Technical Library | 2019-09-27 09:14:41.0
One of the most critical factors in preventing corrosion from occurring in electronics is maintaining the state of cleanliness. This is not an easy feat to achieve. Corrosion is defined as the deterioration of a material or its properties due to a reaction of that material with its chemical environment. [1] So, to prevent corrosion from occurring, either the material or the chemical environment must be adjusted. Adjusting the material usually means application of a protective coating or replacing a more reactive material with a less reactive material. Adjusting the chemical environment usually means removing ionic species through cleaning, and removing moisture, usually with a conformal coating or hermetic package. Ionic species and moisture are problematic because they form an electrolyte which is able to conduct ions and electricity. Any metal that comes into contact with the electrolyte can begin to corrode.
Technical Library | 2019-05-23 10:42:00.0
Why identify flux residues? The primary purpose of flux is to reduce species of metal oxides from solderable surfaces, and to act as a mechanism for lifting and removing debris. If the assembly is not properly cleaned after manufacturing, flux may continue to reduce metals and may eventually corrode the assembly. When the assembly is powered, the metal ions may precipitate along electromagnetic field lines and form dendritic shorts. In addition, the presence of residue can alter the insulation properties of a board, affect the adhesion of the conformal coating, or interfere with the moving parts of the assembly. In radio frequency (RF) applications, flux may change the RF properties on the surface of the printed circuit board (PCB) such as the dielectric strength, surface resistance, and Q-resonance.
Technical Library | 2013-10-22 07:38:42.0
In conformal coating many components and printed circuit board locations must remain uncoated due to the insulating nature of the coating. The purpose of the conformal coating masking materials is to prevent migration of the conformal coatings into components that need to clear and designated keep out areas. This applies to both liquid conformal coating and Parylene processing. Get this basic process wrong and it can be a big problem, leading to the next stage of either repairing the conformal coating leak, stripping the conformal coating off the circuit board, removing a component to replace it or scrapping the board. This paper reviews typical masking application methods in conformal coating and provides advice on minimising problems.
Technical Library | 1999-08-09 11:09:42.0
Organic Solderability Preservatives (OSPs), also known as anti-tarnish, on bare copper printed circuit boards (PCBs) are becoming more prevalent in the electronics industry as the low-cost replacement to Hot Air Solder Leveling (HASL). Introducing the anti-tarnish alternative into the customer sites requires working closely with the coating supplier, assembler, and Original Equipment Manufacturer (OEM) to gain a mutual understanding of respective processing concerns and finished product requirements.
Technical Library | 2021-07-06 21:18:02.0
A new PCB surface finish has been developed that offers outstanding performance and excellent environmental protection. This finish has the potential to replace more common finishes such as ENIG, ImAg, ImSn, ENEPIG, or OSP with a chemically resistant plasma deposited coating. The substitution of the wet processes with this dry plasma process offers significant advantages e.g. lower quantities of chemicals used, environmental benefits and improved operator safety.
Technical Library | 2021-04-08 00:30:49.0
As the electronic industry moves to lead-free assembly and finer-pitch circuits, widely used printed wiring board (PWB) finish, SnPb HASL, has been replaced with lead-free and coplanar PWB finishes such as OSP, ImAg, ENIG, and ImSn. While SnPb HASL offers excellent corrosion protection of the underlying copper due to its thick coating and inherent corrosion resistance, the lead-free board finishes provide reduced corrosion protection to the underlying copper due to their very thin coating. For ImAg, the coating material itself can also corrode in more aggressive environments. This is an issue for products deployed in environments with high levels of sulfur containing pollutants encountered in the current global market. In those corrosive environments, creep corrosion has been observed and led to product failures in very short service life (1-5 years). Creep corrosion failures within one year of product deployment have also been reported. This has prompted an industry-wide effort to understand creep corrosion
Technical Library | 2015-03-04 10:56:26.0
As the proliferation of modern day electronics continues to drive miniaturization and functionality, electronic designers/assemblers face the issue of environmental exposure and uncommon applications never previously contemplated. This reality, coupled with the goal of reducing the environmental and health implications of the production and disposal of these devices, has forced manufacturers to reconsider the materials used in production. Furthermore, the need to increase package density and reduce costs has led to the rapid deployment of leadless packages such as QFN, POP, LGA, and Micro-BGA. In many cases, the manufacturers of these devices will recommend the use of no clean fluxes due to concerns over the ability to consistently remove flux residues from under and around these devices. These concerns, along with the need to implement a tin whisker mitigation strategy and/or increase environmental tolerance, have led to the conundrum of applying conformal coating over no clean residues.
| 1 |
