ENIG, electroless nickel immersion gold is now a well-regarded finish used to enhance and preserve the solder-ability of copper circuits. EPIG, electroless palladium immersion gold, is a new surface finish also for enhancing and preserving solder-ability but with the advantage of eliminating Electroless Nickel from the deposit layer. This feature has become increasingly important with the increasing use of high frequency PWB designs whereby nickel’s magnetic properties are detrimental. We examine these two finishes and their respective soldering characteristics as plated and after steam aging and offer an explanation for the performance deviation.

Comparing the results of steam age test data shows a clear benefit of EPIG over ENIG. After even a short duration exposure to steam, ENIG finishes failed to solder. Much longer steam exposures produced little to no effect on EPIG plated samples. Rapid oxidation of the electroless nickel phosphorous layer when stressed with heat and moisture explains the superior EPIG result.

The ability to demonstrate excellent solder-ability following steam exposure represents increased fabrication reliability under non-ideal storage conditions.

The latest highest reliability requirements demand a high performance electroless nickel and immersion gold (HP ENIG). The new IPC specification 4552A has refocused the industry with reference to nickel corrosion. The interpretation of the existing specification, that judges corrosion on 3 levels, is complex and if misinterpreted can lead to phantom failures. An obvious way to avoid any potential misinterpretation is to eradicate any evidence of corrosion completely. Solderability and environmental corrosion resistance are also highly significant prerequisites when discussing Highest Reliability. These will be evaluated by High Speed Shear testing(HSS)and gas chamber testing respectively.  In addition to the more demanding requirements of the HP ENIG to satisfy High Reliability requirements, the system needs to exhibit good basic layer characteristics. It is also the intention of this paper to evaluate whether there is any ‘value added’ or unintended benefits to a HP ENIG. An example of this would be superior gold distribution and associated gold saving potential. Data generated by Design of Experiment (DOE) will be used to evaluate the impact of electroless nickel variables in combination with traditional and cyanide free immersion gold on recognized quality expectations. The results are expected to be practical and production applicable solution underpinned by solid data and it is hoped that they may dispel myths or misunderstandings within the printed circuit board (PCB)manufacturing environment.

Key words: Highest reliability, Nickel corrosion, Corrosion resistance, Solderability, Black pad

This paper details the realization of a multi-layered, printed, conformable hybrid circuit. The circuit was created using silver(Ag) flake ink as a conductive layer and UV acrylic-based ink as a dielectric layer. Both layers were printed on medical grade thermoplastic polyurethane(TPU) substrates. Traditional surface mount electronic components were attached onto the printed pads to create the multilayered hybrid circuit. Functionality of the hybrid circuit was demonstrated by integrating an embedded microcontroller, a near-field communication(NFC) chip, and a temperature sensing chip. A printed NFC antenna transmitted the measured data from the sensor circuit to a custom mobile device application. The details of the circuit design, fabrication and temperature sensor data are presented in this paper.

Key words: Additive Manufacturing, Component Attachment, Flexible Electronics, Flexible PCB, Flexible Hybrid Electronics, Printed Electronics, Printed NFC antenna, Screen Printing.

As is the case with many other markets where faster, highly capable technologies have resulted in more intelligent processes and products, the medical device sector is also undergoing a “smart” transformation. This has driven the development of medical devices that provide greater access to in-home care and monitoring and faster results for medical professionals, with the overarching benefit of better patient outcomes. Devices applied to the human body that continuously sense and report vital signs in real-time, moisture sensing systems that aid in patient health and comfort optimization, and skin-applied patches with timed drug measurement and release are all smart healthcare realities today. Sensor technologies that bridge the gap between standard, rigid assemblies and more flexible user interfaces are pushing the envelope toward smaller and more convenient form factors, making smart healthcare devices a mainstream reality. This paper will share details about multiple medical sensing applications and the advanced materials and processes used to assemble them for optimal functionality.

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This Presentation discusses Improvements for signal integrity.  Signal integrity is based on the copper surface roughness, the oxides on the copper, and the Dielectric constant of the Dielectric material.  The Dielectric material dielectric constant is effected by the glass weave and the weave pattern.  The weave is also effected by skew.   

This Slide show presents RF Cap Layers to normal FR4 Dielectric materials.  This material can be used in multiple configurations including Single sided, Double sided, and Hybrid.   This material contains different and enhanced Dielectric Frequencies for Radio Frequency PCBs.  

OEMs and CMs designing and building electronic assemblies for high reliability applications are typically faced with a decision to clean or not to clean the assembly. If ionic residues remain on the substrate surface, potential failure mechanisms, including dendritic growth by electrochemical migration reaction and leakage current, may result. These failures have been well documented.

If a decision to clean substrates is made, there are numerous cleaning process options available. For defluxing applications, the most common systems are spray-in-air, employing either batch or inline cleaning equipment and an engineered aqueous based cleaning agent.

Regardless of the type of cleaning process adopted, effective cleaning of post solder residue requires chemical, thermal and mechanical energies. The chemical energy is derived from the engineered cleaning agent; the thermal energy from the increased temperature of the cleaning agent, and the mechanical energy from the pump system employed within the cleaning equipment. The pump system, which includes spray pressure, spray bar configuration and nozzle selection, is optimized for the specific process to create an efficient cleaning system.

As board density has increased and component standoff heights have decreased, cleaning processes are steadily challenged. Over time, cleaning agent formulations have advanced to match new solder paste developments, spray system configurations have improved, and wash temperatures(thermal energy) have been limited to a maximum of 160ºF. In most cases, this is due to thermal limitations of the materials used to build the polymer-based cleaning equipment. Building equipment out of stainless steel is an option, but one that may be cost prohibitive.

Given the maximum allowable wash temperature, difficult cleaning applications are met by increasing the wash exposure time; including reducing the conveyor speed of inline cleaners or extending wash time in batch cleaners. Although this yields effective cleaning results, process productivity may be compromised.

However, high temperature resistant polymer materials, capable of withstanding a 180°F wash temperature, are now available and can be used in cleaning equipment builds. For this study, the authors explored the potential for increasing cleaning process efficiency as a result of an increase in thermal energy due to the use of higher wash temperature. The cleaning equipment selected was an inline cleaner built with high temperature resistant polymer material.

For the analysis, standard substrates were used. These were populated with numerous low standoff chip cap components and soldered with both no-clean tin-lead and lead-free solder pastes. Two aqueous based cleaning agents were selected, and multiple wash temperatures and wash exposure times were evaluated.

Cleanliness assessments were made through visual analysis of under-component inspection, as well as localized extraction and Ion Chromatography in accordance with current IPC standards.

Keywords: Aqueous based cleaning process, PCB defluxing, wash system cleaning parameters, thermal energy, chemical energy, mechanical energy.