Greening PCB Drilling Process: Burr Minimization and Other Strategies Funding Sources: Korea Institute of Industrial Technology
Authors: Huang, Y., Linke, B., Bhandari, B., Ahn, S. and Dornfeld, D.
Yu-Chu Huang © 2011 LMAS
contact email:
[email protected]
Motivation
Information Flow Diagram
■ The hole drilling step is important in the manufacturing of Printed Circuit Boards (PCB). It influences the shape of burrs and the deburring process. Minimizing drilling burr can reduce effort and time for deburring, and therefore decrease energy consumption for the whole process.
■ The general goal of the project is to develop an energy-saving manufacturing process for information technology (IT). ■ The research consortium:
Inter Layer Image Transfer Circuit Design Photoresist Coating UV Exposure
Pro-clean
Photoresist Coating
UV Exposure
Resist Develop
Copper Etch
Resist Strip
Electroless Copper
Deburr and Scrub
Hole Desmear
Hole Drilling
Laminate inner Layers
Oxide Treatment
Pattern Plate Copper
Resist Develop
Pattern Plate Etch Resist
Photoresist Strip
Copper Etch
Etch Resist Strip
Final Fabrication
Nickel Gold Plating
Hot Air Solder Level Process
Solder Mark Application
Outer Layer Image Transfer
- What we are focusing The process flow diagram for manufacturing PCB
Quantification and Optimization Based on LCA KAIST/NIST
PMU Diagram and Configurable EMS KITECH/U-Bot INC PMU Diagram and Configurable EMS KITECH/U-Bot INC
Demo Site1 BM Korea Co., Ltd
Demo Site2 KOFCO
Information exchanged with SNU
Cu Entry board Cu
Bakelite PCB PCB
Epoxy
Backup board
■ Process parameters
Accelerometer
• • • • • • •
Drilling stack
PCB
Quality Management, Simulation and Process Optimization KITECH/CAU
Experiment Setup
■ What is a printed circuit board (PCB)?
GFRP
Optimization and Fusion Process Tech for Forging U of Ulsan/U of Hannover
Surface Finish
Background PCB
Design Tech for PCB Process SNU/UCB
History and outlook for the global printed circuit industry Figure source: Prismark PCB report 2010 2nd quarter
■ The global market size of PCB products in 2009 was $44.4 billion and is projected to register about $76.2 billion by the year 2015. Every enhancement of energy consumption or environmental friendliness of PCB manufacturing will benefit the global PCB market and our environment.
Types of Drilling Burr
Bit diameter: 400μm Spindle speed: 90000 rpm In-feed speed: 40 mm/sec Hits: 790 hits (2000hits) Sampling frequency: 20 kHz (low 9 kHz) Sampling time: 5 sec (x3) Sensors: 3-axis dynamometer, 3-axis accelerometer • Stacks: 3 layer • Entry board: Al • Backup board: wood
Spindle
Dynamometer
Drilling experiment setup
Common drilling tool f400 mm
Simplified experiment setup
Drilling Burr Control Chart
■ Two types of drilling burr were defined: ■ Uniform burr had relatively small and uniform burr height, ■ Transient burr was large and irregular. It is the transition stage between the uniform burr and drill breakage.
■ Drilling Burr control chart (DBCC) quantifies the effect of feed rate and spindle speed on burr type. A DBCC is proposed as a tool to assist prediction and control of drilling burr under given drilling conditions. Drilling Burr Control Chart for PCB
Figure source: Bhandari et al., “Development of micro drilling burr control chart based on Taguchi methods for PCB drilling,” Asian Symposium for Precision Engineering and Nanotechnology 2011
■ The major process parameters which influence the burr size and shape observed in experiments are feed and spindle speed.
Tool Life
1 drilling tests
■ Transient burr is preferred. To minimize the drilling burr, the green points in the figure are the generally recommended ranges of cutting parameters.
Future Work
■ As burr size increased with the number of holes drilled, the exit burrs required a deburring operation. st
A dimensionless feed parameter of drilling, 𝐹𝐹𝑛𝑛 = 𝑓𝑓/𝑑𝑑 The cutting speed parameter, 𝑆𝑆 = 𝐾𝐾 × 𝑑𝑑 × 𝑁𝑁, 𝐾𝐾 = 10−5 𝑓𝑓: feed 𝑑𝑑: drill diameter 𝑁𝑁: spindle speed
After drilling tests (790th hit)
Assumed burr size curve and new burr size curve for proposed cutting condition
■ Quantifying the effect of drill geometry and drill wear on the drilling burr formation ■ Improving burr quantification methods
Wear on the top of drill
■ Analyzing relationships among process parameters and energy ■ Constructing energy saving knowledge of PCB drilling
Drilling Burr
■ Increasing the energy efficiency for drilling ■ Reducing PCB drilling lead time Figure source: Min, S., PhD Thesis, UC Berkeley, 2001.
■ If the deburring operation needs to be kept, then the tool life can be increased. Conversely, if we eliminate the deburring process, then lowering feed can reduce the burr size. Then trade-offs is possible between reduced drilling process productivity and decreased deburring effort.
