Non-Toxic Stabilization for Mixed Reaction Gold

In this paper, the performance of a complete halogen-free (HF) board assembled with five ball grid array components using daisy chains on an 8-layer high density interconnection printed circuit board (PCB) was examined using bending tests. The solder joint was composed of the SAC405 solder ball melted with the SAC105 solder paste on the Cu pad surface of either organic solderable preservative (OSP) or electroless nickel immersion gold (ENIG), and was tested to examine the extent of intermetallic compound (IMC) formed. A board-level cyclic bending test was executed to the as-reflowed assemblies according to the JESD22-B113 standard to evaluate the reliability of various surface finished HF PCB assemblies under a recommended load condition. By Weibull analyzes the characteristic lives of the assemblies were 99098 and 130290 cycles on OSP soldering system and ENIG system respectively, indicating that the ENIG had a higher bending fatigue endurance as compared to the OSP. The dominant failure mode was the fracture of Cu trace within the micro-via caused by the crack of the resin coated copper layer. At the interface of the solder joint, the IMC formed on both OSP and ENIG was with various Ni contents of 3.9 and 20.1 at%, and different thicknesses of 5.6 and 1.1 , respectively. Numerical simulations showed that both composition and thickness of IMC influenced the stress concentrations and characteristic life of the HF test vehicle as they could slightly increase localized solder joint rigidity and result in more serious pull and drag behaviors at the corner joint. Although the on the ENIG was stiffer than that on the OSP, the thicker IMC layer instead increased the stress on the OSP system due to size effect, and resulted in a lower characteristic life.

Corrosion on automobile printed circuit broad

This study reports a number of experiments that were designed to characterize aluminum bond pad surfaces prior to electroless nickel immersion gold (ENIG). In the ENIG process, aluminum bond pads need special treatment to achieve successful nickel deposition and provide reliable interconnection of under bump metallurgy in advanced packaging. During this treatment process, the aluminum pad was cleaned, activated and then coated with a layer of zinc. Systematic study was carried out to determine the best parameters, through multiple and various exposure times of the zincation process and zincation solution concentration effect on the Ni/Au surface roughness and aluminum dissolution rate on the bond pad during multiple zincation process. The ball shear strength was evaluated between eutectic 37Pb/63Sn solder ball and under bump metallurgy (UBM) interfaces across multiple zincation process. Scanning Electron Microscope (SEM), Energy Dispersive X-Ray (EDX), Atomic Force Microscopy (AFM), Focused Ion Beam (FIB) and ball shear tester were used as analytical tools. The results suggest that the multiple zincation process consistently produces a smoother surface of ENIG UBM and consequently provides a better shear strength.

The iNEMI technical subcommittee on creep corrosion has developed a flowers-of-sulfur (FOS) based qualification test for creep corrosion on printed-circuit boards (PCBs). In phase 1 of the project, the performances of FOS chambers of two designs were evaluated by measuring the corrosion rates of copper and silver foils. In the 1 st and 2 nd test runs of phase 2 of the project, PCBs with immersion silver (ImAg) and lead-free hot-air-surface-level (HASL) finishes soldered with rosin and organic acid fluxes were tested. The ImAg PCBs soldered with organic acid flux suffered the most creep corrosion in agreement with the generally expected field experience. There were fewer instances of creep corrosion on ImAg PCBs soldered with rosin flux and on Pb-free HASL PCBs. The 3 rd test of phase 2 discovered that contaminating the test PCBs with ammonium salts contributed to more creep corrosion but made the test less discriminatory in that even test PCBs with HASL finish soldered with rosin flux suffered creep corrosion. The results of the 4 th through 6 th test runs of phase 2 of the iNEMI project are reported in this paper. The test condition changes included the introduction of chlorine using household Clorox and of pre-baking the test PCBs. The test chambers were maintained at 50°C. In the 4 th and 5 th test runs the relative humidity was maintained at 81% using KCl saturated salt solution. Pre-baking the test PCBs at 100°C for one day under nitrogen gas cover was found to be necessary to generate creep corrosion. The creep corrosion on ImAg PCBs was in general more than that on HASL and OSP PCBs. Creep corrosion was most severe on ENIG (electroless nickel immersion gold) PCBs, independent of the flux used. The 6 th test run studied the effect of relative humidity on creep corrosion. A surprising result was that the iNEMI prepared ENIG PCBs suffered creep corrosion even at the relatively low relative humidity of 60%. The test is now sufficiently developed for consideration by the industry as a qualification test for creep corrosion on PCBs.

355 nm UV laser patterning and post-processing of FR4 PCB for fine pitch components integration

Board level drop testing is an effective method to characterize the solder joint reliability performance of miniature handheld products. In this study, drop test of printed circuit boards (PCB) with four-screw support condition was conducted for a 15 mm /spl times/ 15 mm fine-pitch ball grid array (FBGA) package assembly with solder ball compositions of 36Pb-62Sn-2Ag and Sn-4Ag-0.5Cu on PCB surface finishes of organic solderability preservative, electroless nickel immersion gold and immersion tin. The results revealed a strong influence of different intermetallic compound formation on soldered assemblies drop durability. The lead-based solder supersedes the lead-free composition regardless of the types of surface finish. Joints on organic solderability preservative were found to be strongest for each solder type. Other factors affecting drop reliability such as component location on the board and thermal aging effects are reported.

Board-level drop testing is an effective method to characterize the solder joint reliability performance of miniature handheld products. In this study, drop test of printed circuit boards (PCBs) with a four-screw support condition was conducted for a 15 mm times 15 mm fine-pitch ball grid array (FBGA) package assembly with solder ball compositions of 36Pb-62Sn-2Ag and Sn-4Ag-0.5Cu on printed circuit board (PCB) surface finishes of organic solderability preservative, electroless nickel immersion gold, and immersion tin. Finite element modeling of the FBGA assembly was performed to study the stress-strain behavior of the solder joints during drop test. The drop test results revealed a strong influence of different intermetallic compound formation on soldered assemblies drop durability. The lead-based solder supersedes the lead-free composition regardless of the types of surface finish. Joints on organic solderability preservative were found to be strongest for each solder type. Other factors affecting drop reliability such as component location on the board and thermal cycling aging effects are reported. Finite element modeling results showed that a solder joint is more prone to failure on the PCB side, and the predicted solder joint stresses are location dependent. Predicted failure sites based on simulation results are consistent with experimental observations.

Tin-Silver-Copper (SnAgCu) lead-free solder on Electroless Nickel Immersion Gold (ENiG) and Immersion Tin (ImSn) surface finish printed circuit board was subjected to blast test. A variation of intermetallic compounds (IMC) layer, hardness and reduced modulus of soldered sample exposed to blast test were intensively investigated using optical microscope and nanoindentation machine. Formation of IMCs due to reaction between solder and substrate during blast test provided deleterious effect of metallurgical bond strength and reliability on the solder joint. Microstructural analysis was evaluated via Infinite Focused Microscope (IFM). The findings of these studies indicate that best surface finished for blast test performance was not necessarily the best surface finish for optimum reliability. ENiG and ImSn surface finish can be advantage or a disadvantage depending on the application, package and reliability requirements. As a result, most component assemblers are using ENiG and ImSn in order to improve solderability as well as the wettability between solder and the substrate and to meet various package requirements.

Electroless Nickel Immersion Gold (ENIG) is one of the important final finish techniques that is used in the printed circuit board industry. Despite its relatively expensive cost compared to other final finishing processes such as OSP and immersion Tin etc., ENIG has many advantages. The low reactivity of Au can protect the underlying Ni and Cu surfaces from oxidation and keeps the board suitable for long storage time. It provides excellent surface planarity suitable for soldering, especially for tiny parts such as BGA and FlipChip, and the surface remains solderable even after multiple reflow cycles. It is useful for contact surfaces such as membrane switches and contact points and may also be used for wire bonding. The Immersion Gold (IG) bath provides the protective Au layer after the Electroless Ni (EN) process following the below equation: 2Au+ + Ni _ 2Au + Ni <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> . As an electrochemical process, the deposition rate (or Au thickness per unit of time) is highly dependent on the redox potential of Au <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and electropotential of the Ni surface. The former can be considered as a fixed value in a Au plating solution while the latter will vary depending on the design of boards (pad size, connection of pad to the inner-layer Cu, etc.). The differences of surface potential, or so-called galvanic effect, makes the deposition of Au non-uniform, which may influence the properties of the board in many aspects. For example, chromatic aberration of the Au surface appears and some of the extremely thick Au pads may appear as red color; solderability may become uneven across all pads; and Au may be wasted due to the poor gold thickness distribution. More seriously, the galvanic effect may cause Au skip-plating, or black Ni because of Ni over-dissolution on specific pads, resulting in the solderability problem. Our new immersion gold technology can effectively reduce the galvanic effect by introducing a new chemical system. The electropotential differences were minimized among pads with various surface areas or connected to different inner-layer copper areas thus providing a uniform gold deposition. Meanwhile, the plated Au thickness can be steadily increased from less than 1 microinch to 3 microinches and metallic lustre of the Au surface remained normal, from the pale yellow of thinner Au to the lemon yellow of thicker Au. Ni corrosion resistance remained good for a range of Au thickness from 1 microinch to 3 microinches. Modified HNO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> porosity test yielded good results. Solderability test using SAC305 solder showed good reliability after 0×, 3× reflow and baking (150 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C, 4 hours) conditions in ball shear and ball pull test.

Paper deals with results of solderability testing of Printed Circuit Boards (PCBs). For measurement was used one of the solderability evaluation methods known as the wetting balance test. The wetting balance test measures the wetting forces imposed by the molten solder on the test surface as it is dipped into and held in the solder bath as a function of time. Paper will present the comparison of results of printed circuit board solderability test with preheating in agreement with IPC/EIA J-STD-003A, with IEC 60068-2-54 and with hot air double-sided preheating. This comparison will be also made for several lead-free surface finish types. It was tested printed circuit board coupons with surface finishing of galvanic tin, immersion tin, ENIG (electroless nickel immersion gold), OSP (organic solderability preservative) and pure copper.

The use of surfactants and supercritical CO2 assisted processes in the electroless nickel plating of printed circuit board with blind via

Continuous glucose monitoring is a pressing need in the management of diabetes mellitus. In this study, we report the development of an innovative electrochemical enzymatic biosensor engineered by immobilizing glucose oxidase on a cystamine-modified ENIG (electroless nickel immersion gold) electrode on a printed circuit board and decorating it with spherical Prussian Blue nanostructures with diameters of 30-90 nm. This multilayered architecture demonstrated enhanced electron transfer efficiency and stable chronoamperometric responses across varying glucose concentrations. The biosensor exhibited immediate, reproducible current changes upon glucose addition, with superior sensitivity at an optimized Prussian Blue concentration of 5 mM. Stability tests conducted over 8 days confirmed consistent performance, but highlighted the need for postanalysis regeneration steps. Furthermore, real-time monitoring experiments in a simulated interstitial fluid environment demonstrated the sensor's ability to maintain functionality over extended immersion periods, delivering rapid, distinct electrochemical signals in response to glucose fluctuations. These results underscore the potential of this biosensor design for future applications in minimally invasive, continuous glucose monitoring systems.

The long term reliability of lead-free Sn 96.5 Ag 3.0 Cu 0.5 (SAC305) has been assessed under accelerated temperature cycling (ATC) conditions. Test vehicles consisted of printed circuit boards (PCBs) with three different Pb-free surface finishes Organic Solderability Preservative (OSP), Immersion Silver (IAg) and Electroless Nickel Immersion Gold (ENIG). These boards were connected to the ball grid arrays (BGAs) and 2512 chip resistors by a lead free solder joint. The components were subsequently thermally cycled from 0°C to 100°C with 30 minute dwell times at the upper and lower temperature limits. They were monitored for electrical failures which were defined by a resistance reading of &gt;1000. The life times of the BGAs and chips were predicted using 2-parameter and 3-parameter Weibull analysis as a function of board finish and alloy. Life times were substantially influenced by board finish therefore optical and scanning electron microscopy (SEM) were performed on as-received and post temperature cycling samples in order to establish their effect on failure mechanisms and on microstructural evolution as a result of thermal cycling.

Printed circuit board integrated wearable ion-selective electrode with potential treatment for highly repeatable sweat monitoring

To miniaturize the conventional air gap waveguide (GW), a substrate integrated gap waveguide (SIGW) is proposed. Moreover, SIGW makes up the defects in the microstrip-ridge air GW, such as inconstant gap height, holes in strip, as well as strip electroless nickel immersion gold (ENIG) coating. To verify the proposed SIGW, a prototype was designed and manufactured using the multi-layer printed circuit board (PCB) technology. It contains a very simple transition between SIGW and microstrip lines for measurements. Further, the experimental results show that the measured performance agrees well with the simulated.