Quality Alchemist (品質煉金術師): Seminar on Characterization Methods for PCB Industry

The seminar entitled “Characterization Methods for Printed Circuit Board (PCB) Industry” was organized by Hong Kong Science and Technology Parks (HKSTP) and co-organized by The Hong Kong Electronic Industries Association (HKEIA) on 7 Jan 2011. This seminar focused on some critical PCB manufacturing processes, studies of PCB reliability, and some analytical tests that were useful for PCB material laminate characterization. Some modern surface analysis techniques such as XPS, AES and ToF-SIMS as effective tools for solving problems related to metal surface finish in PCB were discussed.

The first speaker was Dr. Winco Yung (Asso. Professor of ISE, PolyU; Honorary Advisor, Hong Kong Printed Circuit Association – HKPCA; Center-in-charge, PCB Technology Center, PolyU) and his topic was “PCB Laminate Characterization and Quality Assurance”.

Dr. Yung presentation included PCB Lamination Technology, Common Defects in Lamination, Type of PCB Laminates, Material Characterization, Reliability Test and Case Study.

Firstly, Dr. Yung introduced the multi-layer fabrication. It begins with the selection of an inner layer core- or thin laminate material of the proper thickness. Cores could very from 0.038” to 0.005” thick and the number of cores used would be depended upon the board’s design. The basic materials of multi-layer board included copper foil, prepreg and inner-layer cores (copper foil and Glass fiber & resin).

Then the laminate panels bonded together under heat and pressure.

The typical pressing profile was shown.

The following common defects included Bow & Twist, Delamination, Blister, Measling, Misregistration, and Other defects were discussed.

I. Bow & Twist

II. Delamination

III. Blister

IV. Measling

V. Misregistration

The first five defects were summarized in the following table.

VI. Other defects

Other defects were summarized.

Then Dr. Yung briefed different type of PCB laminate such as FR4 (most economic), Halogen Free, High Speed and Flexible Materials.

After that Dr. Yung mentioned those materials characterization included:
1. Thermal properties
- Glass Transition Temperature (Tg) using TMA (Thermo-mechanical Analysis): Higher Tg, Higher Cost
- Coefficient of Thermal Expansion (CTE): Low CTE (z-axis)
- Decomposition Temperature (Td): High Td, Higher final product reliability

2. Electrical properties
- Dielectric constant (Dk) affect the signal speed
- Dissipation factor (Df) affect the signal integrity

Reliability Test for PCB (Thermal Shock, Interconnect Stress, Conductive Anodic Filament and Time to Delamination Test) was also discussed.

Conductive Anodic Filament (CAF) failure was the growth or electro-migration of copper in a PCB. The test was reference to the standard IPC-TM-650 2.6.25.

The micro graph for dendrite growth during CAF related test was showed.

The video showed the dendrite growth.

Finally, Dr. Yung discussed three case studies to us.

After the presentation, the souvenir was presented to Dr. Yung.

(Left: Dr. Raymon Chan (Specialist, MAL-HKSTP), Dr. Winco Yung and Ms.Trace Chan (Head – Membership & Promotion, HKEIA))

Then Dr. Winco Yung and I took a photo for memory. Dr. Winco Yung was past HKSQ ex-co member & Hon Treasurer. We had recognized in HKSQ since 1997.

The second speaker was Dr. Cindy Xi (Specialist, MAL – HKSTP) and her topic was “Applications of surface analysis techniques including SEM/EDX, AES, XPS, ToF-SIMS, Surface profilometer, AFM, FTIR and XRF for PCB industry”.

Dr. Xi introduced each analysis techniques and its application in Material Analysis Laboratory (MAL) at HKSTP. Some equipment were showed in following photos.