University of ConnecticutComparison of THz Imaging with X-Ray

Kiarash Ahi, Navid Asadizanjani, Sina Shahbazmohamadi, Mark Tehranipoor and Mehdi Anwar

If you want to use these slides, please reference to our work:

K. Ahi, N. Asadizanjani, S. Shahbazmohamadi, M. Tehranipoor, and M. Anwar, “Terahertz characterization of electronic components and comparison of terahertz imaging with X-ray imaging techniques,” in . Proc. SPIE 9483, Terahertz Physics, Devices, and Systems IX: Advanced Applications in Industry and Defense, 94830X

(May 13, 2015).

https://www.researchgate.net/publication/278034592_Terahertz_characterization_of_electronic_components_and_comparison_o

f_terahertz_imaging_with_x-ray_imaging_techniques

Overview

Background and principles of THz pulse generation and detection for producing THz images

Experimental Setup in Transmission mode Applications of THz radiation in characterization of objects (refractive

indices, absorption coefficients) in Transmission mode Producing THz images in transmission mode: Using Attenuation

Coefficient and Time Delay

Experimental Setup in reflection mode Applications of THz radiation in characterization of objects (seeing

the different layers, that floppy disk, blacktopped ICs) in reflection mode

THz images in reflection mode: THz tomography

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Table of content

Classification of counterfeit electronic components; the green ticks indicates classes which are distinguishable by THz techniques

Background and principles of THz pulse generation and detection for building THz images

The first THz imaging system was introduced less than twenty years ago, in 1995 by AT&T Bell Laboratories .

Since pulsed femtosecond THz lasers were not commercially available until just less than two decades ago, THz imaging and THz spectroscopy have yet to find their roles in wide variety of applications.

THz techniques can be used for determining the materials in wide variety of objects from medicines to electronic components.

THz techniques have several advantages over other inspection and characterization techniques. THz radiation is non-ionizing and thus not only safer for human in compare to ionizing techniques like X-ray or gamma inspections but also nondestructive for electronic components and other objects.

THz imaging techniques

Transmission mode

Reflection mode

Images based on Attenuation

Images based on Phase (time) delay

Tomogram Images (based on Phase (time)

delay)

Experimental Setup: Transmission mode

Receiver

Transmitter

The Sample

15 20 25 30 35 40

-1.7

-1.6

-1.5

-1.4

-1.3

-1.2

-1.1

Time Delay[Picoseconds]

De

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ted

Pu

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e [

a.u

.]

Detected THz pulse after passing an IC

Detected THz pulse where no objects is palced Time delay Attenuation

The Sample

THz imaging techniques in transmission mode vs in reflection mode

(a) THz image of an IC of Figure 4 (a), The left image is obtained in reflection mode and the right one in transmission mode. (b) Color scale for TH images and the x-ray image of the IC (c) X-ray and THz images are superimposed.

Application: THz imaging techniques in transmission mode

(a) THz image of an authentic IC of Figure 4 (a) and its x-ray counterpart. (b) THz image of a counterfeit IC of Figure 4 (a) and its x-ray counterpart. (c) color scale for the THz images.

Asymmetry

Vertical die

Horizontal die

The transmitted THz pulse

The received THz pulse

X-ray

THz imaging techniques in reflection mode: Tomography

THz imaging techniques in reflection mode: Tomography

(a) THz image of the surface of an IC of Figure 4 (a) obtained in reflection mode. (b) THz image of the die of the IC obtained in reflection. (c) THz image of the leads of the IC obtained in reflection. (d) The color scale.

THz imaging techniques in reflection mode: Tomography

(a) THz image of the surface of an authentic IC of Figure 4 (a) and. (b) Its counterfeit counterpart.

The variance of the reflected THz from the surface of the counterfeit IC: 2.70×10-4 a.u. The variance of the reflected THz from the surface of the authentic IC: 1.17×10-4 a.u:

less than 45% of that of the counterfeit ICThe difference between the peak and the minimum value of the surface for the authentic IC: 0.061 a.u.The difference between the peak and the minimum value of the surface for the counterfeit IC: 0.076 a.u.:

25% higher than of the authentic IC

Conclusions

THz pulse lasers have not been commercially available until only two decades ago and thus THz techniques need to be developed for different aspects of science and engineering.

One of the highly promising fields for THz techniques is characterization and inspection via imaging of inside the objects.

It was also showed that, a wide variety of counterfeit electronic components are also distinguishable with THz techniques.

THz techniques are fast, economically reasonable, reliable, accessible for wide variety of consumers, nonhazardous and nondestructive.

Other techniques are mostly destructive, time consuming, hazardous to personnel, human dependent and thus expensive and with higher errors while THz is nondestructive, fast, safe for personnel and accurate.