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Article
Publication date: 1 March 1989

F.W. Haining, R.F. Shaul, R.W. Keim and R.M. Murcko

The circuit elements of every printed circuit board have the potential for failure during test and/or use. These failures can occur by forming short‐circuits between adjacent…

Abstract

The circuit elements of every printed circuit board have the potential for failure during test and/or use. These failures can occur by forming short‐circuits between adjacent circuit elements, or by forming open‐circuits in the conductors. The risk sites can be identified by type, and the total number enumerated by manual inspection of the photolithographic masks used to fabricate the printed circuit layers. However, the circuit density of high performance printed circuit boards has become so great that meaningful manual analysis has become impractical. A more effective method is to use special graphics programs to analyse the computer‐aided design (CAD) data. The methodology developed to perform the CAD analysis of high performance printed circuit boards for short‐circuits utilises two powerful computer graphic tools: the Interactive Graphics System and the Unified Shapes Checking system. Test data for open‐circuits are generated using specially written alphanumeric routines. The data can be used for stress testing the printed circuit boards by wiring up special test modules that are plugged into the boards and then placing the boards into environmental test chambers. The printed circuits are checked for short‐circuits by putting them into groups that have no risk of shorting to each other (zero risk), and placing the groups in parallel under an electrical potential. The flow of current between the groups would indicate a short‐circuit. Similarly, the printed circuits can be checked for open‐circuits, by stringing them together into groups in series, and measuring the changes in resistance under thermal stress. Both types of test data can also be used for in‐process testing.

Details

Circuit World, vol. 15 no. 4
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 April 1989

M. Weinhold

Printed (circuit) boards have been used in the electronics industry for the past 25 years and more. The technology used to design and manufacture PCBs is well known and accepted…

Abstract

Printed (circuit) boards have been used in the electronics industry for the past 25 years and more. The technology used to design and manufacture PCBs is well known and accepted. Recently, however, designers of electronic equipment have shown that the use of newer materials and systems, such as flexible and moulded circuits, hybrid circuits, or a combination of these, can significantly improve the cost/performance ratio for electronic interconnects. This paper examines some of the many possibilities open to electronics designers and how these new opportunities can improve the economics and performance of electronic equipment.

Details

Circuit World, vol. 16 no. 1
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 April 1985

S. Kalenik and B. Anderson

This paper presents an experience in designing a printed circuit board prototype as part of a general surface mount investigation for commercial electronics application. The point…

Abstract

This paper presents an experience in designing a printed circuit board prototype as part of a general surface mount investigation for commercial electronics application. The point of view is that of a low volume assembler of relatively large, complex PC boards which use standard components. Three prototype versions were designed using different criteria. FR‐4 substrate was used for all of the designs. A comparison of the three designs with the through‐hole version indicates that the economic success of surface mounted printed circuit assemblies is heavily dependent on the physical design of the printed circuit board. Some of the aspects of a surface mounted circuit assembly that are discussed include design philosophy and tools, printed circuit board fabrication and bare board test. Design practices that would ideally utilise the small size of surface mount components are contrasted with those practices necessary to provide low cost and manufacturability of the printed circuit board.

Details

Circuit World, vol. 12 no. 1
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 December 1997

M. Huschkta

Higher performance, higherreliability and low cost are the key requirements for today's and tomorrow's printedcircuit boards for SMT and COB applications. The successful…

152

Abstract

Higher performance, higher reliability and low cost are the key requirements for today's and tomorrow's printed circuit boards for SMT and COB applications. The successful implementation of an improved FR‐4 system of the second generation will explain how all three can be met.

Details

Circuit World, vol. 23 no. 4
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 1 March 1992

J. Glazer, P.A. Kramer and J.W. Morris

The effect of gold (Au) on the reliability of 0.65 mm pitch surface mount solder joints between plastic quad flat packs and Cu‐Ni‐Au FR‐4 printed circuit boards was investigated…

Abstract

The effect of gold (Au) on the reliability of 0.65 mm pitch surface mount solder joints between plastic quad flat packs and Cu‐Ni‐Au FR‐4 printed circuit boards was investigated. Cu‐Ni‐Au is a desirable printed circuit board finish for multi‐chip modules or printed circuit boards that would otherwise require a selective Au finish, for example for edge connectors or wire bondable parts. However, Au is known to embrittle solder when it is present in sufficiently high concentrations, creating a concern that solder joint fatigue life in service will also be adversely affected. This paper reports the results of mechanical shock, mechanical vibration and thermal cycling testing of fine pitch solder joints containing varying amounts of Au. Tests were performed on as‐soldered joints and on joints that had been heat‐treated to evolve the microstructure towards equilibrium. The tests were designed to accelerate in‐service conditions in a typical industrial environment. Under these conditions, the Au concentrations tested did not promote solder joint failures. Microstructural characterisation of the distribution and morphology of the Au‐, Ni‐ and Cu‐Sn intermetallics in the joint before and after accelerated testing was also performed. On the basis of these observations it is recommended that the Au concentration in solder joints between plastic quad flat packs and Cu‐Ni‐Au FR‐4 printed circuit boards not exceed 3.0 wt.%.

Details

Circuit World, vol. 18 no. 4
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 February 1986

S. Gazit

The increasing use of high switching speed systems in both microwave electronics and high speed logic devices has created the need for printed circuit boards which are based on…

Abstract

The increasing use of high switching speed systems in both microwave electronics and high speed logic devices has created the need for printed circuit boards which are based on low dielectric constant and low loss materials. In addition, these circuit materials must be capable of withstanding elevated temperatures typical of hostile service environments and of board fabrication processes. Such low dielectric constant rigid boards are commercially available from a few sources. However, there is a growing demand for low dielectric constant flexible printed circuit boards for interconnecting rigid boards or in rigid/flex applications where high speed, fast rise times, controlled impedance and low crosstalk are important. A new family of thin laminates which are suitable for fabrication of flexible low dielectric constant printed circuit boards have been developed by Rogers Corporation. These circuit materials are called ROhyphen;2500 laminates and offer flexible interconnections in high speed electronic systems. RO‐2500 circuit materials are based on microglass reinforced fluorocarbon composites and have a typical dielectric constant of 25. The transmission line properties of these materials have been evaluated by the IPC‐FC‐201 test method. The results indicated that these circuit materials improve the propagation velocity by about 10% and the rise time by about 30% when compared with the same geometry, polyimide film based, flexible PCs in stripline constructions. Also, dimensional stability of these laminates after etch and heat ageing is improved over that of the standard flex circuit materials based on polyimide film. RO‐2500 laminate properties have been evaluated by the IPC‐TM‐650 test methods, which are widely accepted by the flexible PCB industry.

Details

Circuit World, vol. 12 no. 3
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 10 May 2013

Hongyan Shi and Hui Li

The purpose of this paper is to present a clear picture of the challenges of micro drill bit and the developments of novel micro‐drill bits for flexible circuit boards

Abstract

Purpose

The purpose of this paper is to present a clear picture of the challenges of micro drill bit and the developments of novel micro‐drill bits for flexible circuit boards, environmental‐friendly printed circuit boards (PCBs), high aspect ratio drill bit and ultra‐small micro drill bit, as well as the developments of geometry design of micro drill bit.

Design/methodology/approach

The paper details the developments trend and challenges of micro drill and PCBs first. Then the current research status of novel micro drill bits for flexible circuit boards, environmental‐friendly PCBs, high aspect ratio drill bit, ultra‐small micro drill bit are described. Finally, the developments of geometry design and drilling process are reviewed.

Findings

To achieve excellent performance for drilling flexible PCB, a large helical angle, large flute/land ratio and small web thickness that guarantee the sharp evacuation capability, are adopted in drill bit design. A small helix angle and an appropriate primary face angle are employed for drill bit to process environmental‐friendly printed circuit boards. It is beneficial to implement big helix angle, small primary face angles and small point angles in the design of ultra‐small micro drill bit. An optimum web thickness and step feed should be taken into consideration in high aspect ratio drill bits design.

Originality/value

The paper reviews different solutions of micro drill bits for the state‐of‐the‐art PCB and the developments of geometry design of drill bit for printed circuit boards.

Article
Publication date: 1 April 1983

H.R. Shemilt

Close spacing of conductors, surface mounted components and a multiplicity of DIPs have rendered the use of heat sinks on the PC board surface more and more hazardous. Where…

Abstract

Close spacing of conductors, surface mounted components and a multiplicity of DIPs have rendered the use of heat sinks on the PC board surface more and more hazardous. Where exposure to extreme temperatures is likely, the bond of heat sinks to the board has failed in 8% of cases during a recent investigation. Using the techniques described in this paper, any company with a multilayer manufacturing capability can produce a printed circuit board with good thermal conductivity and expansion characteristics related to most component mounting devices.

Details

Circuit World, vol. 10 no. 1
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 June 1995

David Golding

Discusses the manufacturing technology associated with the assembly ofprinted circuit boards [PCBs] covering photolithography, etching,manual assembly of PCBs and the soldering…

465

Abstract

Discusses the manufacturing technology associated with the assembly of printed circuit boards [PCBs] covering photolithography, etching, manual assembly of PCBs and the soldering methods involved. Describes how all the stages of PCB assembly can be automated and also looks at how the boards are cleaned and tested. Concludes that many factors need to be taken into account when deciding which method of manufacturing printed circuits would be best suited to a company’s requirements.

Details

Assembly Automation, vol. 15 no. 2
Type: Research Article
ISSN: 0144-5154

Keywords

Article
Publication date: 1 February 1986

J.J. Tomaine

The arrival of Large Scale Integration (LSI) devices forced the development of products which could reliably package these high density chip carriers. Until LSI, printed circuit

Abstract

The arrival of Large Scale Integration (LSI) devices forced the development of products which could reliably package these high density chip carriers. Until LSI, printed circuit technology designers were only moderately challenged to make high density products. This change occurred in the early 1970s at IBM with the printed circuit packaging for the IBM 4300 models. This was the first system application of LSI chip carriers. Since then, numerous LSI printed circuit carrier designs have been used in IBM systems. The methods to predict reliability of the LSI printed circuit carriers have not kept up with the hardware technology. This paper will describe an enhanced method of prediction which more closely represents the performance of today's LSI printed circuit cards and mother boards. Computer processed algorithms will be used to estimate the failure rates of a particular printed circuit carrier and the effects of this estimate on the complete system will be discussed. The estimation algorithms are contained in programmes resident on floppy diskettes and run on an IBM Personal Computer. The flexibility and ease of use of the PC allows the user to make any necessary additions or changes to the algorithms quickly. The algorithms are derived from standard Weibull reliability techniques but include internally derived factors which enhance the accuracy of the Weibull predictions. Data from extensive field reporting of any defects and detailed failure analysis are used to enhance the accuracy of the algorithms. Using the enhanced algorithms, one can generate new estimates easily. Quick access and fast turnaround times result in a convenient and cost effective technique to provide these estimates to system users on a timely basis. Design changes to the carrier which could affect the reliability are quickly modelled in the algorithms and new reliability estimates are provided allowing the final user to make the required system trade‐offs easily. These design changes and new reliability projections can be presented to management in a timely manner and allow them to make the cost/performance decisions which result in the optimum marketable product.

Details

Circuit World, vol. 12 no. 3
Type: Research Article
ISSN: 0305-6120

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