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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Cooling

Ng

#12818

Cooling | 24 January, 1999

It has been known that sufficient cooling after soldering is important in order to get a stronger joint during its solidification stage. And it has been so much emphasised with reflow oven. But, why many models of wave soldering machine do not come with cooling features at the pot exit area. It is only an optional item even for some high-end wave soldering machine. Can somebody help. Thanks

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Steve Gregory

#12819

Re: Cooling | 24 January, 1999

| It has been known that sufficient cooling after soldering is important in order to get a stronger joint during its solidification stage. And it has been so much emphasised with reflow oven. But, why many models of wave soldering machine do not come with cooling features at the pot exit area. It is only an optional item even for some high-end wave soldering machine. Can somebody help. Thanks

Hi Ng!

I'm pretty sure it has something to do with the overall process temperatures between the two. During wave solder, boards will never see the kind of temperatures for the period of time that a board sees during reflow, so normally there isn't the latent heat in a wave soldered board that a board coming out of the spike zone of a reflow oven has. There are exceptions to that I know, I've seen some boards that have a lot of copper and component mass that are pretty toasty for a while after exiting the wave.

One aspect to the wave solder cooling question is that you want the board to stay pretty warm immediately after passing across the wave, otherwise you'd have a bunch of icicles or flags to contend with. One other thing that I can possibly think of as to why cooling is not as important after wave as it is with reflow, is the differences in the solder joint geometry and surface area where the metalurgical bond is taking place between the two technologies.

You're right that a quickly cooled solder joint will form a smaller, tighter grain structure, but with PTH solder joints if that doesn't happen, so what? A PTH joint is so big and beefy in comparison to a SMT joint, that large grain structures probably aren't a concern at all.

Good question! Got me thinkin' a little today instead of veggin' out!

-Steve Gregory-

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Ng

#12820

Re: Cooling | 25 January, 1999

| | It has been known that sufficient cooling after soldering is important in order to get a stronger joint during its solidification stage. And it has been so much emphasised with reflow oven. But, why many models of wave soldering machine do not come with cooling features at the pot exit area. It is only an optional item even for some high-end wave soldering machine. Can somebody help. Thanks | | Hi Ng! |

Hi Steve,

Thank you for your ideas. What I meant was actually for those board with SMT components on the soldering side, not so much for the THT components. It would not be possible to put the cooling too near to the wave exit as it will definitely causing thermal shock, however, do you think cooling fan located at about 8 inches away from the wave exit.

Thank you again | I'm pretty sure it has something to do with the overall process temperatures between the two. During wave solder, boards will never see the kind of temperatures for the period of time that a board sees during reflow, so normally there isn't the latent heat in a wave soldered board that a board coming out of the spike zone of a reflow oven has. There are exceptions to that I know, I've seen some boards that have a lot of copper and component mass that are pretty toasty for a while after exiting the wave. | | One aspect to the wave solder cooling question is that you want the board to stay pretty warm immediately after passing across the wave, otherwise you'd have a bunch of icicles or flags to contend with. One other thing that I can possibly think of as to why cooling is not as important after wave as it is with reflow, is the differences in the solder joint geometry and surface area where the metalurgical bond is taking place between the two technologies. | | You're right that a quickly cooled solder joint will form a smaller, tighter grain structure, but with PTH solder joints if that doesn't happen, so what? A PTH joint is so big and beefy in comparison to a SMT joint, that large grain structures probably aren't a concern at all. | | Good question! Got me thinkin' a little today instead of veggin' out! | | -Steve Gregory- | |

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