Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

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double side soldering

Jean Michel


double side soldering | 4 September, 2001

During the solderin of a double side board, how can I calculate the maximum weight of a component I can put in the first side to avoid the component fall down in the oven (depending on the soler join surface) ?

Are there some rules ?

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double side soldering | 4 September, 2001

Assuming you're asking about double sided reflow soldering ...

Use pad mating to lead wetting area.

Bob Willis has found the ratio to be as much as 44 grams/sq in. Check Bob's site [Electronic Presentation Sevices] for more.

Phil Zarro uses the more tradional 30 gm per sq inch (50 mgm per mm2). Check Phil's site [ITM Inc] for more.

Check the fine SMTnet Archives. This is not a new topic here.

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double side soldering | 7 September, 2001


A lot depends on your process. can you add a dot of adhesive after screen printing and before placement? This works well for larger heavier parts. A second suggeestion is to reprofile your board. Try keeping the bottom side cooler. I do this a lot and it works great.

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double side soldering | 10 September, 2001


Thanks for your quick answer, I read some paper on the forum.

I would like to learn more and to know how to obtain the result of x gr / sq in (mathematic methode). Do you know where can I found it ?


J Michel

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double side soldering | 11 September, 2001

Like most things in electronic assembly, this is not astrophysics.

People have pasted boards, placed components, turned the board up-side down, run the board through a reflow oven, and generalized about which components: * Fall off the board. * Don't fall off the board.

... by calculating a weight of component to total pad mating area ratio. [What could be more simple and to the point than that?]

Two people that have written articles about this work are: * Phil Zarro [Circuits Assembly, Sept 1996, p36-41] * Bob Willis.

The rule of thumb they have developed is stated above. Check their sites.

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