Technical Library | 2015-12-31 15:19:28.0
Today's consumer electronic product are characterized by miniatuization, portability and light weight with high performance, especially for 3G mobile products. In the future more fine pitch CSPs (0.4mm) component will be required. However, the product reliability has been a big challenge with the fine pitch CSP. Firstly, the fine pitch CSPs are with smaller solder balls of 0.25mm diameter or even smaller. The small solder ball and pad size do weaken the solder connection and the adhesion of the pad and substrate, thus the pad will peel off easily from the PCB substrate. In addition, miniature solder joint reduce the strength during mechanical vibration, thermal shock, fatigue failure, etc. Secondly, applying sufficient solder paste evenly on the small pad of the CSP is difficult because stencil opening is only 0.25mm or less. This issue can be solved using the high end type of stencil such as Electroforming which will increase the cost.
Technical Library | 2021-08-11 01:00:37.0
Conformal coatings and potting materials continue to create issues for the electronics industry. This webinar will dig deeper into the failure modes of these materials, specifically issues with Coefficient of Thermal Expansion (CTE), delamination, cracking, de-wetting, pinholes/bubbles and orange peel issues with conformal coatings and what mitigation techniques are available. Similarly, this webinar will look at the failure modes of potting materials, (e.g Glass Transition Temperature (Tg), PCB warpage, the effects of improper curing and potential methods for correcting these situations.
Technical Library | 2017-08-24 16:53:20.0
With the rapid development of the information industry, increasing attention is being paid to the dielectric performance of base materials including copper-clad laminates (CCL) and prepregs. In addition to the increasingly high performance requirements of CCL's, the present global attention to less toxic products is leading to an increase in the use of halogen-free flame retardants in electronics. (...) This paper introduces a new phosphonate oligomer which can be used as a reactive flame retardant in epoxy based resin systems. Suitable conditions for the complete reaction between the phosphonate oligomer and epoxy resin are described and the resulting halogen-free laminates with improved properties such as low Df, low coefficient of thermal expansion (CTE), high peel strength, and good toughness are presented.
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 | 2016-01-12 11:03:35.0
With the pitch size of interconnect getting finer and finer, the bonding strength between flexible and rigid (e.g. PCB, ceramic) substrates becomes a serious issue because it is not strong enough to meet the customer’s requirement. Capillary underfill has been used to enhance the bonding strength between flexible and rigid substrates, but the enhancement is very limited, particularly for high temperature application. The bonding strength of underfilled flexible/rigid interconnect is dramatically decreased after being used at 180◦C, and the interconnects are weakened by the internal stress caused by the expansion of underfill at high temperatures. In order to resolve reliability issues of the interconnect between flexible/rigid substrates, solder joint encapsulant was implemented into the thermal compression bonding process, which was used to manufacture the interconnect between flexible/rigid substrates. Compared to the traditional process, the strength of the interconnect was doubled and the reliability was significantly improved in high temperature application.
Technical Library | 2015-02-19 16:54:34.0
Pad cratering is an important failure mode besides crack of solder joint as it’ll pass the regular test but have impact on the long term reliability of the product. A new pin pull test method with solder ball attached and positioning the test board at an angle of 30º is employed to study the strength of pad cratering. This new method clearly reveals the failure mechanism. And a proper way to interpret the finite element analysis (FEA) result is discussed. Impact of pad dimension, width and angle of copper trace on the strength is included. Some findings not included in previous research could help to guide the design for better performance
Technical Library | 2008-03-13 13:02:50.0
Three full-field optical techniques, shadow moiré, fringe projection and digital image correlation (DIC), are used to measure temperature-dependent warpage for a PBGA package and a PCB component land site from room temperature to 250ºC. The results are qualitatively similar, but imaging resolution and noise properties create offsets between coplanarity values. The paper summarizes strengths and weaknesses for each technique.
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 | 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 | 2020-03-26 14:55:29.0
This paper introduces line confocal technology that was recently developed to characterize 3D features of various surface and material types at sub-micron resolution. It enables automatic microtopographic 3D imaging of challenging objects that are difficult or impossible to scan with traditional methods, such as machine vision or laser triangulation.Examples of well-suited applications for line confocal technology include glossy, mirror-like, transparent and multi-layered surfaces made of metals (connector pins, conductor traces, solder bumps etc.), polymers (adhesives, enclosures, coatings, etc.), ceramics (components, substrates, etc.) and glass (display panels, etc.). Line confocal sensors operate at high speed and can be used to scan fast-moving surfaces in real-time as well as stationary product samples in the laboratory. The operational principle of the line confocal method and its strengths and limitations are discussed.Three metrology applications for the technology in electronics product manufacturing are examined: 1. 3D imaging of etched PCBs for micro-etched copper surface roughness and cross-sectional profile and width of etched traces/pads. 2. Thickness, width and surface roughness measurement of conductive ink features and substrates in printed electronics applications. 3. 3D imaging of adhesive dots and lines for shape, dimensions and volume in PCB and product assembly applications.
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