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What is the Life Span of a Profile Board?



What is the Life Span of a Profile Board?
What is the life span of a profile board? How many times can I use one test board to profile a reflow oven before throwing it away and why? The Assembly Brothers, Phil Zarrow and Jim Hall, answer these questions.
Board Talk

Transcript


Phil
And welcome to Board Talk, this is Phil Zarrow and Jim Hall, the Assembly Brothers, Pick and Place coming to you from Board Talk headquarters from high above Mount Rialto.

Jim
The question today comes from PV.
What is the life span of a profile board? How many times can I use one test board to profile our reflow oven before throwing it away and why?

Phil
Now, you talking about a normal person or me? I had this one board, it was an old ugly looking -- it originally was some Alcatel board and originally we were using it, we were at Vitronics, and it was properly -- thermocouples were properly applied, thanks to Al Cabral at the time, using conductive epoxy and that board has seen -- because we use to use it benchmark all kinds of things.

It had seen over a hundred thermal reflow profiles. Some extreme, because we were testing ovens on the old radiant machines and stuff like that, the board itself, well you know it's still there, all the thermocouples were intact.

On the other hand, most of the components were gone, parts of the board were charred, crumbling into dust. So the answer to your question is long before it turns to dust, the reality is that if it's going to be ongoing program that you are going to want to profile, audit the profile from time to time, there are tools for doing that.

Jim
Most of the people who manufacture, profile data loggers, also will supply you with what they call a calibration vehicle which is a large board-shaped piece of usually delmat, high temperature material with some variety of thermocouples attached to it, suspended from it, giving you a high mass, low mass and so forth. These are used for a calibration; it's a very durable piece of hardware, very repeatable. And you can get a new one that is calibrated.

So, in the ideal, or the theoretical, or the best case world what is the best practice we like, we'd like to talk about that. You sacrifice a real assembly to the profile gods. You take a fully loaded board with all the components on it, attach thermocouples to the key locations using light gauge thermocouples with tiny amounts of either high temperature solder or high temperature epoxy, so that you don't add too much thermal mass to what you are trying to measure.

Phil
And that is very important, adding too much mass would really throw off your readings.

Jim
And then you use it to develop your profile and hopefully you do that, you are using predictors, and so forth, it doesn't take you too many runs, maybe it's gone through two or three or four runs, that is certainly safe. Then you have that recipe established in the oven, then you run your calibration vehicle through the oven using the same recipe.

Now you can use your calibration for set up confirmation whenever you run that board again, you reenter that profile in the oven, want to confirm that you are getting the same thermal processing, you run your calibration. You now have a calibration profile which may not be the same temperatures as you got in the board, but it's directly correlated to it up front.

So then you keep that golden actual profile board carefully stored in a closet so it doesn't get destroyed. So if you really have a critical issue, maybe you have some defects, you want to change the recipe to create a slightly different profile board. You can then pull that out, but you don't use it over and over again daily or weekly or whatever your calibration -- validation protocol is and you don't get like Phil's board where components have fallen off and it's so charred and burned and there's been so much juice cooked out it.

Yes, but the bottom line is you question whether it is responding thermally to the oven in the same way that the original board when it was virgin.

Phil
So there is a solution in hand and that's our free advice today, money back guarantee on that, and you have been listening to Board Talk with Jim and Phil, the assembly brothers. And whatever you are doing, however you profile that oven, whatever you do --

Jim
Don't solder like my brother.

Phil
And don't solder like my brother.



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