Inspecting and Analyzing Printed Circuit Boards Quickly and Reliably with a Digital Microscope

AUTHORS

James DeRoseScientific Writer, Stereo & Digital Microscopy Marketing,

Leica Microsystems AG, Switzerland

Georg SchlafferProduct Manager, Digital Microscopy, Leica Microsystems AG, Switzerland

From Eye to Insight

MICROELECTRONICS TECHNICAL REPORT PART 1

MICROELECTRONICS PART 1: INSPECTING AND ANALYZING PRINTED CIRCUIT BOARDS QUICKLY AND RELIABLY WITH A DIGITAL MICROSCOPE

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Why Inspection with a Digital Microscope?

For the past several years, digital microscopy has been shown to be useful for inspection, quality control and assurance (QC/QA), and failure

analysis (FA) in the microelectronics industry, especially for printed circuit boards (PCBs). Recently, state-of-the-art improvements have made

digital microscopy even more powerful and practical for inspection, leading to a more efficient workflow. Here, the advantages of certain

digital microscope features, i.e., intuitive software for operation and analysis, fast and easy ways to change magnification, and encoding for

reliable recall of parameters, are explained.

Digital microscopes are optical microscopes operated without eyepieces; the image is observed directly on an electronic display. The Leica

DVM6 digital microscope provides users with an even easier and more rapid way to record high quality, reliable image data and make quick

analysis leading to greater efficiency when inspecting microelectronic parts.

Which Features of a Digital Microscope Lead to Reliable Analysis and Greater Workflow Efficiency?

Multiple features of the Leica DVM6 make it easy to use and render the inspection and analysis workflow more efficient:

> Intuitive software for microscope operation and data analysis;

> Efficient, simple way to change magnification over the entire range (12:1 to 2350:1);

> Encoding (automated tracking and storing) of important parameters, e.g., stage, optics, illumination, and camera settings, for rapid recall

at any time;

> Fast and easy microscope head tilting and sample rotation;

> Integrated LED (light-emitting diode) ring light and coaxial illumination allowing versatile contrast;

> High performance digital camera with fast live image and 10 MP resolution; and

> Software enabled/supported capture modes, e.g. XY and XYZ stitching and high-dynamic-range (HDR) etc.

This report discusses how the first 3 points above contribute to a faster, more reliable workflow.

3MICROELECTRONICS PART 1: INSPECTING AND ANALYZING PRINTED CIRCUIT BOARDS QUICKLY AND RELIABLY WITH A DIGITAL MICROSCOPE

Quick and Easy to Setup and Get Started

Operation of the Leica DVM6 digital microscope only requires a power cable and a USB cable connected to a computer running the Leica

Application Suite X (LAS X) software. Once an objective lens is in place, the Leica DVM6 is ready to perform inspection, QC/QA, and FA.

The maximum working distance is 60 mm, the sample stage travel range is 70 x 50 mm, and the maximum sample weight is 2 kg.

Below is a photo of the Leica DVM6 digital microscope with a PCB (printed circuit board) placed onto its stage, as well as a photo of the

PCB, and a low magnification DVM6 image of a region of it.

Printed circuit board (PCB) used as sample.

Leica DVM6 digital microscope with PCB (printed circuit board)

sample on stage.

Low magnification image of a part of the PCB sample recorded

with the Leica DVM6.

MICROELECTRONICS PART 1: INSPECTING AND ANALYZING PRINTED CIRCUIT BOARDS QUICKLY AND RELIABLY WITH A DIGITAL MICROSCOPE

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Measurement, Analysis, and Operation with Intuitive Software

In order to achieve a faster and reliable workflow for inspection, QC, and FA with a digital microscope, an intuitive software package with

numerous functions for microscope control, simple yet flexible image acquisition, and sample analysis is essential. For example, the software

used with the Leica DVM6, Leica Application Suite X (LAS X), offers storage of multiple user profiles for cases where many different users

work with the same microscope. The Z-stack function of LAS X enables users to record images in various focal planes over a defined Z-range

for a sample feature or the entire sample itself. The extended depth of field (EDOF) mode provides a multi-focus image without the need to

set begin nor end levels. Both Z-stack and EDOF allow the fast creation and analysis of 3D topographic surfaces [1] of a sample.

In addition, with LAS X software, users can choose different modes for a large XY scan, such as “mark & find,” “tile scan,” and “spiral scan.”

An interactive mode called “Live Image Builder” for XY (2D image), Z (3D image), and XYZ (3D image over extended area) can also be used.

Examples of 3D sample analysis using LAS X are shown below with a PCB (printed circuit board) and SMD (surface mounted device) hybrid

sample. Report generation with just one click is also explained.

3D image of a portion of a PCB showing integrated circuit (IC) chips

and a solder joint; captured with a Leica DVM6 using the EDOF

(extended depth of field) function of LAS X. See also same image on

the right with color Z-scale.

Same 3D image as on the left with color Z-scale.

2D image of part of a PCB showing a capacitor and a bit of an IC

chip. Captured with a Leica DVM6 using EDOF. See on the right the

3D image of this PCB region.

3D image of the same PCB region as one the left. Various

measurements, such as step height, angle, and volume, have been

made.

5MICROELECTRONICS PART 1: INSPECTING AND ANALYZING PRINTED CIRCUIT BOARDS QUICKLY AND RELIABLY WITH A DIGITAL MICROSCOPE

2D image of part of an SMD hybrid with transistors or diodes. Captured with a Leica DVM6 using EDOF.

3D image of the SMD part shown on the left. Various measure-ments, such as profile, step height, and volume, have been made.

2D image of part of a PCB showing an IC chip and a capacitor. Captured with a Leica DVM6 using EDOF. See on the right the 3D image of this PCB region.

3D image of the PCB region shown on the left. Measurements of area, volume, step height, length, etc. have been made. A report is created as an excel file by clicking “export” (marked by the yellow box).

Created report from measurements: summary tab of excel file showing 1st page of report with 2D image of PCB region.

Created report from measurements: image tab of excel file showing measurements and 3D image of PCB region.

MICROELECTRONICS PART 1: INSPECTING AND ANALYZING PRINTED CIRCUIT BOARDS QUICKLY AND RELIABLY WITH A DIGITAL MICROSCOPE

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Fast Magnification Change over a Large Range

The objective lenses of the Leica DVM6 are quickly and easily changed during operation of the instrument with essentially no increase

in workflow. This online video shows how simple it is to switch objectives [2].

There is a selection of 3 plan apochromatic (chromatic correction over the red, green, and blue wavelengths and flatness correction

over the whole field of view) objectives (low, middle, and high magnification). There is also the 16:1 integrated zoom optics with which

users can achieve total magnification values from 12:1 to 2350:1 (with the recommended 27 inch (69 cm) diagonal monitor display in

accordance with the standard ISO/DIN 18221) [3]. The zoom optics works with each of the 3 objectives for low, middle, and high

magnification, making it possible to change the magnification in a continuous manner over the full range.

It must be kept in mind that the final magnification value for digital microscopy will depend on the monitor size used for image display

[3]. As mentioned above, it is recommended that the Leica DVM6 be operated with a 27 inch (69 cm) diagonal monitor. Images of an

electronic sensor acquired with the Leica DVM6 using the low, middle, and high objective at low, middle, and high magnification are

shown below.

Leica DVM6 image of an electronic sensor: low magnification

range (low objective).

Leica DVM6 image of an electronic sensor: middle magnification

range (middle objective).

Leica DVM6 image of an electronic

sensor: high magnfication range (high

objective).

7MICROELECTRONICS PART 1: INSPECTING AND ANALYZING PRINTED CIRCUIT BOARDS QUICKLY AND RELIABLY WITH A DIGITAL MICROSCOPE

Encoded Parameters of the Leica DVM6 Digital Microscope

An instrument with hardware in direct communication with computer software to allow the automatic tracking and saving of specific

parameters is called an “encoded” device. Encoding is very useful for rapidly recalling parameters and settings stored during data

acquisition. Encoding is invaluable for reproducibility and reliability and also contributes to a more efficient workflow.

For the Leica DVM6, the objective and zoom optics, camera pixel resolution, sample stage position and rotation angle (whether manual or

motorized movement), microscope head tilt angle, and illumination system settings are encoded and stored via LAS X software. An example

of the encoding of some of these parameters during operation of the Leica DVM6 is shown below.

Operation panel of LAS X for the Leica DVM6. The total magnification value (19x, <2.00> is the zoom factor) from objective

and zoom optics, microscope head tilting angle (5°), and stage rotation angle (20°) are encoded. The same parameters are

also displayed in the lower right corner.

Lower right corner of LAS X panel above. The field of view (FOV) or object field (marked by

the green rectangle in the images above) is also encoded (objective and zoom optics).

MICROELECTRONICS PART 1: INSPECTING AND ANALYZING PRINTED CIRCUIT BOARDS QUICKLY AND RELIABLY WITH A DIGITAL MICROSCOPE

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T +41 71 726 34 34 . F +41 71 726 34 44

www.leica-microsystems.com

Conclusions

More efficient, reliable inspection, quality control and assurance (QA/QC), and failure analysis (FA) for microelectronics parts, such as

printed circuit boards (PCBs), is achieved with the Leica DVM6 digital microscope. Here three of its benefits were discussed: intuitive

software with many functions for microscope operation, image capture, and data analysis; convenient ways to change magnification

rapidly over the full range from 12:1 up to 2350:1; and encoding of all important parameters and settings (optics, camera, stage, head,

and illumination) for easy, fast recall. These features allow Leica DVM6 users to make faster and reliable data acquisition and analysis

for greater inspection, QC, and FA workflow efficiency.

Additional Reading

1. D. Goeggel, G. Schlaffer, 3D Visualization of Surface Structures, Vertical Resolution – Small Steps, Big Effect, Science Lab; Leica

DVM-3D Visualisation; Vertical resolution in the balance between numerical aperture and depth of field

2. Objective change: plug and see, Leica DVM6 product page

3. J. A. DeRose, M. Doppler, Is a Magnification of 20,000 Times Really Useful With Digital Microscopy?; J. A. DeRose, M. Doppler,

What Does 30,000:1 Magnification Really Mean? Some Useful Guidelines for Understanding Magnification in Today’s New Digital

Microscope Era, Science Lab

Copyright© by Leica Microsystems (Schweiz) AG, CH-9435 Heerbrugg, 10/2015. Subject to modifications. LEICA and the Leica Logo are registered trademarks of Leica Microsystems IR GmbH.