Hi, I'm Brad Jolly and I'm an application engineer here at Keysight Technologies.
Today we're going to talk about how you set the minimum transmit power threshold for your
device when you're testing it with an X8711A functional IoT device tester.
So typically the way you start is this: you've got your curve for your known good devices
and you have your specification and so you'd simply set your minimum threshold right there.
You also probably want to move it in just a little bit to account for any uncertainty
in the measurement device.
Ideally then what you end up with is you've got your good devices here, your bad devices
have distribution looks like this and you're all set.
But what happens a lot of the time is you have some bad devices that still have decent
transmit power and it looks like this.
Now these may be devices that are functionally okay but they may have marginal defects in
them.
For example, they may have a billboarded resistor or something may be misaligned or you may
have a head-on-pillow sort of defect where you've got the solder down here and the device
is laying on top of it but you really don't have a good connection.
And so what you end up having to do is move this to the right, but when you do that, you
end up adding more cost and risk to yourself.
Or you can move this to the left, but if you do that, now you're shipping bad devices to
your customer and you don't want to do that.
So you've got a conundrum here so what do you do?
Well, what you do is you try to separate the two distributions as follows.
What you can do here is take this distribution and try to move it to the right so it looks
more like that.
How do you do that?
Well, that's a conversation you have to have with your suppliers and your process engineers
so that you end up with a more tightly distributed product for your good products.
Then what you try to do is move this to the left.
Well how do you do that?
Well, it turns out that that is not actually one homogeneous group of defects.
What you have is you have several defects, okay, of these different types and these different
colors represent different kinds of defects that make this up.
And what you do is you try to figure out what defects are causing the device to look like
a sort of a good device, but they're actually defective.
And so this case what we do is look at our Pareto of defects and go after the blue defects,
whatever that is.
So let's say that's a misaligned resistor or maybe that's a out of spec part of some
sort.
Then what we do is we implement some sort of upstream test there, perhaps pre-reflow
or post reflow automated optical inspection or AOI or maybe it's a reel change issue that's
causing the problems in which case it's simply a matter of having two different process people
check a reel change before implementing it in production.
But either way, what you do is you get rid of these blue defects and the net effect of that
is you end up with a distribution that has more separation and you end up with something
that looks like this at the end.
So you've got that there and then you've got this here and at that point, you can set your
threshold in the middle and then move it either left or right to put more risk on yourself
or on the customer depending on the nature of the application.
So there have been many books written on this topic and this is just kind of quick overview.
At the end of the video you will see some links where you can go for further information.
Thank you for watching.