Circuit World

Influences on the reflow soldering process by components with specific thermal properties : Table of Contents

Florian Schüßler, Denis Kozic, Jörg Franke — Sun Jul 26 14:15:03 BST 2009

Abstract:
Purpose – The purpose of the paper is to focus on the research into components with specific thermal properties and their influences on the reflow soldering process. Design/methodology/approach – After a brief introduction, the paper gives an overview of the necessity of thermal management on printed circuit boards (PCBs) and the possible effects on the manufacturing of electronic devices. In the next sections, different test boards are presented for investigations into different thermal effects during soldering. The last section deals with the influences of molded interconnected devices (MIDs) on the reflow soldering process. Findings – The investigations show that components from the thermal management influence the reflow soldering process more or less. The highest impacts on the soldering process are from components with a thermal connection to the electrical component and its solder joint. All results from the investigations have in common that the thermal influence can only be compensated by increasing the temperature during soldering. However, this significantly increases the risk of overheating the electrical components or the PCB itself. Research limitations/implications – This paper shows only the influence of some of the effects caused by thermal management on the reflow soldering process. Furthermore, vapour phase soldering is not considered, but actual investigations are carried out on vapour phase soldering ovens as well. Originality/value – Thermal management becomes more and more important with the increasing functionality of electrical components and electronic devices. This topic has been the subject of a large number of articles. However, this paper deals with influences that thermal management has on the soldering process during the manufacturing of the electronic device.

EnFACE: a maskless process for circuit fabrication : Table of Contents

Sudipta Roy — Sun Jul 26 14:15:03 BST 2009

Abstract:
Purpose – The purpose of the paper is to present an update and the latest results from work on a project which could be useful for maskless printed circuit board (PCB) manufacturing. Design/methodology/approach – Copper is plated and etched using a novel electrochemical technique, electrochemical patterning by flow and chemistry, using a masked tool and fully exposed substrate. The micro patterns on the tool are replicated on the substrate via optimum design of the apparatus, choice of electrolyte chemistry and fluid flow. Findings – Linear and square shapes ranging from 5 to 200?µm are transferred using the technique by electrochemical plating and etching. Up to 25 substrates could be processed using a single tool, which indicates that photolithography requirements can be greatly minimised. Research limitations/implications – The copper lines are transferred to relatively small substrates. The process needs to be scaled up to accommodate larger substrates in order to fully exploit its potential for PCBs. Originality/value – The paper presents a fundamentally different approach to transfer micron scale pattern using a maskless technology. The platform technology involves using a mask to pattern each substrate; this work shows that micron scale patterns can be transferred without masking by optimising electrochemical reactor technology.

The processing time optimization of printed circuit board : Table of Contents

Mircea Ancau — Sun Jul 26 14:15:03 BST 2009

Abstract:
Purpose – The purpose of this paper is to demonstrate the optimization of printed circuit board (PCB) manufacturing by improving drilling process productivity. Design/methodology/approach – Two different ways are explored to increase the productivity of the PCB drilling operation. The first way involves the minimization of the cutting-tool path length. The second way to achieve the objective explores the efficiency of processing stacked PCBs. Findings – To reduce the tool path length between the holes of a PCB, a heuristic hybrid algorithm to solve the traveling salesman problem (TSP) is briefly described. Also, a mathematical model to calculate the total processing time is proposed. Based on this model, the paper shows the optimal number of stacked PCBs that can be profitably processed, while high processing productivity does not always mean high number of stacked PCBs. Research limitations/implications – The paper does not treat the optimization of the drilling process parameters, even if reduction of the drilling time using optimized cutting parameters also represents an efficient method for improving the productivity. Originality/value – The paper shows the influence of the algorithm performance for solving the TSP on the processing time minimization, by decreasing the component of drill movement time along the drill path between holes. Additionally, the conditions in which stacking a specific number of PCBs is advantageous are also investigated. Furthermore, the paper shows how to determine the optimum number of stacked PCBs.

Halogen-free materials with improved thermal and electrical properties : Table of Contents

David Bedner, Michael He — Sun Jul 26 14:15:03 BST 2009

Abstract:
Purpose – The purpose of this paper is to present a latest update on halogen-free base materials that are lead-free compatible and have enhanced electrical properties. Design/methodology/approach – Numerous halogen-free flame retardants are screened in laboratory conditions for a wide arrange of properties. Once suitable candidates are found, they are compounded and processed into copper-clad laminates and a wide variety of properties are tested. Findings – Several formulations are found that are lead-free compatible and that has enhanced electrical properties. Surprisingly, some thermal properties are found to be superior to traditionally halogenated laminates. Research limitations/implications – The research here only presents the halogen-free properties of a bare, unpopulated printed wiring board with no build up of inner layers and devoid of solder mask. Further work needs to be done on full circuit assemblies to properly evaluate the impact of removing halogens from interconnecting packages. Originality/value – The paper details the material property differences between various halogen-free materials as compared to halogenated materials. A method to model composite properties is also discussed.

Microfluidic systems on a printed wiring board platform : Table of Contents

Sun Jul 26 14:15:03 BST 2009

Abstract:
Purpose – The purpose of this paper is to present the development of printed wiring board (PWB)-based microfluidic building blocks and their integration into systems for DNA amplification and electronic detection. Design/methodology/approach – Technologies from embedded passives (EP) and photolithographic high-density interconnect are integrated into a traditional PWB platform to enable multifunctional electrochemical sensors for on-chip detection of biological assays. Findings – PWB materials and processes can be applied to develop microelectromechanical systems (MEMS) and microfluidic systems. On-chip heaters using EP have been demonstrated with excellent accuracy. The on-chip heaters can be used for localized temperature control as well as heat air pumps. The integration of EP and microchannels is a promising approach to add functionalities to the PWB-based microsystems. Research limitations/implications – Further integration of microchannels with the embedded heaters and electrochemical sensors will increase the compactness, functionality, and value of the PWB-based microfluidic systems. Originality/value – The paper describes the development and integration of PWB-based building-blocks such as EP and microchannels for MEMS and microfluidic applications. These elements will enable new applications and enhanced functionalities of PWB.

Method and system of automated measurement of micro drill bit wear : Table of Contents

Lianyu Fu, Jian Li, Fan Yang — Sun Jul 26 14:15:03 BST 2009

Abstract:
Purpose – The purpose of this paper is to provide a method and system to achieve automated measurement of micro drill bit wear. Design/methodology/approach – A method and system of automated measurement of micro drill bit wear on the basis of machine vision are presented. Experiments are conducted to verify the developed method and system. Findings – The worn area of the primary face is an appropriate index to reflect the wear condition of a micro drill bit. A machine vision based technique is an applicable tool for capturing and characterising images of worn micro drill bit. The developed system can accurately measure and characterise the wear performance of micro drill bits with different materials and different parameter designs. Originality/value – The paper highlights the method and the system for achieving automated measurement of micro drill bit wear. The developed method and system can provide fast and precise evaluation of micro drill bit wear.