokes from the pad to the copper plane.  |
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dfournier
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Posted: 09 Jul 2018 at 12:09am |
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Hello guys, I start to create footprints with IPC-7351. Could you tell me what are Thermal ID and Thermal OD for PTH?
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Tom H
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Posted: 26 Jan 2018 at 2:55pm |
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IPC-7351 has no recommendation on using circular pad shape for Chip Components.
The best source for this recommendation would be the Assembly Shop source that you are currently using. |
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IainSynaptive
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Joined: 07 Jun 2016 Status: Offline Points: 1 |
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Posted: 26 Jan 2018 at 2:32pm |
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Good evening and Thank you for Everything you've created here!
I have simple a question regarding Chip components and Circular Pads: Are they acceptable? I've been unable to locate any published Pros/Cons to this method and PC-7351B doesn't offer any guidelines to this practice. Are you able to provide any insight? Thank you in advance, |
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Tom H
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Posted: 24 Oct 2017 at 3:11pm |
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The Rectangular End Cap Side Goals need to be addresses in 7351 because Resistors only have metal Terminals on 3 sides and do not (cannot) have a side fillet. But Chip Capacitors have metal Terminals on 5 sides and a side fillet is a reality.
IPC-7351 is no longer a Standard (even though the cover of IPC-7351B says so). IPC-7351 is now a "Guideline" and should be used as such. Land Pattern pad size and spacing are flexible and not rigid hard core values. The IPC-J-STD-001 Standard for solder joint goal acceptability is the ruling standard for Land Patterns and it has a higher priority over IPC-7351. PCB Libraries "Library Expert V2017" solder joint goals for Toe, Heel and Side values reflect IPC-J-STD-001 and not IPC-7351B. |
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KevinA
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Joined: 24 Oct 2017 Status: Offline Points: 2 |
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Posted: 24 Oct 2017 at 3:01pm |
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That made a differance (User data in the WHITE fields :)) but I still ended up with a .62 for pitch meaning .38 gap between the pads of a device who's overall length is .25, they don't have a diamensional tolerance until type 063. Toe=0.05 heel=-0.03 side=-0.03
The other thing I've noticed is the manufactures have smaller pads with no side compared to any version of IPC-7351, unless they are Kemet, Kemet uses IPC-7351 but no version shown. |
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Tom H
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Posted: 24 Oct 2017 at 12:36pm |
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You need to adjust the Toe & Heel values. The Chip component does not have a 0.35 mm Toe and Heel.
Download the PCB Libraries Solder Joint Goal tables here - |
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KevinA
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Posted: 24 Oct 2017 at 12:22pm |
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Downloaded the Calculator and tried it but I must be doing something wrong or my math is punked:
From TAIYO YUDEN:  I added B+A+B = L for Min and MAX  and ended with this:  Thanks |
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Nick B
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Posted: 20 Oct 2014 at 12:53pm |
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Please note the IPC-7351 Reference Calculator was just updated! There is now an Inserted Mount "IMD" (TH) Reference Calculator. Download it from this forum thread, or from www.PCBLibraries.com/downloads Nick |
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