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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.

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.

It was observed that “no solder” or “skipped solder” defects occurred on a particular printed circuit board assembly product during wave soldering. Investigations were carried out to find out the cause of this defect and to recommend an optimal hot air level coating thickness. To evaluate whether thicker plating helps to produce better solderability, new printed circuit boards with an average plating thickness of 4.27 μm were sent for solderability testing. This increase in plating thickness resulted in no defects in the solderability test. This is in contrast to the current printed circuit board that had a no/skipped solder defect rate of 1,433 ppm due to the thinner plating thickness which was in the region of 2.26 μm. In summary, the investigations made have revealed imperfections in the pad plating, and it is recommended that a thicker or more even plating is achieved during the hot air levelling process at the printed circuit board manufacturing site so as to eliminate no/skipped solder defects that are induced by this printed circuit board deficiency.

BS 9760 and three sectional specifications for rigid printed circuit boards have now been published. The Institute's representative on BSI Technical Committee ECL/19 outlines the new standard system and shows that it offers a good opportunity of achieving international status. The future of BS 4025, the best known British Standard for printed circuit boards, BS 4597 and the interim Defence Standards is limited. The author appeals to Institute members to support ECL/19 in its work of ensuring that the printed circuit producer and user have meaningful and cost‐effective standards.

The printed circuit board version, ‘packlayer’, represents an alternative to printed circuit boards with conventional solder mask systems which is not yet widely known. This alternative type does, however, offer some considerable advantages in comparison with printed circuit boards with solder resist, with the result that the higher cost involved is thoroughly acceptable. Through the development of a new system called ‘Low‐Cost‐Packlayer’, bearing the special name MeSoMask, a variant has emerged within the packlayer sector. This special version combines the advantages of the packlayer with the costs of a conventional solder resist system and therefore presents a genuine alternative to the normal printed circuit board.

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.

This paper aims to evaluate the influence of previous exposure to moisture on delamination and formation of CAF (conductive anodic filament) in printed circuit boards used for lead‐free soldering.

The moisture absorption and desorption characteristics of printed circuit boards were evaluated according to the IPC/JEDEC J‐STD‐020C standard for handling of moisture sensitive components. The CAF test was performed according to IPC‐TM‐650, Test Method 2.6.25.

Printed circuit boards used for lead‐free soldering must be treated as moisture sensitive components. Severe delamination occurred on test boards that had been exposed to JEDEC level 1 conditions prior to soldering, while no delamination was observed on boards exposed to level 3. Furthermore, previous moisture and thermal exposure had a strong influence on CAF formation. The insulation resistance dropped three decades in less than 15 h in the worst case.

There are considerable stresses on printed circuit boards in lead‐free soldering processes. The influence from materials and processes is very large on the CAF formation. Therefore, a useful strategy is to evaluate the CAF properties for each supplier and material.

The paper pin‐points previous moisture exposure as a very important factor for delamination and CAF formation and confirms that printed circuit boards must be treated as moisture sensitive components.

An overview has been presented on the topic of alternative surface finishes for package I/Os and circuit board features. Aspects of processability and solder joint reliability were described for the following coatings: baseline hot‐dipped, plated, and plated‐and‐fused 100Sn and Sn‐Pb coatings; Ni/Au; Pd, Ni/Pd, and Ni/Pd/Au finishes; and the recently marketed immersion Ag coatings. The Ni/Au coatings appear to provide the all‐around best options in terms of solderability protection and wire bondability. Nickel/Pd finishes offer a slightly reduced level of performance in these areas which is most likely due to variable Pd surface conditions. It is necessary to minimize dissolved Au or Pd contents in the solder material to prevent solder joint embrittlement. Ancillary aspects that include thickness measurement techniques; the importance of finish compatibility with conformal coatings and conductive adhesives; and the need for alternative finishes for the processing of non‐Pb bearing solders are discussed.

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.

This paper aims to demonstrate the practicability of the liquid metal printer, developed in the authors’ laboratory, in the direct manufacture and assembly of circuit boards at the end customer side using GaIn24.5 alloy as printing ink at room temperature.

A practical procedure for printing a real designed frequency modulation (FM) radio circuit on flexible and transparent substrate using liquid metal printer was established. Necessary electronic components are then assembled on this circuit board. To enhance the mechanical stability of the FM radio circuit board, we further package the circuit board using room temperature vulcanizing silicone rubber. Finally, an efficient way to recycle the liquid metal ink and electronic components is presented at the end of circuit board’s life cycle.

Methods of designing the circuit patterns that are applicable to liquid metal printer are similar to the conventional printed circuit board (PCB) designing strategies. The procedure of applying liquid metal printer for printing the circuits is entirely automatic, cost-effective and highly time-saving, which allows the user to print out desired device in a moment. Through appropriate packaging, the FM radio circuit board can be flexibly used. These PCBs own many outstanding merits including easy modification and stretchability. Nearly all liquid metal ink and components can be recycled.

The present end-customer-oriented liquid metal printing opens the way for large-scale personal electronics manufacture which is expected to initiate many emerging applications in education, design, industry, entertainment and more maker targets.