Help building an digital x-ray system / Electromagnetic Radiation / Forums

Forums

4hv.org :: Forums :: Electromagnetic Radiation

« Previous topic | Next topic »

Help building an digital x-ray system

1 2 3 4 next

Move Thread

LAN_403

Mon Mar 08 2010, 03:14AM

Registered Member #2721 Joined: Fri Mar 05 2010, 04:09PM
Location: Guadalajara, Jalisco
Posts: 28

Hello,
i want to build a digital xray system to check solder joints on BGA devices, i have a couplle of questions, i hope someone can help on this. in advance, Thanks.

1.- To produce Xray as far as i have read the lowest voltage usable is 60Kv, is this right ?

2.- Would a Mazzilli flyback driver circuit and voltage multiplier provide enough current at the HV required to produce xrays??

3.- Can a xray tube be used in cold cathode emission mode?

4.- is the glow from a xray cassete intensifier be seen by the naked eye under dim light ?

again, thanks for your help

Proud Mary

Mon Mar 08 2010, 09:20AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Ed wrote ...

Hello,
i want to build a digital xray system to check solder joints on BGA devices, i have a couplle of questions, i hope someone can help on this. in advance, Thanks.

1.- To produce Xray as far as i have read the lowest voltage usable is 60Kv, is this right ?

2.- Would a Mazzilli flyback driver circuit and voltage multiplier provide enough current at the HV required to produce xrays??

3.- Can a xray tube be used in cold cathode emission mode?

4.- is the glow from a xray cassete intensifier be seen by the naked eye under dim light ?

again, thanks for your help

1. Usable for what exactly? X-ray tubes are manufactured in a range of flavours from 5kVp and less to 5MVp and more.

2. Yes.

3. Special tubes are made to operate via field emission, especially 'flash' X-ray tubes.

4. Not something I'd want to try - but direct vision fluoroscopes were widely used in medicine until the mid-1950s, when their danger to both patient and operator became clear. The human eye itself is able to 'see' bright X-ray sources as a blue glow, a discovery made in the very early days of Roentgen rays, though the exact mechanism of action remains unknown. *

As for 'digital' X-radiography, Flat Panel Detectors, whether amorphous Silicon, or amorphous Selenium, are fiendishly costly.

* Frame, Paul. "Wilhelm RÃ¶ntgen and the Invisible Light". Tales from the Atomic Age. Oak Ridge Associated Universities.

hboy007

Mon Mar 08 2010, 11:54AM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374

you could put both an intensifier sheet and the circuit board in a flatbed scanner and just "scan" the image after you have disconnected the light source.

IntraWinding

Mon Mar 08 2010, 04:34PM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
Posts: 581

There was a similar idea out there using a modified flat bed scanner to input the spectrum from a diffraction grating.

I think they had fool it into thinking the light source was working before it would scan.

I've found it on the Wayback Machine.
"A Simple Slitless Spectrograph Based on Desktop Scanner Parts"

But if you're going to all the trouble of building an X-Ray machine, why not use a digital camera to capture the images from the fluorescent screen?

Proud Mary

Mon Mar 08 2010, 07:07PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

IntraWinding wrote ...

if you're going to all the trouble of building an X-Ray machine, why not use a digital camera to capture the images from the fluorescent screen?

The safest way to do this is via a right-angle prism and suitable lenses - a periscope - so that the X-ray do not impinge directly on the digital camera. Direct irradiation will generate noise in the CCD/CMOS sensor, and may fizzle some of the pixels.

hboy007

Tue Mar 09 2010, 12:00AM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374

I just re-read your inital post. If you only need let's say 4x4 cmÂ², the best solution might not be a flat bet scanner but something like Proud Mary suggested. You may want to evaluate the following setup:
your x-ray source is in a properly shielded box also containing the sample. A cheap but usb controllable still frame camera observes the reflection of an intensifier screen below the sample. Use first surface mirrors for best results. An old digital SLR might be the thing you are looking for in respect to resolution - and save some bucks for a decent macro lens ^_^

Proud Mary

Tue Mar 09 2010, 01:35AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

hboy007 wrote ...

Use first surface mirrors for best results. An old digital SLR might be the thing you are looking for in respect to resolution - and save some bucks for a decent macro lens ^_^

A first surface mirror offers none of the radiological protection of a prism and lenses made from high refractive index glasses containing 25% Pb or Th.

Moreover, a rectangular box-like structure with an X-ray source at one end is an open invitation to grazing reflection - the reflection of X-rays which occurs when their angle of incidence is less than ~2 deg. Scattering from ambient air molecules and airborne particulates would add an extra dimension of hazard unless taken care of, and also reduce the resolution of the final image.

You would have to have an awful lot of ball grid arrays to inspect in order to justify all these expenses! But good luck to you.

Wed Mar 10 2010, 03:37AM

Registered Member #2721 Joined: Fri Mar 05 2010, 04:09PM
Location: Guadalajara, Jalisco
Posts: 28

Fist of all Thanks to all for your comments,

now on to start doing something, the idea for now is to place the x-ray source then PCB then intensifier screen, then leaded glass and last a digital camera under USB control for safety the whole thing will be enclosed in a wooden box covered by 1/4 inch lead sheet on the outside and operated from a distance.

does this sound feasable to start with ???

i guess so, so on to the actual PSU, (Flyback driver)
i have a couple of HGTG30N60A4D IGBT'S, and two 24volt 50A SMPSU's what modifications should be done to the attached schematic (credit to Vladimiro Mazzilli), and what is the best way to setup the PSU's in series or parallel ?

Thanks !!

Thu Mar 11 2010, 04:09AM

Registered Member #2721 Joined: Fri Mar 05 2010, 04:09PM
Location: Guadalajara, Jalisco
Posts: 28

Some advance made, PCB ready, waiting for comments on component values

Thanks

Proud Mary

Thu Mar 11 2010, 02:49PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Ed wrote ...

Some advance made, PCB ready, waiting for comments on component values

Thanks

Don't you think you might be putting the cart before the horse here?

Wouldn't it be more useful to first determine the time integral of the X-ray photon flux density needed to image your ball grid arrays?

Without this fluence figure, you will not be able to determine the specs of the X-ray tube you will need to do it, whether an
anti-scatter grid will be needed, whether fixed or variable grids may be needed for the selected source to subject distance, and so on.

Finally, if you do not specify the X-ray tube, you cannot know what its PSU requirements will be, nor the thickness of shielding
it will require, nor its costs.

1 2 3 4 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob