Ahi terahertz 1

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Terahertz Characterization of Electronic Components 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/

Transcript of Ahi terahertz 1

Terahertz Characterization of Electronic Components

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

Tra

nsm

issi

on m

ode

Ref

lect

ion

mod

e

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.

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

tec

ted

Pu

ks

e [

a.u

.]

Detected THz pulse after passing an IC

Detected THz pulse where no objects is palced Time delay Attenuation

The Sample

Refractive index

The fraction of the speed of light in the vacuum, c, in compare to its speed in a material, v, is defined as refractive index, n:

(1)

Which gives equation (2) to be used for calculating the refractive index of the ICs in this experiment setup.

(2)

Where:

cn

v

1c t

nT

c: speed of light in the vacuum

v: speed of light in the material

Δt: The measured time delay and

T: The Thickness

Attenuation coefficient

By equation (3) the attenuation coefficient in units of dB/cm can be calculated:

Where:

1020(log ) 8.7ea a

(3)1020(log ) 8.7e

a a

0

1ln z

a

A

z A (4) 0

a zzA A e (5)

µa: amplitude attenuation factor

A0: amplitude of the

traveling wave

Az: attenuated amplitude of

the traveling wave z: transmitter to the

receiver axis

and

Characterization Based on Refractive Index and Attenuation Coefficient

Refractive Index of the Authentic ICs at 1 THz :

1.79

Refractive Index of the Counterfeit ICs at 1 THz :

1.82

Attenuation Coefficient of the Authentic ICs at 1 THz :

2.263×104

Attenuation Coefficient of the Counterfeit ICs at 1 THz :

2.475×104 dB/cm

Characterization Based on Refractive Index and Attenuation Coefficient

Broadband terahertz characterization of the refractive index

Variations of refractive indices of materials in different THz frequencies can give a signature to characterize them.

In the following Figure refractive indices of two authentic ICs and their counterfeit one are depicted.

Interestingly, the refractive indices of the authentic ICs are the same in the THz frequency domain while that of the counterfeit one stands out.

2

THz techniques in reflection mode

The transmitted THz pulse

The received THz pulse

X-ray

Distance between the different layers of an object

Having the refractive index (calculating it using the method in transmission mode) one can calculate the distance between the surface, the die and the leads using the equation (7).

Where θ is calculated by equation (8).

In this experiment and thus . Substituting the values into equation (7) gives the thickness of the layer between the surface and the die as 766 μm which is in consistence with results of the thickness measurements of x-ray tomography.

121

1

cos2

td

n

1 1 1

2

sinsin ( )

n

n

(7)

(8)

Discrimination of Blacktopped IC

THZ:Using equation (7) and the refractive index for organic materials gives the thickness of the blacktopped layer as 250 μm.

X-ray tomography:Blacktopping materials are transparent to x-ray, thus x-ray tomography imaging cannot be used for distinguishing the blacktopped components.

Other Techniques:Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive X-ray Spectroscopy (EDS), Scanning electron microscopy (SEM) and scanning acoustic microscopy (SAM) can be used but these are more time consuming than THz, expensive and mostly destructive.

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.