0402 Min Size Land Pattern

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   Great, thank you very much. I see the formula used so it can be more precised i believe.

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DenisFr Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 08 Nov 2016 Status: Offline Points: 7	Post Options Post Reply Quote DenisFr Report Post Thanks(0) Quote Reply Topic: 0402 Min Size Land Pattern Posted: 09 Nov 2016 at 1:20am
	Great, thank you very much. I see the formula used so it can be more precised i believe.



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: 6031	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 08 Nov 2016 at 7:49am
	You should download the Surface Mount Reference Calculator and it will allow you to change all the values so you can see how the IPC mathematical model works. www.pcblibraries.com/downloads If you're using V2016.14 it's in this folder - C:\Program Files (x86)\PCB Libraries\Library Expert 2016\Documents The IPC math considers the Component Package and Terminal Lead Tolerance and adds a Fabrication and Assembly Tolerance plus a Toe, Heel and Side solder joint goal.
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DenisFr Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 08 Nov 2016 Status: Offline Points: 7	Post Options Post Reply Quote DenisFr Report Post Thanks(1) Quote Reply Posted: 08 Nov 2016 at 3:58am
	Hi Tom, I try to understand how the footprints are calculated with Library expert. Especialy "S". In IPC, i saw that Sm=Lm-2xTM, but i don't find the same result than in the calculation tab. For example, for a 0805 resistor, i will have Sm=1.85+2x0.65=0.55 while i obtain 0.816 in library expert. Did i miss a parameter ? Thank you very much Denis

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: 6031	Post Options Post Reply Quote Tom H Report Post Thanks(1) Quote Reply Posted: 21 Apr 2015 at 5:48am
	I don't think you understand Library Expert. The initial settings are IPC-7351 compliant but the user has several options. 1. You can select the Footprint tab and enter the mfr. recommended pattern dimensions. 2. You can open the "Terminal Settings > Density Level" and change the Toe, Heel and Side solder joint goals. 3. Or, what some users are starting to do is in the Terminal tab is change the Placement and Fabrication Tolerances to 0 (zero) due to the accuracy of the machines and processes in 2015. I would not take the IPC-7351 default settings as the holy gospel as the "Standard" was recently downgraded to a "Guideline". And new updated solder joint goals are currently in testing. So maybe the mfr. recommendation is the way to go. Then you can blame any problems on the mfr.
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jayx Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 29 Mar 2015 Status: Offline Points: 7	Post Options Post Reply Quote jayx Report Post Thanks(1) Quote Reply Posted: 20 Apr 2015 at 3:54pm
	Hi Tom, OK, as advised I've downloaded Library Expert Lite and entered 1005 (EIA 0402) dimensions (based on Kemet: D=1±0.05, E=0.5±0.05, A=0.5±0.05. L/L1=0.3±0.1mm) and land pattern results are: L/L1=0.59, W=0.6, S=0.22mm. Very similar to your recommendations apart from S which is two times smaller (it's 0.5mm in your recommendation). It's quite big difference for such a small component, and in fact Kemet recommends S=0.28mm so close to the above calculations. Reducing tolerance or change density level don't get me close to your recommended S dimension, could you comment please?

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: 6031	Post Options Post Reply Quote Tom H Report Post Thanks(1) Quote Reply Posted: 29 Mar 2015 at 2:32pm
	The Free Library Expert Lite provides all the Land Pattern dimensional data for 144 different component families - www.pcblibraries.com/downloads You can also switch between IPC-7351 Density Levels. Since the V2015.09 Library Expert Lite has all the latest IPC-7351C mathematical formulas for packages less than 0603, you'll be able to see distinct differences between 0603, 0402 and 0201 chip components. It also has all the rules for Molded Body Tantalum Capacitors and Diodes. The Free Library Expert Viewer can load FPX files and if you purchase the IPC-7351B you get a special Viewer that comes with 5,000 different component package dimensions. http://landpatterns.ipc.org/default.asp
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jayx Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 29 Mar 2015 Status: Offline Points: 7	Post Options Post Reply Quote jayx Report Post Thanks(0) Quote Reply Posted: 29 Mar 2015 at 2:19pm
	Hello, I was trying to find recommended land pattern design for the most popular packages like 0603, 0805, SO8 etc. but it turns out to be pretty difficult. I found IPC-7351 and its 3-Tier approach but don’t really understand how can I calculate correct pad sizes using these values. Also I've seen PCB Library Expert SMD Reference Calculator but it returns incorrect values - try to enter 1608 (EIA 0603) package dimensions L=1.6, T=0.35, W=0.3 with ±0.15mm tolerance as found in Kemet datasheet http://www.kemet.com/Lists/ProductCatalog/Attachments/351/KEM_CC103_AUTO_SMD.pdf and calculated pads will overlap. Finally I've found information that ModelSource libraries available to download for DesignSpark are created to the IPC-7351 standard. However supposedly also based on IPC-7351 Kemet land pattern design recommendations in document mentioned above (page 12) is slightly different than these in ModelSource. By the way Kemet recommendations are also slightly different for 1005 (EIA 0402) than these in this topic. I know the differences are not big and in real life probably doesn’t matter but would be nice to keep land patterns the same across the industry. So I'm really surprised there are no exact dimensions specified e.g. in IPC-7351 for the most popular packages.

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: 6031	Post Options Post Reply Quote Tom H Report Post Thanks(1) Quote Reply Posted: 11 Feb 2015 at 3:06pm
	Your pad size is the Least Environment. This is good for Nominal.
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SandroLanot Members Profile Send Private Message Find Members Posts Add to Buddy List New User Joined: 11 Feb 2015 Status: Offline Points: 13	Post Options Post Reply Quote SandroLanot Report Post Thanks(0) Quote Reply Posted: 11 Feb 2015 at 2:55pm
	Hi, This is my 1st post after joining few days ago. Is there any assembly attachment issues if my 0402 land pattern is 0.40 mm x 0.50 mm, with 1.00 mm pitch?

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: 6031	Post Options Post Reply Quote Tom H Report Post Thanks(0) Quote Reply Posted: 06 Feb 2015 at 7:24am
	The 1608 is the smallest chip that has 3-Tier Environment Density Levels Least, Nominal and Most). It depends on which version of Library Expert you are using (Pro or Lite) as to where you change the Environment. If you are using Library Expert Lite you change the Environment in the "Terminal > Environment" tab. If you are using Library Expert Pro you change the Environment in "Setup Preferences > User Preferences > Design > Surface Mount Environment > Drop Down" -
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