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Double-sided reflow with a Altera 240-pin RQFP

Steve Gregory

#25009

Double-sided reflow with a Altera 240-pin RQFP | 30 June, 2003

Has anybody ever done a double-sided reflow with a Altera 240-pin RQFP on the bottom? The part has a heatsink in the top and weighs just over a half-ounce...

Thanks in advance!

-Steve Gregory-

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RDR

#25011

Double-sided reflow with a Altera 240-pin RQFP | 30 June, 2003

Try searching the archives, I saw the formula posted in an earlier thread I belive that relating to Double sided with BGAs but I am not sure I think Dave F. posted this one. So what is an "R"QFP I haven't heard of that one before.

Russ

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Steve Gregory

#25012

Double-sided reflow with a Altera 240-pin RQFP | 30 June, 2003

Hi Russ!

An "R" QFP is what Altera calls their Plastic Quad Flatpacks that have a heatsink in the top...they actually call them Power Quad Flatpacks.

I'm familiar with the formula, of how one can figure out if there's enough surface tension for a part to stay on the bottom. But this part's mechanical drawing shows a toe down configuration for the foot, and with the heatsink, it weighs over a half-ounce. I'm just a little leery that it will fall off during the second side reflow...I've 5 of these beauties on each side of the board.

I was thinking of putting a dot of loctite chipbonder in each corner...unless I heard from somebody that it's not necessary.

-Steve Gregory-

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#25016

Double-sided reflow with a Altera 240-pin RQFP | 30 June, 2003

Hi Steve

We don�t double reflow this part. We wouldn�t consider it without a fixture or some other support.

You know that sound, the almost involuntary sound that patrons in a restaurant make when a waiter drops a glass or a tray? It�s kind of an �oooooo� sound. Well if you run these parts, the sound that the troops at your plant will make will be so loud as those pups start Peter Panning to the floor that the people in the front will stop playing games on the computer and walk out back to find-out what�s going on.

Do the numbers: * Part weight: 15.1 gm * Lead toe to heel: 0.46/0.66 mm * Lead width: 0.17/0.27 mm

Lead wetting area = 240* [0.46*0.17] mm^2 = 18.7 mm^2 [0.03inch^2] Weight of component to total pad mating area ratio: 15.1 gm / 18.7 mm^2 = 804.6 mgm per mm^2 [519.1 gm per inch^2]

A commonly acceptable ratio is: 50 mgm per mm^2 [30 gm per inch^2] Pushing the boundary ratio is: 44 gm per inch^2

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