Shrinking Size and Higher Density Require Advanced Inspection Techniques

The semiconductor industry continues to amaze and astound us with a steady stream of smaller devices that have increased functionality. And with this miniaturization comes some tough inspection and handling challenges.

Shrinking device size and increased circuit density mean that the highest stage accuracy and analytical and image resolution are needed for successful defect inspection, review, and characterization at the deep submicron level, said Patrick Finney, product marketing manager at FEI. The trend toward smaller components and products has been going on for years, but the extreme density of PCBs achieved recently are forcing manufacturers to reevaluate which inspection technologies to implement, said Mike Teska, product marketing manager at Hewlett-Packard. The traditional human visual-inspection approach no longer supplies the needed accuracy and repeatability.

Automated systems are required to generate detailed data needed for process improvement in production lines, said Dominic Haigh, business unit manager at Teradyne. The automated optical inspection (AOI) system has emerged as a solution for in-line process control. Recent advances in lighting, optics and image analysis have contributed to the success of AOI.

AOI systems provide the repeatability to find omitted, misaligned, rotated, and extra components as well as solder faults, agreed HP’s Mr. Teska. However, they require a sight line and cannot detect solder-joint defects on BGAs and flip-chip components with hidden solder joints under the device. Some manufacturers of complex PCBs are implementing automated X-ray inspection to check the integrity of the board, added Mr. Teska.

The increased density of components also leads to a thermal-management challenge, said Bruce Carocci, vice president of marketing at FLIR Systems. The trend is toward PC-based thermal-imaging systems that can support multiple tasks including verification of thermal modeling, failure analysis, and sample inspection of incoming parts.

Image Processing

The semiconductor industry needs better ways to manage design, test, inspection, and process data for use in yield enhancement, said Shawn Smith, product manager at Knights Technology. Semiconductor manufacturers require tools to process, correlate, and analyze the massive amounts of data generated by automated wafer probing and test systems.

Software is needed to bring together critical fab data, inspection results, and electrical test data, to help determine which processes or tools are contributing to yield loss. To do this, the software must integrate this data into process-control information to effect almost instantaneous process changes.

PC-based vision and image processing systems are realities now because of technological advancements such as faster CPUs, Intel’s MMX technology, the PCI local bus, and vision software and hardware, said John Hanks, analysis product manager for National Instruments. MMX technology has proven to be a windfall to PC-based vision software because it accelerates fixed-point arithmetic processes for multimedia. Some image-processing functions show as much as a 400% performance gain when run on a computer with MMX capabilities.

The maturation of the data-bus, processor, and operating-system technologies has paved the way for using the PC in many inspection applications, said Robert Gregory, product marketing manager at Data Translation. Combined with the lower cost of the PC, these are compelling reasons for manufacturers to use PCs in the inspection process.

Inspection Products

Automated Optical System

Has 0.5- and 1.0-mil Resolution

The AOI-190x AOI System provides PCB fabricators with off-line setup and verification capabilities. It offers 0.5-mil and 1.0-mil resolution, an 18″-wide inspection area, computer-automated machinery reference, a golden-board reference, and design rule logic. It supports a maximum throughput of 6 ft2/min. Reflective and transmissive light sources are used to inspect artwork and drilled holes. AOI International, (978) 937-5400.

UV Microscope Used for

Defect Classification

The Axiotron 2 Ultraviolet (UV) Microscope supports deep ultraviolet imaging used for defect classification of structures below 0.25 micron. It is optimized for 365-nm and 248-nm analysis. Images are captured with a cooled, high-resolution, UV-enhanced CCD camera. Navigation software helps position the scanning stage at the defect site. The system includes special reflected light UV optics, a UV light source, and a motorized wavelength changer. Carl Zeiss, (800) 233-2343.

Thermal Video System

Has 0.025°C Resolution

The TVS-8000MkII Series Thermal Video System features a 0.025°C temperature resolution and a frame time of <1/60-s. A detector microcooler provides a stable operating temperature to achieve extended cool life cycles and low noise. Objects down to 10 µm can be measured using the optional microscope set. The Model TVS-8100MkII has a temperature measurement range from -40°C to 300°C; the temperature range of the TVS-8200MkII is -40°C to 1,200°C. Cincinnati Electronics, (800) 852-5105.

X-Ray Fluorescence System

Measures Coating on PCBs

The XRX X-Ray Fluorescence System measures the coating thickness on PCBs. The system efficiency and speed now are enhanced with the Windows 95 operating system and the company’s SmartLink Pro software. The fluorescence system is available with a 12″ × 12″ × 6″ programmable stage. CMI International, (800) 678-1117.

Automated X-Ray System Finds

Shorts, Opens, Misalignments

The CRX-2001 BGA Buster™ finds incorrect ball shapes and sizes, missing balls, shorts, opens, and misalignments. The system also verifies chip-packaging interconnects, ultra fine-pitch components, and tape automated bonding. It has a password-protected Windows 95-compatible interface, X-ray sources with levels to 160 keV, and focal-spot sizes <2 µm. A rotational plate allows the board-under-test to rotate in three dimensions. Test results can be integrated into a production control network. CR Technology, (714) 448-0443.

System Combines Laser

And PC-Based Interface

The LSM2™ SMT Inspection System combines noncontact laser-measurement technology with a PC-based interface. Typical PCB assembly applications include measuring wet solder paste, checking stencil aperture size, and inspecting solder joints. The system measures width, length, and height and uses the data to calculate averages, area, and volume. Live images of the measurement site are displayed on a color monitor at one of two magnification levels. CyberOptics, (800) 746-6315.

Frame Grabber Features

On-Board Scaler

The DT3154 is a 24-bit, color frame grabber for the PCI bus. It features a composite sync output, a full on-board scaler, and a digital clock synchronization circuit that limits pixel jitter to ±4 ns. Composite sync output helps synchronize multiple external cameras from a single source, allowing you to switch between cameras without loss of vertical synchronization. The Sync Sentinel™ circuit improves degraded VCR images by ignoring extra sync pulses and inserting sync pulses that are missing. The board interfaces with RS-170 NISC and PAL/CCIR RGB video. It also has a 2:1 multiplexed input that allows selection between two cameras with one board. Data Translation, (800) 525-8528.

Dual-Beam FIB/SEM Station

Performs 3-D Defect Review

The XL830™ FIB/SEM Workstation offers a 3-D defect review capability and characterization tools. The system’s scanning electron microscope (SEM) column provides 3- nm resolution from 1 kV to 30 kV. The electron column offers balanced-field, in-lens detection, down-hole visibility, and enhanced grain boundary imaging. Focused ion beam (FIB) milling for cross-sectioning and imaging with the SEM are simultaneous operations. The Predictive User Interface™ tool keeps the submicron defect in the field of view during various operations. FEI, (503) 640-7500.

X-Ray System Has

30° Directional Target Tube

The FXS-100.11 X-Ray System Series offers a 30° directional target X-ray tube with a minimum focus-to-object distance of 6 mm. The system inspects components as well as populated PCBs at the highest magnification of 90×. The X-ray controller, manipulator, and video image are integrated as an image field and image overlay on the system monitor. FeinFocus, (818) 889-1440.

System Provides

Real-Time Imaging on PC

The Tracer™ Thermal Imaging System records and analyzes thermal-event sequences at real-time frame rates up to 60 Hz on a Windows-based PC. The system includes the company’s Prism DS infrared camera, a Pentium®-based PC, a digital recording system, and software. It records 5+ min at a 60-Hz frame rate with 12-bit pixels, capturing 9.3 MB of data/s. The Tracer senses temperature differences of <0.1°C @ 30°C and measures temperatures from -10°C to +2,000°C with an accuracy of ±2%. FLIR Systems, (800) 322-3731.

System Inspects

Flip-Chip Components

The HP 5DX Model 5400 Automated X-Ray Inspection System, based on cross-sectional imaging technology, assesses the structural integrity of a solder joint on a component with a pitch as small as 0.2 mm. The system has an automated in-line capability and can inspect a PCB every 60 to 90 s. The 5400 includes an enhanced X-ray tube with a more tightly focused X-ray beam, a digital camera, and a high-resolution scintillator. Hewlett-Packard, (800) 452-4844.

Automated Optical System

Checks for Process Faults

The Innovate 3000 AOI System checks for process faults on PCBs. The system has up to 48 CCD cameras on each side of the board. Double-sided, mixed-technology boards can be inspected prior to solder reflow and wave solder. Pattern-recognition algorithms help determine features, locations, quality, angle, and contrast of components. The system is available in an in-line and a manual-feed version. Failure information can be automatically linked to real-time process monitoring and rework tools. A bar-code interface accepts data for board serialization. Innovate, (888) 798-0556.

Machine Vision System

Inspects LCDs

The machine-vision-based LCI-Professional System inspects liquid-crystal, dot- matrix, seven-segment, and vacuum-fluorescent displays. It is used on the production line to check the displays of cellular phones, pagers, electronic organizers, calculators, and radios. The PC-based system supports 8-bit monochrome and 24-bit color inspection. It checks for shorts, failed icons, single pixel faults, back-illumination failures, poor contrast, and character generator failure. Integral Vision, (248) 471-2660.

Failure Analysis Reference

Provides Process Guidance

The FA Wizard™ Software Module provides chip makers with training methods for problem-solving during semiconductor design, production, packaging, and field use. It offers flow charts for analysis assistance and provides on-line failure-analysis reference and access to more than 60 analysis technique modules. The software consists of process flow chart, reference, and failure mechanism code modules. Knights Technology, (408) 988-0600.

Microscope Features

115-mm Working Distance

The LEICA GZ6T Microscope has a conductive body that provides static protection for inspection and assembly of electronic components. It can dissipate 1,000 V to ground in 0.05 s. Optical features include a 115-mm working distance, 6.7× to 40× magnification, a 360° rotating body, and a one-turn zoom range. Leica, (800) 248-0123.

Mini Mirror Helps

Inspect BGAs

The Ball Grid Array Mirror helps inspect the outer and inner rows of solder balls on a mounted BGA device. The mirror is hand-held or self-standing and measures 0.754″ L × 0.190″ W. A diamond coating helps protect the mirror from scratching. Metron Optics, (619) 755-4477.

Image Acquisition Board

Designed for Mac Computer

The IMAQ PCI-1408 Image Acquisition Board is a PCI-based board for Macintosh computers. The IMAQ product line includes driver software and the company’s IMAQ Vision software for image acquisition, process, and analysis. PCI-1408 can be used for a number of applications including motion measurements, caliper and gauging, identification, inspection, real-time process control, assembly verification, wafer inspection, and bar-code reading. An 8-bit flash A/D converter changes video signals to digital format. The board acquires images up to 30 frames/s. National Instruments, (800) 258-7022.

Single-Cassette Loader

Used for Wafer Inspection

The NWL-860 Wafer Loader handles 150-mm to 200-mm wafers and allows operators to perform micro and macro inspection routines. The loader provides front and side as well as periphery and center backside macro inspection. Inspection parameters for wafer rotation, speed, and tilt angle are carried out in the manual or the automatic mode and controlled by a joystick. Nikon, (800) 52-NIKON (526-4566), ext. P7034.

Confocal Microscope Uses

Nipkow Disk Module

The MX50-CF Real-Time Confocal Microscope integrates specialized optics with a Nipkow Disk Module to inspect multilayered semiconductor structures. It resolves images of <0.25 µm. The microscope offers two confocal, confocal with the Nomarski differential interference contrast, and brightfield modes. Mercury and Xenon light sources are available for confocal observation. Olympus, (800) 455-8236.

Optical System Supports

Variety of Working Distances

The Fixed Magnification Optical Systems are used for applications requiring magnified images on a CCTV monitor. The systems have a combination of function modules, working distances, and fixed lens tubes for three camera formats. The camera formats are available in 1/3″, 1/2″, and 2/3″ sizes. Five fixed tube options range from 23.4 mm to 164.8 mm, and five working distances of 50 mm, 90 mm, 130 mm, 150 mm, and 190 mm are offered. Function modules support internal focus, coaxial illumination, and a variable working-distance lens. Magnifications range from 0.30× to 3.31× with standard function modules. Optem International, (716) 223-2372.

Programmable Lens Provides

10:1 Zoom Capability

The Zoom-X Lens offers a 10:1 programmable zoom function for the company’s line of SmartScope MVP Video Inspection Systems. It provides constant image brightness regardless of magnification. The lens comes with MeasureMind Plus software with field-of-view image processing. Built-in optical limit switches and software controls ensure zoom elements never reach the mechanical limits of travel. Optical zoom magnification is 0.7× to 5.5×, and the on-screen range is 25× to 200×. Optical Gaging Products, (800) 647-7627.

Laser Scan Technique Covers

Only Points of Interest

The RVSI 7000 Series is a laser inspection system and handler. It uses the company’s in-tray SmartScan™ technology to place laser data points on only the critical features requiring measurement, skipping regions of no interest. The approach employs a segmented receiver that eliminates the corruptive effect on measurements caused by spurious reflections. The receiver masks out undesirable laser data that is reflected from adjacent features. The 7000 Series uses two elevated inspection areas and a tray inversion module that makes visual inspection possible on the top and bottom of a device in a single pass. RVSI Electronics, (516) 273-9700.

Metrology System Inspects

Photomasks and Magnetic Heads

The AMS 250 Metrology System inspects and measures photomasks, magnetic heads, and wafers. It is a single-axis tool based on the company’s proprietary metrology technology. The system features automatic measurement, focus, and illumination control. It uses transmitted and brightfield reflected illumination modes. On-screen magnification is 8,500× with a 150× objective. Accuracy per the NIST SRM473 requirements is <±0.015 µm. Technical Instrument, (408) 434-1000.

Optical Inspection Systems

Offer New Camera-Head Designs

The Interscan 5539 and 5529 Series Automated Optical Inspection Systems provide visual inspection of components and solder paste on loaded PCBs. They are used during pre- or post-solder wave and post-reflow or post-placement of components. The 5539 Series features a new five-camera head design comprised of one vertical and four angled cameras. The 5539 A+ model has a 0.4″ field of view (fov), and the B+ model is equipped with a 1″ fov for inspecting 50-mil pitch components. Teradyne, (617) 482-2700.

Wafer Measuring System

Has 0.1-µm Sensitivity

The WM Series of wafer-surface particle measuring systems automatically detects particles on the surface of a wafer at 0.1 µm using scattered laser light technology. The WM-1500 and WM-1700 systems provide a dynamic measurement range of 0.1 to 5.0 microns. Particle detection applications include process and equipment monitoring, engineering analysis, yield improvement, and clean-room monitoring. Topcon Technologies, (201) 261-5410.

SMT Measurement System

Makes 3-D Inspections

The SVS 8100 SMT Measurement System characterizes screen-printing and component-placement processes. It acquires, analyzes, and displays 3-D information at acquisition rates of 4 in.2/s. Measurements include solder-paste volume, area, height, X-Y coplanarity, and bridge detection. Placement measurements for X/Y shift and theta and checks for presence/absence of components are performed. The system checks for coplanarity of paste, and BGA and QFP devices. View Engineering, (805) 578-5000.

Copyright 1998 Nelson Publishing Inc.

February 1998

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