Technical Library | 2016-07-21 18:16:06.0
Achieving optimum high-frequency printed-circuit-board (PCB) performance is not simply a matter of specifying the best possible PCB material, but can be significantly impacted by PCB fabrication practices. In addition to appropriate circuit materials and circuit design configurations to meet target performance goals, a number of PCB material-related issues can affect final performance, including the use of soldermask, the PCB copper plating thickness, the conductor trapezoidal effect, and plating finish; understanding the effects of these material issues can help when fabricating high-frequency circuits for the best possible electrical performance.
Technical Library | 2023-05-02 19:06:43.0
As 0402 has become a common package for printed circuit board (PCB) assembly, research and development on mounting 0201 components is emerging as an important topic in the field of surface mount technology for PWB miniaturization. In this study, a test vehicle for 0201 packages was designed to investigate board design and assembly issues. Design of Experiment (DOE) was utilized, using the test vehicle, to explore the influence of key parameters in pad design, printing, pick-andplace, and reflow on the assembly process. These key parameters include printing parameters, mounting height or placement pressure, reflow ramping rate, soak time and peak temperature. The pad designs consist of rectangular pad shape, round pad shape and home-based pad shape. For each pad design, several different aperture openings on the stencil were included. The performance parameters from this experiment include solder paste height, solder paste volume and the number of post-reflow defects. By analyzing the DOE results, optimized pad designs and assembly process parameters were determined.
Technical Library | 2014-08-07 15:13:44.0
Gold embrittlement in SnPb solder is a well-known failure mechanism in electronic assembly. To avoid this issue, prior studies have indicated a maximum gold content of three weight percent. This study attempts to provide similar guidance for Pb-free (SAC305) solder. Standard surface mount devices were assembled with SnPb and SAC305 solder onto printed boards with various thicknesses of gold plating. The gold plating included electroless nickel immersion gold (ENIG) and electrolytic gold of 15, 25, 35, and 50 microinches over nickel. These gold thicknesses resulted in weight percentages between 0.4 to 7.0 weight percent.
Technical Library | 2017-09-07 13:56:11.0
As a surface finish for PCBs, Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) was selected over Electroless Nickel/Immersion Gold (ENIG) for CMOS image sensor applications with both surface mount technology (SMT) and gold ball bonding processes in mind based on the research available on-line. Challenges in the wire bonding process on ENEPIG with regards to bondability and other plating related issues are summarized.
Technical Library | 2006-10-02 14:26:47.0
This paper addresses the assembly and reliability of 0.5 mm pitch leadless Chip Scale Packages (CSP) on .062" immersion Ag plated printed circuit boards (PCB) using Pb-free solder paste. Four different leadless CSP designs were studied and each was evaluated using multiple PCB attachment pad designs.
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.
Technical Library | 2016-05-12 16:29:40.0
Advances in miniaturized electronic devices have led to the evolution of microvias in high density interconnect (HDI) circuit boards from single-level to stacked structures that intersect multiple HDI layers. Stacked microvias are usually filled with electroplated copper. Challenges for fabricating reliable microvias include creating strong interface between the base of the microvia and the target pad, and generating no voids in the electrodeposited copper structures. Interface delamination is the most common microvia failure due to inferior quality of electroless copper, while microvia fatigue life can be reduced by over 90% as a result of large voids, according to the authors’ finite element analysis and fatigue life prediction. This paper addresses the influence of voids on reliability of microvias, as well as the interface delamination issue.
Technical Library | 2016-11-30 15:53:15.0
The use of microvias in Printed Circuit Boards (PCBs) for military hardware is increasing as technology drives us toward smaller pitches and denser circuitry. Along with the changes in technology, the industry has changed and captive manufacturing lines are few and far between. As PCBs get more complicated, the testing we perform to verify the material was manufactured to our requirements before they are used in an assembly needs to be reviewed to ensure that it is sufficient for the technology and meets industry needs to better screen for long-term reliability. The Interconnect Stress Testing (IST) protocol currently used to identify manufacturing issues in plated through holes, blind, or buried vias are not necessarily sufficient to identify problems with microvias. There is a need to review the current IST protocol to determine if it is adequate for finding bad microvias or if there is a more reliable test that will screen out manufacturing inconsistencies. The objective of this research is to analyze a large population of PCB IST coupons to determine if there is a more effective IST test to find less reliable microvias in electrically passing PCB product and to screen for manufacturing deficiencies. The proposed IST test procedure will be supported with visual inspection of corresponding microvia cross sections and Printed Wiring Assembly (PWA) acceptance test results. The proposed screening will be shown to only slightly affect PCB yield while showing a large benefit to screening before PCBs are used in an assembly.
Technical Library | 2020-09-02 22:14:36.0
The demand for miniaturization and higher density electronic products has continued steadily for years, and this trend is expected to continue, according to various semiconductor technology and applications roadmaps. The printed circuit board (PCB) must support this trend as the central interconnection of the system. There are several options for fine line circuitry. A typical fine line circuit PCB product using copper foil technology, such as the modified semi-additive process (mSAP), uses a thin base copper layer made by pre-etching. The ultrathin copper foil process (SAP with ultrathin copper foil) is facing a technology limit for the miniaturization due to copper roughness and thickness control. The SAP process using sputtered copper is a solution, but the sputtering process is expensive and has issues with via plating. SAP using electroless copper deposition is another solution, but the process involved is challenged to achieve adequate adhesion and insulation between fine-pitch circuitries. A novel catalyst system--liquid metal ink (LMI)--has been developed that avoids these concerns and promotes a very controlled copper thickness over the substrate, targeting next generation high density interconnect (HDI) to wafer-level packaging substrates and enabling 5-micron level feature sizes. This novel catalyst has a unique feature, high density, and atomic-level deposition. Whereas conventional tin-palladium catalyst systems provide sporadic coverage over the substrate surface, the deposited catalyst covers the entire substrate surface. As a result, the catalyst enables improved uniformity of the copper deposition starting from the initial stage while providing higher adhesion and higher insulation resistance compared to the traditional catalysts used in SAP processes. This article discusses this new catalyst process, which both proposes a typical SAP process using the new catalyst and demonstrates the reliability improvements through a comparison between a new SAP PCB process and a conventional SAP PCB process.
Technical Library | 2019-10-18 10:37:25.0
It usually does not make any logic to invest in costly fabrication equipment in case you just desire to spin some prototypes and rather outsource your Printed Circuit Board assembly as well as prototype fabrication to a trustworthy vendor. I would provide a few tips as to what to consider when seeking a contract manufacturer. The two most common procedures associated with Printed Circuit Board Assembly are through-hole technology and surface mount technology. Talking about the difference between through-hole technology and surface mount technology. Through-hole elements have metal leads, & these metal leads are supplied through-plated holes inside the circuit board. On the other hand, SMT elements might or might not have leads, nevertheless most significantly, they are developed to be soldered onto the surface of the circuit boards straight on the same side as the element body. A lot of contract manufacturers would provide a quick quote mechanism over their site for the fabrication of circuit boards as well as assembly of prototypes. This would bank your time when comparing various vendors. Ensure that the quote system facilitates you to fill your details, for instance, board material, thickness, copper thickness, milling, etc. in order that you can avail of a precise quote devoid of any surprises afterward. And this is quite necessary. Typically the cost per board would decline as quality upgrades. This is owing to the fairly high setup price of circuit board fabrication over and above component assembly. A few vendors would employ a system where they unite boards from various consumers. This manner the setup price would be circulated among numerous clients. When you fabricate an item, you clearly don’t desire to have to fabricate a big quantity of boards straight away whilst you improve your design. One restriction with small quantity prototypes though is that the option of materials & material thicknesses would be constrained. In case you are employing a particular material then opportunities are there will not be any other clients employing the same material. Additionally, lead time plays a major role in indecisive prices. A longer lead time facilitates the fabricator more liberty in slotting your fabrication. This is basically reflected in cheaper prices that would view in the quote section. Clearly, if you are in a hurry and desire to be moved to the summit of the pile you would require splurging more dollars. Ensure that your contract fabricator would support the file sort for producing which you offer. The most general format for printed circuit board fabrication is the Gerber format nonetheless a few vendors would moreover embrace board files from general printed circuit board software products. A few suppliers also provide in house printed circuit design. Even in case, you create your board yourself, choosing a vendor with design services might prove resourceful in case there is an issue with your files. In this scenario, your vendor could make swift changes that would neglect pricey delays. If you are looking for an Electronic Manufacturing Services (EMS Assembly) provider, then the web is the best to search.
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