Operation X-ray Update

X-Ray Provides a Picture of Imperfection

A couple of months ago Circuit Technology Center had the good fortune to obtain a Dage 7500 X-Ray machine.  For years we had been using a 2D (two dimensional viewing; x and y) machine that has been an absolutely reliable workhorse.  Since we loved our old machine, we didn't immediately recognize what the Dage (or any other the new generation of 2D x-ray machines) could do for us, but when we saw how it performed, well, all I can say is, "What an eye opener!"

Figure 1: Old machine void view.

Figure 2: New machine void view.

The Dage 7500 is one of the new breed of 2D machines that can rotate the beam receiving head up to 70 degrees from perpendicular making the Dage more like a 2 and a half D machine.  Take a look at the following images.

Figure 1 is from the old 2D machine and Figure 2 is from the Dage.In both figures one can note a sizable void in the ball, but in the new machine we can get a better view of the characteristics of the void; its size, location and scope.   In Figure 3, I tilted the board in the older machine to see if I could duplicate the view of the Dage and as you can see, it doesn't come close.

Figure 3: Old machine angled view of void.

Figure 4: Backed off image on old machine.

The angling of the head in the Dage provides perspective on the ball and void that is just not available in the older machine.  Additionally it is hard not to notice the clarity of the image which is part of the reason we are able to magnify the image without distortion

Frequently customers ask us to take a backed off x-ray shot a BGA component just to have a record of the component appearance post-assembly.  In Figure 4 you can see the distortion at the edges of a 42.5 MM component in the picture taken with the old machine.

On the other hand, as you can see in Figure 5, the component maintains its form in the photo.  Further, in practice, the Dage pictures maintain their clarity when the customer zooms in to examine specific features.

Figure 5: New machine backed off image of same component.

Figure 6: Void and ball measurement on from the new machine. The void diameter is about .4 MM and the ball itself is .86 MM.

Another nice feature of the new machine is the ease of measurement.  On the old machine, a somewhat laborious calibration was required prior to accurate measurement.  On the Dage, it's measure at will.  In the case of the void we focused on earlier, you can get a quick view of the size of this void relative to the size of the overall ball in a heartbeat.  See FIgure 6.

Figure 7: Dage machine measures relative size of subject and adjacent balls. The center ball with the void is .86MM and the two side balls are .76MM. Quite a blowout!

Further, if you are wondering what affect this void (a blowout caused by outgassing from a fault in the integral via) has on the size of the ball here is an interesting comparison between this ball and its immediate neighbors. In Figure 7(see below), you can see the void is large enough to dramatically increase the size of the ball's perimeter. Finally, one of my favorite pictures is of a different ball from a side view.  In this Figure 8, we can see the top and bottom pads and the location of small voids in the ball.

Figure 8: Side view of defective ball. The top pad (slight rim of a shadow), bottom pad (clear and light image) and a void are pointed out in near 3-D clarity.

We still haven't explored the expansive capabilities of this new machine.  There are measurement and comparison routines for ball, through-hole and void measurement and other automatic features we don't completely appreciate yet, but as you can see from the images above we are already reaping the benefits of the upgraded technology.  There are a number machines (if you search the internet you will come up with a wide variety of reputable companies - we just happen to have the Dage) that provide this angled type viewing and we are quite enthusiastic about the advantages these new machines provide.  If you want to improve your view of x-ray images from the old straight shot 2D imager, I highly recommend you give this type of machine serious consideration.

Several members of the Circuit Technology Center team contributed to this feature story.