I have a design with 1mm & .8mm pitch BGAs on it.

Using 0402 caps on back.

Question, does anyone have any input with problems etc using

0402 patterns created using the smallest pattern calculated with current calculator?

If I use smallest pattern 0402 it calculates out to about .56mm sq pads on .84mm centers.

The 1mm BGA works reasonably well with this size 0402 and with gaps in balls on the .8mm part that smallest pattern could work well too.

Any feedback will help.

We really can’t switch to 0201s on this project at this time.

Thanks

Bob

Bob,

You’re on the right track. Use the “Least” environment for EIA 0402 (1005 metric) chip components. No one should ever use the Most environment for this chip size due to excessive solder.

If you normally use the “Most” environment for library construction, use the “Nominal” environment for the 0402 (1005) land pattern.

If you normally use the “Nominal” environment for library construction, use the “Least” environment for the 0402 (1005) land pattern.

Too much solder on this micro-miniature 2-pin component causes tombstoning in the assembly reflow oven (especially when using lead-free solder).

Here are my recommendations for the largest 0402 (1005) chip capacitor land pattern and it's in the IPC-7351 Nominal environment. I also rounded the corners to reduce the paste mask volume and I would also thin the paste mask stencil to reduce the paste mask volume. However, you can use the "Least" environment dimensions with good results.

One other important rule that you should consider when using Footprint (Land Pattern) calculators for all chip component sizes less than 2 mm (80 mils). When inserting the "Terminal" min/max dimensions, enter the "nominal" terminal dimension in both min/max fields (no tolerance). The component manufacturer's often provide unrealistic tolerances and if you use them for these micro-miniature 2-pin components the resulting pad (land) size is too large.

 Hello Tom,
           Can you explain little more detail on 0402 land pattern calculation.

   1.In what all packages we should provide "Terminal " Dimesions as nominal instead of min and max.

     (ex:0201,0402,0603,0805 packages)

   2.Can you be more specific to what is unrealistic tolerances ?

     
     Case 1:    
  
     http://capacitoredge.kemet.com/capedge2/intellispec.jsp?pn=C0402C104K4RACTU&displayPN=C0402C104K4RACTU" rel="nofollow - http://capacitoredge.kemet.com/capedge2/intellispec.jsp?pn=C0402C104K4RACTU&displayPN=C0402C104K4RACTU

        In the above attached datasheet link the terminal dimesion is 0.3 +/- 0.1 mm.

         What would be T min and T max ?

      
    Case 2:

           http://www.mouser.com/ds/2/40/cx7r-218113.pdf" rel="nofollow - http://www.mouser.com/ds/2/40/cx7r-218113.pdf

           In this datasheet the terminal size 0.25 +/- 0.15 mm .

           What would be T min and T max ?

We had a meeting with IPC-7351 committee last week and we adjusted the "TOE" solder joint goal for parts less than 1.6 mm length. So I have to delete the comment about using only Nominal dimensions for the component terminal because we fixed that in the IPC Calculator in the V2014.11 release.

Here is the new solder joint goal chart for chip components. These new values for miniature parts will eliminate tombstoning issues and provide the best paste volume for the assembly process.

I highly recommend that you download this new paper on Surface Mount Components -

http://www.pcblibraries.com/forum/surface-mount-component-families_topic1391.html" rel="nofollow - http://www.pcblibraries.com/forum/surface-mount-component-families_topic1391.html

This paper provides the latest component families and terminal types and their related solder joint goal tables.

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" -

Hi,

This is my 1st post after joining few days ago.

Your pad size is the Least Environment. This is good for Nominal.