Potential of Non Destructive Evaluation Techniques for DUNE Cold Electronics QA/QC Leonard J. Bond, Professor of Aerospace Engineering & Director, CNDE Zhan Zhang, Scien?st, CNDE Dan Barnard, Scien?st, CNDE Chien-Ping Chiou, Scien?st, CNDE Jonathan Eisch, postdoc, Dept. of Physics & Astronomy Navaneeth PoonthoEathil, postdoc, Dept. of Physics & Astronomy Frank Krennrich , Professor, Dept. of Physics & Astronomy Amanda Weinstein, Assoc. Professor, Dept. of Physics & Astronomy 1 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Mo>va>ons � Non destruc?ve evalua?on techniques may be useful for detec?ng defects that do not show up in func4onal tests. � Iden?fy defects that arise from chip/board manufacturing or from stresses due to thermal cycling. � Spa?al resolu?on of NDE techniques —> chip inspec?on. � BNL provided us with ADC ASIC samples: a blind search for defects. � X-ray, terahertz and acous?c microscopy: have different capabili?es. � Nature and size of defects of interest: without knowing that it is very difficult to select and op?mize am inspec?on approach. � Suitability depends on defect: delamina?on, cracks, voids, marginal wire bonds. 2 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Samples (BNL) Good … Bad … Retest F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
X-ray Scans � X-rays sensi?ve density — solder voids, insufficient solder, marginal wire bonds, connec?ons, board manufacturing defects. � Resolu?on of current setup: 20 micron, 2-d scanning. � Can be improved to 1 micron via upgrade of X-ray source. � PCB/BGA specific planar CT/Laminography: limited 3-d view for flat objects (chips, boards) planned (moving X-ray source and detector). � Status : scanned several chips, work is ongoing. � Next steps : visit with GE Inspec?on Technology Customer Center to demonstrate their commercial laminography system with our chips. 4 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
X-ray Scans 5 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
X-ray Scans � Next: compare all 27 chips. � Use CAD file for the ASIC and produce simula?on to evaluate sensi?vity of laminography for detec?ng cracks/delamina?ons. res. 20 micron Courtesy of Zhan Zhang 6 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Terahertz Scans � Reflectometry: layers with different refrac?ve index reflect terahertz signal — technique can probe deep into device, except for metallic layers. � Two resolu?ons of current setup: a) lateral ~ 200 micron, b) through thickness resolu?on ~ capable of detec?ng delamina?ons. � Scans an en?re board in 1/2 hour. � Commercial scanners: ~ 1 micron resolu?on. � Scans provide a view into different depth of device by analyzing the train of pulses in the digi?zer. � Status : 12 chips scanned, show some differences but requires further analysis. 7 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Terahertz Scans non-DUNE board 8 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Terahertz Scans res. 200 micron non DUNE FPGA 9 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Terahertz Scan (front): ADC ASIC 10 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Terahertz Scans (from the back) Gated at back surface of chips Gated at mid layer inside chips THz Courtesy of Chien-Ping Chiou F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Acoustic Microscopy � Likely the most sensi?ve technique to detect delamina?on in chips. � Resolu?on depends on wavelengths: 30 MHz — 50 micron, GHz — 0.2 micron but penetra?on depth is reduced at shorter wavelengths. � Current CNDE imaging system: Connected to pulser/receiver and A/D for data capture —> 100 MHz — 15 micron. T/R water sample 12 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Acoustic Microscopy time=2 x path in water/velocity in water Amplitude (v) BW 2 t Courtesy of Dan Barnard BW 1 FW t 0 13 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Acoustic Microscopy Additional reverberations also occur. Here, right, we see the echo arriving first back to the probe as FW (front wall echo), with BW 1 and BW 2 (the 1 st reverberation of the back wall) following. This happens with external surfaces as well as internal defects. These effect occur where the ultrasound energy is contained in a planar propagating or in a focused beam (the result of a focusing element on the probe). Focusing has two benefits: it increases the flux at the focus to effectively increase the gain of the system, and also increases spatial resolution (the beam diameter is smallest at the focal zone). The graphic below demonstrates the response captured by the system A/D. Time t 0 represents the beginning of the measurement, and the time to the FW and subsequent echoes is a function of the paths and velocities involved. As can be seen, the echo amplitude decreases in each echo, a result of losses from T&R across interfaces as well as attenuation (scattering and absorption) and beam spread. The below waveform is referred to as an A-scan time=2 x path in water/velocity in water Amplitude (v) Courtesy of Dan Barnard BW 2 t BW 1 FW t 0 14 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
15 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Summary � Exploring 3 different NDE techniques for poten?al use on QA/QC for DUNE cold electronics system. � X-ray technique for evalua?ng of stuffed boards and solder connec?ons poten?ally with 0.5 micron resolu?on (3-d). � Terahertz reflectometry and acous?c microscopy are used to search for defects at the chip level. 3D Computed Tomography of an USB flash drive (GE) Technique selec?on and op?miza?on will depend on the nature and � size of the defects of interest (unknown). 16 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
Backup Slide (Correla?on Search) Y Because we don’t know what is the cause of the failure in the chips, it’s location and size with respect to the ultrasonic beam in the part, we don’t know what features to key off of X in the images. So, we need some type an analysis that is objective/repeatable rather than using our subjective eyes to evaluate the images for differences. Gate A correlation approach can be used. Here, we would apply correlation analysis to the individual A-scans captured during ultrasonic scanning. An explanation follows. C-scan full waveform data The full waveform data collected in a C-scan is shown represented as a 3D data set, where each vertical column of the (X,Y) raster scan is one A-scan. A typical C-scan image is produced by gating a particular region of each A-scan and displaying the peak amplitude in the gate for all (X,Y) positions in the scan. A-scan Courtesy of Dan Barnard 17 F. Krennrich Update on NDE techniques for Cold Electronics QA/QC
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