scholarly journals Distance and Angle Correction System (DACS) for a kHz A-Scan Rate Pump-Probe Laser-Ultrasound Inspection

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7266
Author(s):  
Ryan A. Canfield ◽  
Jan Ahrens ◽  
Jill Bingham ◽  
Barry Fetzer ◽  
Thomas Müller-Wirts ◽  
...  
Keyword(s):  
Detection Efficiency ◽  
Numerical Aperture ◽  
Probe Laser ◽  
Depth Of Field ◽  
Polished Surface ◽  
Inspection System ◽  
Laser Ultrasound ◽  
Angle Correction ◽  
Ultrasound Inspection ◽  
Correction System

Non-contact optical detection of ultrasound critically depends on the amount of light collected from the detection surface. Although it can be optimized in multiple ways for an ideal flat polished surface, industrial non-destructive testing and evaluation (NDT&E) usually requires optical detectors to be robust for unpolished material surfaces that are usually rough and curved. Confocal detectors provide the best light collection but must trade off sensitivity with depth of field. Specifically, detection efficiency increases with the numerical aperture (NA) of the detector, but the depth of field drops. Therefore, fast realignment of the detector focal point is critical for in-field applications. Here, we propose an optical distance and angle correction system (DACS) and demonstrate it in a kHz-rate laser-ultrasound inspection system. It incorporates a Sagnac interferometer on receive for the fast scanning of aircraft composites, which minimizes the required initial alignment. We show that DACS performs stably for different composite surfaces while providing ±2° angular and ±2 mm axial automatic correction with a maximum 100 ms realignment time.

Detection of Solder Bump Defects in Electronic Packages Using Local Temporal Coherence Analysis of Laser Ultrasonic Signals

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Jin Yang ◽  
I. Charles Ume
Keyword(s):  
Solder Bump ◽  
Temporal Coherence ◽  
Acoustic Microscopy ◽  
Inspection System ◽  
Laser Ultrasound ◽  
Electronic Packages ◽  
Surface Mount ◽  
Flip Chips ◽  
Solder Bumps ◽  
Ultrasound Inspection

Microelectronics packaging technology has evolved from through-hole and bulk configurations to surface-mount and small-profile configurations. Surface mount devices, such as flip chip packages, chip scale packages, and ball grid arrays, use solder bump interconnections between them and substrates/printed wiring boards. Solder bumps, which are hidden between the device and the substrate/board, are difficult to inspect. A solder bump inspection system was developed using laser ultrasound and interferometric techniques. This system has been successfully applied to detect solder joint/bump defects, including missing, misaligned, open, and cracked solder joints/bumps in flip chips, chip scale packages, and multilayer ceramic capacitors. This system uses a pulsed Nd:YAG laser to induce ultrasound in the electronic packages in the thermoelastic regime; it then measures the transient out-of-plane displacement response on the package surface using the interferometric technique. This paper presents a local temporal coherence (LTC) analysis of laser ultrasound signals and compares it to previous signal-processing methods, including error ratio and correlation coefficient methods. The results showed that LTC analysis increased measurement accuracy and sensitivity for inspecting solder bump defects in electronic packages. Laser ultrasound inspection results are also compared with X-ray and C-mode scanning acoustic microscopy results. In particular, this paper discusses defect detection for 6.35×6.35×0.6 mm3 flip chips and flip chips (“SiMAF;” Siemens AG) with lead-free solder bumps.

Void Inspection in Lead-Free Solder Bumps on Ball Grid Array (BGA) Packages Using Laser Ultrasound Technique

2011 ◽  
Author(s):  
Jie Gong ◽  
I. Charles Ume
Keyword(s):  
Ball Grid Array ◽  
Lead Free ◽  
Inspection System ◽  
Laser Ultrasound ◽  
Lead Free Solder ◽  
X Ray ◽  
Bga Packages ◽  
Solder Bumps ◽  
Free Solder ◽  
Ultrasound Inspection

Solder joint voids are usually formed by the entrapped gas bubbles during the reflow process, and are common in all surface mount applications. It is a controversial issue on the reliability of the solder joint, however the consensus is that voiding is acceptable at low contents, while excessive voiding affects mechanical properties, and decreases strength, ductility and fatigue life of the interconnections. X-ray is the most widely used technique to evaluate the voids, including the size and occurrence frequency. In this paper, a laser ultrasound and interferometer inspection system is used to inspect the voids in lead-free solder bumps in ball grid array (BGA) packages. This system uses a pulsed Nd:YAG laser to induce ultrasound in the chip packages in the thermoelastic regime; and laser interferometer is used to measure the transient out-of-plane displacement response of the package surface to the laser irradiation. The quality of solder bumps is evaluated by analyzing the transient responses. In this work, voids were intentionally created by adding the volatile flux during the assembly process. By controlling the volume of flux dip, three different levels of voiding were proposed: void-free, relatively low and relatively high. The presence of voids in the solder bumps was first verified using 2-D X-ray techniques. Meanwhile, the built-in image-processing software in X-ray tool measured the void fraction to quantify the level of voiding. Then the laser ultrasound inspection system was used to evaluate the voids in these samples. By comparing the vibration responses from voided samples and void-free samples, it was found that the laser ultrasound inspection system is capable to differentiate samples with relatively high voiding from void-free samples while the relatively low voiding was below the resolution of the inspection system. Lastly, a further comparison between the void-free and voided solder bumps was carried out by the destructive cross-section technique. The comparisons between these three solder bump evaluation methods will be presented in this paper.

Board-Level Solder Joint Reliability Study of Land Grid Array Packages for RF Application Using a Laser Ultrasound Inspection System

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Jin Yang ◽  
Lizheng Zhang ◽  
I. Charles Ume ◽  
Camil Ghiu ◽  
George White
Keyword(s):  
Solder Joint ◽  
Thermal Cycling ◽  
Thermal Loading ◽  
Inspection System ◽  
Laser Ultrasound ◽  
Solder Joint Reliability ◽  
Joint Reliability ◽  
Joint Quality ◽  
Ultrasound Inspection ◽  
Board Level

Microelectronics packaging technology has evolved from through-hole, and bulk configuration to surface-mount, and small-profile ones. Today’s electronics industry is also transiting from SnPb to Pb-free to meet environmental requirements. Land grid array (LGA) package has been becoming popular in portable electronics in terms of low profile on the printed wiring boards and direct Pb-free assembly process compatibility. With the package profile shrinking and operating power increasing, solder joint quality and reliability has become a major concern in microelectronics manufacturing. The solder joint failure at the package level or board level will cause electronic devices not to function during service. In this paper, board-level solder joint reliability of the LGA packages under thermal loading is studied through thermal cycling tests. A novel laser ultrasound-interferometric system developed by the authors is applied to inspect solder joint quality during the thermal cycling tests. While the laser ultrasound inspection technique has been successfully applied to flip chips and chip scale packages, this study is the first application of this technique to overmolded packages. In this study, it is found out that the LGA packages can withstand 1000 temperature cycles without showing crack initiation or other failure mechanisms in the solder joints. The laser ultrasound inspection results match the visual observation and X-ray inspection results. This study demonstrates the feasibility of this system to solder joint quality inspection of overmolded packages. In particular, the devices constituting the objective of this study are radio frequency modules, which are encapsulated through overmolding and are mounted on a typical four-layer FR4 board through LGA terminations.

scholarly journals Shaping Beam Profiles Using Plastic Optical Fiber Tapers with Application to Ice Sensors

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2503
Author(s):  
Kostas Amoiropoulos ◽  
Georgia Kioselaki ◽  
Nikolaos Kourkoumelis ◽  
Aris Ikiades
Keyword(s):  
Fiber Optics ◽  
Optical Fibers ◽  
Laser Cooling ◽  
Detection Efficiency ◽  
Numerical Aperture ◽  
Beam Profile ◽  
Hollow Beam ◽  
Enhanced Sensitivity ◽  
Surface Irregularities ◽  
Plastic Optical Fibers

Using either bulk or fiber optics the profile of laser beams can be altered from Gaussian to top-hat or hollow beams allowing enhanced performance in applications like laser cooling, optical trapping, and fiber sensing. Here, we report a method based on multimode Plastic Optical Fibers (POF) long-tapers, to tweak the beam profile from near Gaussian to a hollow beam, by generating surface irregularities on the conical sections of the taper with a heat-and-pull technique. Furthermore, a cutback technique applied on long tapers expanded the output beam profile by more than twice the numerical aperture (NA) of the fiber. The enhanced sensitivity and detection efficiency of the extended profile was tested on a fiber optical ice sensor related to aviation safety.

scholarly journals Optical Projection Tomography Using a Commercial Microfluidic System

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 293
Author(s):  
Wenhao Du ◽  
Cheng Fei ◽  
Junliang Liu ◽  
Yongfu Li ◽  
Zhaojun Liu ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Numerical Aperture ◽  
Microfluidic System ◽  
Depth Of Field ◽  
Objective Lens ◽  
Flow Mode ◽  
Wide Field ◽  
Optical Projection Tomography ◽  
Microfluidic Systems ◽  
Optical Projection

Optical projection tomography (OPT) is the direct optical equivalent of X-ray computed tomography (CT). To obtain a larger depth of field, traditional OPT usually decreases the numerical aperture (NA) of the objective lens to decrease the resolution of the image. So, there is a trade-off between sample size and resolution. Commercial microfluidic systems can observe a sample in flow mode. In this paper, an OPT instrument is constructed to observe samples. The OPT instrument is combined with commercial microfluidic systems to obtain a three-dimensional and time (3D + T)/four-dimensional (4D) video of the sample. “Focal plane scanning” is also used to increase the images’ depth of field. A series of two-dimensional (2D) images in different focal planes was observed and compared with images simulated using our program. Our work dynamically monitors 3D OPT images. Commercial microfluidic systems simulate blood flow, which has potential application in blood monitoring and intelligent drug delivery platforms. We design an OPT adaptor to perform OPT on a commercial wide-field inverted microscope (Olympusix81). Images in different focal planes are observed and analyzed. Using a commercial microfluidic system, a video is also acquired to record motion pictures of samples at different flow rates. To our knowledge, this is the first time an OPT setup has been combined with a microfluidic system.

A Real-Time Inspection System Using a Terahertz Technique To Detect Microleak Defects in the Seal of Flexible Plastic Packages

2005 ◽  
Vol 68 (4) ◽  
pp. 833-837 ◽  
Author(s):  
YASUYUKI MORITA ◽  
ADRIAN DOBROIU ◽  
CHIKO OTANI ◽  
KODO KAWASE
Keyword(s):  
Detection Limit ◽  
Real Time ◽  
Refraction Index ◽  
Minimum Size ◽  
Inspection System ◽  
Absorption Coefficients ◽  
Polyethylene Films ◽  
Plastic Packages ◽  
Transmitted Signal ◽  
Ultrasound Inspection

A method to detect production faults in flexible plastic packages with the use of terahertz radiation is presented. Relying on the large difference between the absorption coefficients of plastic and water (for water-filled channel defects) and on the refraction index difference between plastic and air (for air-filled channel defects), our technique consists of focusing and scanning a terahertz beam on the sealed area of the package, followed by detection of the transmitted signal. Compared with previous methods, such as visual and ultrasound inspection, our technique can be applied to optically opaque packages and does not require immersion in a matching liquid. We tested our system on defects that we fabricated as water-filled and airfilled channels imbedded in polyethylene films, with diameters in the range of 10 to 100 μm. The detection limit (the minimum size of a detectable defect) depends on the conveying speed; this relationship was determined and analyzed. The results show that our system has the potential for application in an actual production line for real-time inspection.

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