Technical Library | 1999-08-27 09:27:10.0
Conformal coating is a material that is applied to electronic products or assemblies to protect them from solvents, moisture, dust or other contaminants that may cause harm. Coating also prevents dendrite growth, which may result in product failure. This paper will discuss the variables that affect the application of conformal coatings, and review in detail those variables that impact the process of selective coating of printed circuit boards.
Technical Library | 2013-09-25 20:57:24.0
Conformal coating is an enabling process that allows for the ruggedizing of electronic devices and modules. As the process increases the durability of electronics that are subjected to various end-use environmental conditions, it adds value to the product. While it does add value, consumers and manufacturers expect the electronics to work when subjected to dirt, humidity, moisture, corrosive materials, and various other contaminants. This expectation results in a drive to minimize the cost of the process. The lowest cost of ownership for a conformal coating process occurs by utilizing automated selective conformal coating equipment.
Technical Library | 2019-04-07 22:47:46.0
How to protect your PCB from moisture related damage? J-STD-033 put forward stricter regulation on the MSD exposure environment,when the exposure time exceed the tolerated,the moisture will penetrate into electronics,Moreover, the newest RoHS regulation will rise soldering temperature,the sudden high temperature will lead to expansion and cracking on electronic components. In order to decrease the moisture defect on PCB for the manufacturers in China,Climatest Symor® begin to concentrated on electronic dry cabinet R&D since early 1990s,we specialize in handling temperature and humidity for 20 years,and we provide best solution for PCB storage.
Technical Library | 2019-04-11 05:59:57.0
Are your MSD safely stored? As humidity is found to be one of the key reasons for rejected products, many manufacturers are taking measures to control the humidity to increase their production efficiency and save the cost. In the industries of semi-conductor and electronics, the key section in which the rejected products are most probably to be made is that during the heating process of SMT, the IC(e.g.,PBGA,BGA,or TQFD) is likely to crack and thus cause non-effective welding because of the humidity. Climatest Symor® auto dry cabinet is the best solution to avoid the cracking and non#2;effective welding by dehumidifying the surface of your components. The dry unit can be used for 20 years without replacement,and controller is calibration free within 5 years.We attach dry cabinet application with different humidity range,welcome to download.
Technical Library | 2023-09-23 22:29:02.0
Moisture trapped within components and PBs presents a serious problem during the fabrication and assembly process. Too much moisture can lead to board failures when it is turned to steam during the reflow process.
Technical Library | 2020-11-29 22:06:45.0
Plastic laminates are increasingly used as interposers within chip packaging applications. As a component within the package, the laminate is subjected to package moisture sensitivity testing. The moisture requirements of chip packaging laminates are related to ambient moisture absorption and thermal cycling. Printed wiring board (PWB) laminates, however, are gauged on properties relating to wet processes such as resist developing, copper etching, and pumice scrubbing. Consequently, printed wiring board moisture absorption test methods differ from chip packaging test conditions.
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 | 2024-01-08 18:44:00.0
Printed circuit boards, especially multilayer, flexible and rigid-flexible printed circuit boards, are extremely hygroscopic, i.e. they absorb and bind the moisture in the air. A dried polyimide film, for example, will have reached its moisture saturation level again after just a few hours.
Technical Library | 2024-09-02 18:48:58.0
The conversion to higher temperature "Lead Free" assembly reflow conditions has created an increased awareness that entrapped or absorbed moisture is a frequent root cause of thermally induced delamination at assembly reflow. There are two connected failure modes from entrapped moisture; incomplete resin cross-linking resulting in premature resin decomposition and also severe Z axis expansion from "explosive vaporization of the entrapped moisture at elevated temperatures at assembly reflow". Ultimately, both result in delamination failure. Other papers have shown the negative effects of entrapped moisture before lamination including delamination, red color, reduced thermal reliability and increased high speed signal loss. In this paper, various materials were tested for moisture sensitivity during lamination. Tests were performed at varying lamination conditions including a pre-vacuum step and "kiss" step. Pressure and cure temperature parameters were evaluated for minimizing or eliminating the effect of trapped moisture. Also included are the results of inner layer moisture removal baking conditions and their effect on peel strength and thermal reliability.
Technical Library | 2018-09-21 10:12:53.0
Moisture accumulates during storage and industry practice recommends specific levels of baking to avoid delamination. This paper will discuss the use of capacitance measurements to follow the absorption and desorption behaviour of moisture. The PCB design used in this work, focused on the issue of baking out moisture trapped between copper planes. The PCB was designed with different densities of plated through holes and drilled holes in external copper planes, with capacitance sensors located on the inner layers. For trapped volumes between copper planes, the distance between holes proved to be critical in affecting the desorption rate. For fully saturated PCBs, the desorption time at elevated temperatures was observed to be in the order of hundreds of hours. Finite difference diffusion modelling was carried out for moisture desorption behaviour for plated through holes and drilled holes in copper planes. A meshed copper plane was also modelled evaluating its effectiveness for assisting moisture removal and decreasing bake times. Results also showed, that in certain circumstances, regions of the PCB under copper planes initially increase in moisture during baking.
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