Technical Library | 2015-02-27 17:06:01.0
The drive towards fine pitch technology also affects the soldering processes. Selective soldering is a reliable soldering process for THT (through hole) connectors and offers a wide process window for designers. THT connectors can be soldered on the top and bottom side of boards, board in board, PCBs to metal shields or housing out of plastic or aluminum are today's state of the art. The materials that are used to make the solder connections require higher temperatures. Due to the introduction of lead-free alloys, the boards need more heat to get the barrels filled with solder. This not only affects the properties of the flux and components, but the operation temperatures of solder machines become higher (...)First the impact of temperature will be discussed for the separate process steps and for machine tooling. In the experimental part measurements are done to verify the accuracy that can be achieved using today's selective soldering machines. Dedicated tooling is designed to achieve special requirements with respect to component position accuracy.
Technical Library | 2017-08-31 13:43:48.0
Wire bonded packages using conventional copper leadframe have been used in industry for quite some time. The growth of portable and wireless products is driving the miniaturization of packages resulting in the development of many types of thin form factor packages and cost effective assembly processes. Proper optimization of wire bond parameters and machine settings are essential for good yields. Wire bond process can generate a variety of defects such as lifted bond, cracked metallization, poor intermetallic etc. NSOP – non-stick on pad is a defect in wire bonding which can affect front end assembly yields. In this condition, the imprint of the bond is left on the bond pad without the wire being attached. NSOP failures are costly as the entire device is rejected if there is one such failure on any bond pad. The paper presents some of the failure modes observed and the efforts to address NSOP reduction
Technical Library | 2017-11-22 12:38:51.0
The use of copper foils laminated to polyimide (PI) as flexible printed circuit board precursor is a standard practice in the PCB industry. We have previously described[1] an approach to very thin copper laminates of coating uniform layers of nano copper inks and converting them into conductive foils via photonic sintering with a multibulb conveyor system, which is consistent with roll-to-roll manufacturing. The copper thickness of these foils can be augmented by electroplating. Very thin copper layers enable etching fine lines in the flexible circuit. These films must adhere tenaciously to the polyimide substrate.In this paper, we investigate the factors which improve and inhibit adhesion. It was found that the ink composition, photonic sintering conditions, substrate pretreatment, and the inclusion of layers (metal and organic) intermediate between the copper and the polyimide are important.
Technical Library | 2018-08-15 17:27:28.0
Smartphones and tablets require very high flexibility and severe bending performance ability of the flexible printed circuits (FPCs) to fit into their thinner and smaller body designs. In these FPCs, the extraordinary highly flexible, treated rolled-annealed (RA) copper foils have recently used instead of regular RA foil and electro deposited foils. It is very important to measure the Young's moduli of these foils predicting the mechanical properties of FPCs such as capabilities of fatigue endurance, folding, and so on. Even though the manufacturers use IPC TM-650 2.4.18.3 test method for measuring Young's modulus of copper foils over many years, where Young's modulus is calculated from the stress–strain (S–S) curve, it is quite difficult to obtain the accurate Young's modulus of metal foils by this test method.
Technical Library | 2023-02-13 19:23:18.0
Spontaneously forming tin whiskers, which emerge unpredictably from pure tin surfaces, have regained prevalence as a topic within the electronics research community. This has resulted from the ROHS-driven conversion to "lead-free" solderable finish processes. Intrinsic stresses (and/or gradients) in plated films are considered to be a primary driving force behind the growth of tin whiskers. This paper compares the formation of tin whiskers on nanocrystalline and conventional polycrystalline copper deposits. Nanocrystalline copper under-metal deposits were investigated, in terms of their ability to mitigate whisker formation, because of their fine grain size and reduced film stress. Pure tin films were deposited using matte and bright electroplating, electroless plating, and electron beam evaporation. The samples were then subjected to thermal cycling conditions in order to expedite whisker growth. The resultant surface morphologies and whisker formations were evaluated.
Technical Library | 2013-12-19 16:57:50.0
With the adoption of RoHS and implementation of Lead Free solders a major concern is how this will impact reliability. Both commercial and military hardware are impacted by this change even though military hardware is considered exempt from the requirements of RoHS. As the supply chain has moved to the new lead free alloys both markets are being forced to understand these impacts and form risk mitigation strategies to deal with the change. This paper documents the effect of mixing Leaded and Lead Free alloys on BGA devices and how this impacts reliability. Three of the most common pitch BGA packages are included in the study to determine if the risk is the same as pitches decrease
Technical Library | 2017-08-10 01:23:22.0
This paper demonstrates the high frequency performance and thermo-mechanical reliability of through vias with 25 μm diameter at 50 μm pitch in 100 μm thin glass substrates. Scaling of through via interconnect diameter and pitch has several electrical performance advantages for high bandwidth 2.5D interposers as well as mm-wave components for 5G modules.
Technical Library | 2020-06-19 19:08:14.0
The designs of electronic devices and systems are being continuously improved by becoming smaller in size and faster in communication speed. The potential risk associated with these specific design improvements will be an increase in power density and, consequently, a greater risk of thermal problems and failures. At the same time, the prevailing use of circuit boards integrated with power devices such as motor controllers and drivers, light-emitting diode (LED) lighting modules, power supplies, and amplifiers, and regulators for TV, etc., drive to the use of a proper thermal management system while designing these kinds of printed circuit board (PCB).
Technical Library | 2022-01-05 23:20:33.0
This study aims to present the characterization of five different types of printed circuit boards (PCBs) for use in future recycling processes. PCBs used: motherboards, lead free motherboards, video cards, memory and printer cards. The comminution of the circuit boards was performed using blade mills and hammer mills with 9mm and 6mm meshes, respectively. Throughout the physical processing, analysis was made with stereoscopic optics to ensure that the correct materials had been released. The pre-magnetic separation parts were given a granulometric classification followed by acid digestion and loss on ignition tests.
Technical Library | 2021-06-07 19:06:32.0
The technological growth of the last decades has brought many improvements in daily life, but also concerns on how to deal with electronic waste. Electrical and electronic equipment waste is the fastest-growing rate in the industrialized world. One of the elements of electronic equipment is the printed circuit board (PCB) and almost every electronic equipment has a PCB inside it. While waste PCB (WPCB) recycling may result in the recovery of potentially precious materials and the reuse of some components, it is a challenging task because its composition diversity requires a cautious pre-processing stage to achieve optimal recycling outcomes. Our research focused on proposing a method to evaluate the economic feasibility of recycling integrated circuits (ICs) from WPCB. The proposed method can help decide whether to dismantle a separate WPCB before the physical or mechanical recycling process and consists of estimating the IC area from a WPCB, calculating the IC's weight using surface density, and estimating how much metal can be recovered by recycling those ICs. To estimate the IC area in a WPCB, we used a state-of-the-art object detection deep learning model (YOLO) and the PCB DSLR image dataset to detect the WPCB's ICs. Regarding IC detection, the best result was obtained with the partitioned analysis of each image through a sliding window, thus creating new images of smaller dimensions, reaching 86.77% mAP. As a final result, we estimate that the Deep PCB Dataset has a total of 1079.18 g of ICs, from which it would be possible to recover at least 909.94 g of metals and silicon elements from all WPCBs' ICs. Since there is a high variability in the compositions of WPCBs, it is possible to calculate the gross income for each WPCB and use it as a decision criterion for the type of pre-processing.
