Technical Library | 2019-06-04 10:19:46.0
Interconnection technology relies very heavily on the ability of the conductors on a printed wiring assembly to maintain reliable signal integrity. Harsh environmental factors can precipitate a loss of conductivity due to oxidation and corrosion. Connections are typically soldered or inserted using pressure fitted connectors to obtain enough surface contact to meet the electrical conductivity requirements. In pressure contacts, surface integrity is especially critical where the abrasive effects of retraction and insertion can wear off the metallic finish from the contact area. This can expose the underlying copper or nickel and lead to increased resistance at the contact points. These types of conductors are frequently found in card edge connectors where the terminations are plated with a layer of nickel and gold (frequently referred to as gold fingers). A hard gold is typically used containing very small amounts of nickel and cobalt to increase the wear resistance.
Technical Library | 2020-03-01 23:06:45.0
For though hole soldering, no matter it's wave soldering or selective soldering, the process is same formed by fluxing,preheating,soldering. How these 3 process will change the soldering result? When you face the soldering defects, what could be the reasons caused these and how to debug them? With below information you may get some hints.
Technical Library | 2012-10-23 14:25:38.0
Tin-Silver-Copper alloys are the primary choice for lead-free SMT assembly. Although there are other options available such as alloys containing bismuth or indium and other elements, tin-silver-copper solders, also known as SAC alloys are by far the most popular. They are used by approximately 65% of users, as last surveyed by Soldertec in 2003.
Technical Library | 2019-06-26 23:21:49.0
Copper-filled micro-vias are a key technology in high density interconnect (HDI) designs that have enabled increasing miniaturization and densification of printed circuit boards for the next generation of electronic products. Compared with standard plated through holes (PTHs) copper filled vias provide greater design flexibility, improved signal performance, and can potentially help reduce layer count, thus reducing cost. Considering these advantages, there are strong incentives to optimize the via filling process. This paper presents an innovative DC acid copper via fill formulation, for VCP (Vertical Continues Plating) applications which rapidly fills vias while minimizing surface plating.
Technical Library | 2013-06-20 14:33:12.0
With today's consumer technologies driving the need for denser and more compact devices, the assembly process for surface mounted devices has becoming increasingly more difficult. With the mixture of components requiring a broader range of print deposition volume, various techniques are in use in an attempt to ensure consistent and appropriate paste volume is achieved. Some of these techniques include step etching a stencil locally on a targeted device, promoting electroformed smooth wall nickel stencils, through to laser cutting newer grade stencil materials. This paper focuses on the relevant attributes that affect the properties of solder paste release and introduces the effects of surface free energy with respect to key elements that make up the stencil printing process.
Technical Library | 2020-01-09 00:00:30.0
PCBs have a wide range of applications in electronics where they are used for electric signal transfer. For a multilayer build-up, thin copper foils are alternated with epoxy-based prepregs and laminated to each other. Adhesion between copper and epoxy composites is achieved by technologies based on mechanical interlocking or chemical bonding, however for future development, the understanding of failure mechanisms between these materials is of high importance. In literature, various interfacial failures are reported which lead to adhesion loss between copper and epoxy resins. This review aims to give an overview on common coupling technologies and possible failure mechanisms. The information reviewed can in turn lead to the development of new strategies, enhancing the adhesion strength of copper/epoxy joints and, therefore, establishing a basis for future PCB manufacturing.
Technical Library | 2014-12-04 18:27:40.0
A review on applications of metal-based inkjet inks for printed electronics with a particular focus on inks containing metal nanoparticles, complexes and metallo-organic compounds. The review describes the preparation of such inks and obtaining conductive patterns by using various sintering methods: thermal, photonic, microwave, plasma, electrical, and chemically triggered. Various applications of metal-based inkjet inks (metallization of solar cell, RFID antennas, OLEDs, thin film transistors, electroluminescence devices) are reviewed.
Technical Library | 2017-11-15 22:49:14.0
While a significant level of voiding can be tolerated in solder joints where electrical conductivity is the main requirement, voiding at any level severely compromises thermal conductivity. For example, in LED lighting modules effective conduction of heat through the 1st level die attach to the substrate and then through the 2nd level attach to the heat sink is critical to performance so that voiding in the solder joints at both levels must be minimized. (...) In this paper, the authors will review the factors that influence the incidence of voids in small and large area solder joints that simulate, respectively, the 1st and 2nd level joints in LED modules and discuss mitigation strategies appropriate to each level. They will also report the results of a study on the effect on the incidence of voids of flux medium formulation and the optimization of the thermal profile to ensure that most of the volatiles are released early in the reflow process.
Technical Library | 2019-05-01 23:18:27.0
Moisture can accelerate various failure mechanisms in printed circuit board assemblies. Moisture can be initially present in the epoxy glass prepreg, absorbed during the wet processes in printed circuit board manufacturing, or diffuse into the printed circuit board during storage. Moisture can reside in the resin, resin/glass interfaces, and micro-cracks or voids due to defects. Higher reflow temperatures associated with lead-free processing increase the vapor pressure, which can lead to higher amounts of moisture uptake compared to eutectic tin-lead reflow processes. In addition to cohesive or adhesive failures within the printed circuit board that lead to cracking and delamination, moisture can also lead to the creation of low impedance paths due to metal migration, interfacial degradation resulting in conductive filament formation, and changes in dimensional stability. Studies have shown that moisture can also reduce the glass-transition temperature and increase the dielectric constant, leading to a reduction in circuit switching speeds and an increase in propagation delay times. This paper provides an overview of printed circuit board fabrication, followed by a brief discussion of moisture diffusion processes, governing models, and dependent variables. We then present guidelines for printed circuit board handling and storage during various stages of production and fabrication so as to mitigate moisture-induced failures.
Technical Library | 2015-09-17 17:36:56.0
RoHS legislated restrictions on the materials used in electronics manufacture have imparted significant challenges on the electronics industry since their introduction in 2006. The greatest impacts have been felt by the mandated elimination of lead from electronic solder followed by the demand for the elimination of haloids from flame retardants used in traditional PCB laminates. In the years which have followed the electronics industry has been beset with a host of new challenges in its effort to comply. Failure mechanisms, both new and old, have surfaced which demand solution and the industry suppliers and manufacturing technologists have worked diligently to remedy those vexing faults through the development of a wide range of new materials and equipment for both board manufacture and assembly, along with modifications to the processes used in the manufacture and assembly of printed circuit boards.