Technical Library | 2021-01-28 01:55:00.0
Printed circuit board surface finishes are a topic of constant discussion as environmental influences, such as the Restriction of Hazardous Substances (RoHS) Directive or technology challenges, such as flip chip and 01005 passive components, initiate technology changes. These factors drive the need for greater control of processing characteristics like coplanarity and solderability, which influence the selection of surface finishes and impact costs as well as process robustness and integrity. The ideal printed circuit board finish would have good solderability, long shelf life, ease of fabrication/processing, robust environmental performance and provide dual soldering/wirebonding capabilities; unfortunately no single industry surface finish possesses all of these traits. The selection of a printed circuit board surface finish is ultimately a series of compromises for a given application.
Technical Library | 2019-09-24 15:41:53.0
This paper focuses on three different coating material groups which were formulated to operate under high thermal stress and are applied at printed circuit board manufacturing level. While used for principally different applications, these coatings have in common that they can be key to a successful thermal management concept especially in e-mobility and lighting applications. The coatings consist of: Specialty (green transparent) liquid photoimageable solder masks (LPiSM) compatible with long-term thermal storage/stress in excess of 150°C. Combined with the appropriate high-temperature base material, and along with a suitable copper pre-treatment, these solder resists are capable of fulfilling higher thermal demands. In this context, long-term storage tests as well as temperature cycling tests were conducted. Moreover, the effect of various Cu pre-treatment methods on the adhesion of the solder masks was examined following 150, 175 and 200°C ageing processes. For this purpose, test panels were conditioned for 2000 hours at the respective temperatures and were submitted to a cross-cut test every 500 h. Within this test set-up, it was found that a multi-level chemical pre-treatment gives significantly better adhesion results, in particular at 175°C and 200°C, compared with a pre-treatment by brush or pumice brush. Also, breakdown voltage as well as tracking resistance were investigated. For an application in LED technology, the light reflectivity and white colour stability of the printed circuit board are of major importance, especially when high-power LEDs are used which can generate larger amounts of heat. For this reason, a very high coverage power and an intense white colour with high reflectivity values are essential for white solder masks. These "ultra-white" and largely non-yellowing LPiSM need to be able to withstand specific thermal loads, especially in combination with high-power LED lighting applications. The topic of thermal performance of coatings for electronics will also be discussed in view of printed heatsink paste (HSP) and thermal interface paste (TIP) coatings which are used for a growing number of applications. They are processed at the printed circuit board manufacturing level for thermal-coupling and heat-spreading purposes in various thermal management-sensitive fields, especially in the automotive and LED lighting industries. Besides giving an overview of the principle functionality, it will be discussed what makes these ceramic-filled epoxy- or silicone-based materials special compared to using "thermal greases" and "thermal pads" for heat dissipation purposes.
Technical Library | 2013-03-07 18:25:36.0
The market for high-layer-count printed circuit boards (PCB) containing blind and buried vias was once relatively small, and focused on specialized applications in the military and high end computing. The demand for these types of PCBs today is being driven by an increasing number of commercial applications in the telecommunications and semiconductor test market segments. These applications typically require high-aspect-ratio plated-through-holes (PTHs) and blind and buried vias in order to meet the applications interconnect density requirements. Blind and buried vias and high aspect ratio PTHs continue to present manufacturing challenges and frequently are the limiting features to achieving high fabrication yield... First published in the 2012 IPC APEX EXPO technical conference proceedings
Technical Library | 2013-08-01 13:17:44.0
Electronic industry uses a number of metallic materials in various forms. Also new materials and technology are introduced all the time for increased performance. In recent years, corrosion of electronic systems has been a significant issue. Multiplicity of materials used is one reason limiting the corrosion reliability. However, the reduced spacing between components on a printed circuit board (PCB) due to miniaturization of device is another factor that has made easy for interaction of components in corrosive environments. Presently the knowledge on corrosion issues of electronics is very limited. This paper reviews briefly the materials used in electronic systems, factors influencing corrosion, types of corrosion observed in electronics, and testing methods.
Technical Library | 2015-12-23 16:57:27.0
The onset of copper barrel cracks is typically induced by the presence of manufacturing defects. In the absence of discernible manufacturing defects, the causes of copper barrel cracks in printed circuit board (PCB) plated through holes is not well understood. Accordingly, there is a need to determine what affects the onset of barrel cracks and then control those causes to mitigate their initiation.The objective of this research is to conduct a design of experiment (DOE) to determine if there is a relationship between PCB fabrication processes and the prevalence of fine barrel cracks. The test vehicle used will be a 16-layer epoxy-based PCB that has two different sized plated through holes as well as buried vias.
Technical Library | 2021-10-12 18:01:49.0
The existence of counterfeit products, e.g., integrated circuits (ICs) and printed circuit boards (PCBs), in the modern semiconductor supply chain has seriously jeopardized the security and reliability of electronic systems, and has also caused the loss of suppliers' profit and reputation. Most of existing research papers prevent or detect counterfeit IC and PCB substrate separately, without testing the PCB as a whole, and often require the assistance of external equipment. In this article, a novel ring oscillator- based PCB authentication (ROPA) methodology to detect counterfeit PCB through supply chain is proposed, which ...
Technical Library | 2018-07-11 22:46:13.0
For a demanding automotive electronics assembly, a highly thermal fatigue resistant solder alloy is required, which makes the lead-free Sn-Ag-Cu type solder alloy unusable. Sn-Ag-Bi-In solder alloy is considered as a high reliability solder alloy due to significant improvement in thermal fatigue resistance as compared to a standard Sn-Ag-Cu alloy. The alloy has not only good thermal fatigue properties but it also has superior ductility and tensile strength by appropriate addition of In; however, initial results indicated a sub-par performance in joint reliability when it is soldered on a printed circuit board (PCB) with Electroless Nickel Immersion Gold (ENIG) surface finish. Numerous experiments were performed to find out appropriate alloying element which would help improve the performance on ENIG PCBs. Sn-Ag-Bi-In solder alloys with and without Cu additions were prepared and then tests were carried out to see the performance in a thermal fatigue test and a drop resistance test.to investigate the impact of Cu addition towards the improvement of joint reliability on ENIG finish PCB. Also, the mechanism of such improvement is documented.
Technical Library | 2020-05-28 02:19:28.0
Properly functioning printed circuit boards are essential for both manufacturers of electronic devices and also the developers if the overall intent is for the electronic device to function at high capacity. From designing the schematics of the printed circuit boards to testing the products, there is no process of PCB manufacturing and/or assembly that can be taken for granted. While it's true that you can attempt this process on your own, especially if you are in possession of a large scale manufacturing facility, here are a few reasons why it would be a better option to opt for a professional company for PCB manufacturing and assembly. 1. Variety A professional printed circuit boards manufacturing company will be able to offer you a huge variety. You will be able to choose from rigid, flexible, or rigid-flex. What's more, the PCBs will be customized as per the need of the application. 2. Quality Professional and good printed circuit board manufacturing and assembling companies might cost you just a little bit extra but they also guarantee to produce the best results and offer very high quality products. In the end, it is quality that will make the difference between mediocre and a high functioning PCB. 3. Cost Efficiency Since you don't have to waste time or resources on buying equipment to produce the best PCBs or hiring staff to oversee the process, you can actually end up saving money. You can even save on PCB assembly cost by hiring this job out. All you have to do is to negotiate the quote and sit back, relax, and wait for the PCBs to be delivered to you. 4. Eliminate Design Flaws Design engineers hired by PCB manufacturing and assembling companies use the best graphic software to develop and test the schematics of PCBs. This increases the chances of eliminating flaws in the printed circuit boards during the initial design phase. 5. Multilayer PCB Manufacturing and Assembly The process of manufacturing and assembling multilayer PCBs is as intricate as it sounds. All processes of manufacturing and assembling multilayer PCBs require the best machines and trained technicians to pass the quality and functionality tests. Manufacturing and assembling multilayer printed circuit boards yourself is going to cost you a lot. Even the smallest of mistakes during the manufacturing and assembling process might render the entire PCB entirely useless. 6. Save Time PCBs are just a single part of the electronic device. To complete the device, many more pieces would be needed. The manufacturers of the electronic device can hire out the job of manufacturing or assembling the PCBs, which will mean they will have one less chore to do. This, in turn, will save you a lot of time which could be spent on elevating the quality of the product. 7. Experience Experience makes all the difference. It is what makes the name of any company reliable in the market. Long experience of manufacturing and assembling printed circuit boards makes the company well versed in the process and it also makes it an expert to identify design, manufacturing, assembling, and testing needs of certain applications We, at Asia Pacific Circuits, offer these benefits and so much more. For quick turn PCB assembly, PCB manufacturing and PCB designing, you can contact us anytime.
Technical Library | 2015-07-01 16:51:43.0
Aerospace and military companies continue to exercise RoHS exemptions and to intensively research the long term attachment reliability of RoHS compliant solders. Their products require higher vibration, drop/shock performance, and combined-environment reliability than the conventional SAC305 alloy provides. The NASA-DoD Lead-Free Electronics Project confirmed that pad cratering is one of the dominant failure modes that occur in various board level reliability tests, especially under dynamic loading. One possible route to improvement of the mechanical and thermo-mechanical properties of solder joints is the use of Pb-free solders with lower process temperatures. Lower temperatures help reduce the possibility of damaging the boards and components, and also may allow for the use of lower Tg board materials which are less prone to pad cratering defects. There are several Sn-Ag-Bi and Sn-Ag-Cu-Bi alloys which melt about 10°C lower than SAC305. The bismuth in these solder compositions not only reduces the melting temperature, but also improves thermo-mechanical behavior. An additional benefit of using Bi-containing solder alloys is the possibility to reduce the propensity to whisker growth
Technical Library | 2016-05-19 16:03:37.0
As consumers become more reliant on their handheld electronic devices and take them into new environments, devices are increasingly exposed to situations that can cause failure. In response, the electronics industry is making these devices more resistant to environmental exposures. Printed circuit board assemblies, handheld devices and wearables can benefit from a protective conformal coating to minimize device failures by providing a barrier to environmental exposure and contamination. Traditional conformal coatings can be applied very thick and often require thermal or UV curing steps that add extra cost and processing time compared to alternative technologies. These coatings, due to their thickness, commonly require time and effort to mask connectors in order to permit electrical conductivity. Ultra-thin fluorochemical coatings, however, can provide excellent protection, are thin enough to not necessarily require component masking and do not necessarily require curing. In this work, ultra-thin fluoropolymer coatings were tested by internal and industry approved test methods, such as IEC (ingress protection), IPC (conformal coating qualification), and ASTM (flowers-of-sulfur exposure), to determine whether this level of protection and process ease was possible.
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