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How To Make Hybrid QFN with Multiple Thermal Pads?

Printed From: PCB Libraries Forum
Category: PCB Footprint Expert
Forum Name: Questions & Answers
Forum Description: issues and technical support
URL: https://www.PCBLibraries.com/forum/forum_posts.asp?TID=1947
Printed Date: 18 Nov 2024 at 10:35pm


Topic: How To Make Hybrid QFN with Multiple Thermal Pads?
Posted By: Matthew Lamkin
Subject: How To Make Hybrid QFN with Multiple Thermal Pads?
Date Posted: 18 Aug 2016 at 2:10am
Hello, can you please advise how to make a QFN that has 3 EP pads in the middle instead of just one?

The attached PDF shows how it should be.
uploads/830/21-0177.PDF" rel="nofollow - uploads/830/21-0177.PDF

Its basically an existing footprint that needs to be taken into the footprint designer and the middle pad changed, moved and 2 more added.

However I cannot see how to open a footprint from the existing list in the surface mount families (or an FPX file) and take that through to the FP designer for editing?

Also what would I name it?

EDIT: Not to worry - I have named it MAXIM_21-0177

Cheers,
Matthew


Replies:
Posted By: Tom H
Date Posted: 18 Aug 2016 at 5:47am
I would start building the QFN with the QFN with no Thermal Tab Calculator. I would use the Nominal Density Level and Oblong pad shape to insure a good clearance for the corner pads.

Then I would select the toolbar icon "Move Footprint To FP Designer".

Then I would select the Pad Stack icon and select New button and create the 3 Thermal Pads in the pad stack designer using a 50% paste mask reduction checker board pattern.

Then in the Pins Tab select each Thermal Pad Stack and enter the coordinate to place them.

Then I would add Legend and Assembly polarity marking.

Select the Finish Tab and enter the Component Family, Mfr. Name, Case Code 21-0177 and Mfr. Part Number and last select the OK button and Add to Lib icon.

The entire process should take about 5 minutes, but I would figure out the X/Y coordinates for each Thermal Tab center before even starting to have them handy when I place them.

If it takes longer than 15 minutes, then you should order the part via POD Part Request and have PCB Libraries build it and email you the FPX file.
 


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Posted By: Matthew Lamkin
Date Posted: 18 Aug 2016 at 5:54am
AHA... an RTFM and look at what the icons are moment :)

I actually built the QFN in the LEP and finished it off in CADSTAR for the inner pads.

Cheers Tom

Posted By: Matthew Lamkin
Date Posted: 19 Aug 2016 at 3:28am
And now if I have done the above - entered all the details about a component then thought "I'll just add a couple of extra pads" and taken it into the Designer.

Then I realize I need to change a dimension etc that I possibly entered wrong.

There seem to be no return, no ability to modify all those previous min\max settings dimensions and settings etc.

Can you point me to the magic button now?

Oh yes, and if your in the FP and happen to click on Surface Mount, how to get back to the designers tabs? hitting the designer wipes the sheet out to start again???

Posted By: Tom H
Date Posted: 19 Aug 2016 at 6:59am
It's a one way street. The Calculator cannot handle FP Designer features.

Get the Calculator part done correctly and save it to FPX.

Then move it to FP Designer.

If you need to make a change reopen the FPX and recreate the FP Designer.

Save your work.



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Posted By: Tom H
Date Posted: 19 Aug 2016 at 7:11am
I forgot to mention that we updated the Calculator the FP Designer code yesterday and uploaded a new V2016.10 pre8.

We intend to officially release .10 next week and then release V2017 in October.



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