This study is part of a series of papers on mitigation of voids in solder joints. Voiding is an ongoing concern for printed circuit board assembly (PCBA) manufacturers. As bottom terminated components (BTCs) become increasingly popular, the potential for voiding in solder joints has increased. Voiding limits are often imposed on PCBA manufacturers. These voiding limits lead manufacturers to find ways to mitigate voiding.
There are two major mechanisms for void formation. The first mechanism is gas entrapment in the solder joint. Gasses come from volatile materials in the flux, air gaps in the solder paste print, and from the PCB and components. The second mechanism for void formation is incomplete wetting or spread of the solder. When the solder alloy does not completely wet both the PCB pads and component leads, gaps remain in the solder joint.
This study is a continuation of work on voiding with respect to solder alloy and stencil design for quad-flat no-lead (QFN) components. The solder alloys tested include Sn63/Pb37, SAC305, SnBiCuNi, SnAgBiCu, and Sn37BiX. A water-soluble Pb-free solder paste flux and SAC305 reflow profile were used. The stencil design was varied on the QFN thermal pads to determine how gap size affects wetting of the solder alloy. Wetting behavior and gas entrapment were correlated to voiding for each solder alloy. The data for both parts of the study was summarized, and recommendations given to help “Fill the Void.”

ETS (Embedded Trace Substrate) is one of advanced substrate design that enable to make fine width and space. The Cu trace open defect on ETS layer (L01) revealed by this OSP micro etching is non-detectable defect mode because OS test (Open-Short test) to detect this kind of defects is done before OSP process. The reason of OS test prior to OSP process is to prevent damage on Cu surface coated with OSP caused by OS test pin mark. OS test can be done after OSP process to detect this defect. But there was no specific study or approach regarding solder joint quality with OS test pin mark. TCNCP (Thermal Compression bonding with Non Conductive Paste) solder joint quality associated with OS test pin mark on ETS layer coated with OSP is investigated. This study demonstrates that Cu trace open on ETS layer generated by OSP micro etching can be detected by OS test prior to OSP process, and it is revealed that TCNCP solder joint quality can be worse due to increased NCP (Non Conductive Paste) entrapment as the number of OS test retrial times are increased.

The explosion of data in the 4th Industrial Revolution has increased the importance of high-performance computing (HPC). HPC requires high-density I/O count to be formed in small area, but the low yield limitations of manufacturing large-area chips for this purpose have led to the development of chiplet and interposer. Interposer are used to bridge the difference in circuit width between chips and PCBs. Use of organic interposers is a recent technology trend, which combine the high resolution of Si interposer with the low-cost production of PKG (Package) board. Due to the inter-chip connectivity and performance of top-mounted HBM, Logic, etc., organic interposer can also embed Si, IPD, DTC, etc. dies inside, which can increase the performance of the entire system and gain a cost competitive edge. [1-3] However, the cavity and asymmetrical structure for this purpose causes warpage, so interposer manufacturers are focusing on warpage control to ensure reliability. This paper focuses on a methodology for improving the warpage of organic interposer. We identify the effect of circuit asymmetry caused by embedded chips and cavities on warpage, and forcibly impose structural asymmetry, such as changing the mechanical properties of the insulation layer and the thickness arrangement of each layer, including the core, and propose warpage improvement ideas based on them. Our findings provide material and structural design guidelines for interposer fabrication and can be utilized to improve the performance and reliability of advanced packaging applications

Sn-58Bi lead-free low-temperature solder (LTS) is regarded as a candidate for low-temperature assembly of electronics components, but its usage field is limited in Surface Mount Technology (SMT). The present study reports on the technical issues of a recent conventional wave soldering system when it is combined with Sn-58Bi LTS, the suspected reasons for each defect, and modifications to adapt modern production work. The critical defects on the printed circuit board (PCB) were severe contamination of dross, which was caused by viscosity thickening of flux in a low-temperature environment. In addition, the spongy dross that accumulates in the tank not only worsens the pollution, but also impairs the economic efficiency of the material. A redesigned nozzle and the addition of a dross removal function were introduced to improve system feasibility. Cooling equipment and flux were also optimized to stabilize finish quality. By selecting an effective organic acid based on energy calculations and modifying the viscosity at high temperatures, a new flux was developed to eliminate the fillet volume shortage caused by the inherent oxidation and low surface tension of LTS. A predictable defect in the rework process is lift-off when Sn-based solder is added, and in order to avoid this, it is necessary to maintain a high bismuth density in LTS supply. LTS wave soldering has shown promising results over Sn-3Ag-0.5Cu (SAC305) in terms of TCT evaluation and reduction of energy consumption and CO2 emissions. Through comprehensive research, the LTS wave soldering system demonstrated its industrial feasibility.

Deep microporous crab legs and abnormal crystallization of coating are common defects in the electroplating process, which have a significant impact on the reliability of PCB products. In this paper, the finite element analysis method is used to numerically calculate the flow state of the plating solution on the PCB surface and in the hole during the jet process. The velocity distribution of the plating solution in the blind hole with different aspect ratio (AR) was obtained. In addition, the influence of electroplating parameters such as current density, waveform time ratio, positive and negative current ratio on the effect of deep microporous electroplating is studied through experiments. The results show that when electroplating and jet flow parameters are synergistic, these defects can be effectively improved.

Chiplet technology is rapidly applied to the latest devices as high performance of semiconductor devices is required. As chiplet becomes vibrant, IC packaging substrates become bigger and more layered. High current density is required due to these changes of IC packaging substrates.
Wiring design also becomes complicated as the technology is matured. Especially IC packaging substrates have various wiring in a board such as L/S 8/8 μm below dense line pattern and 20 μm isolated line pattern.
Dense line pattern mentioned above is likely to have thinner plating deposition as electrical current flow is dispersed. On the other hand, isolated line pattern is likely to have thicker plating deposition as current flow is concentrated. Therefore, it leads to plating thickness unevenness.
Current density gap between isolated and dense fine line pattern is relieved by increasing electric charge of Nitrogen type organic compound (Leveler), and it leads to superior plating thickness uniformity.

Applications for dielectric materials are becoming ever more demanding and complex, requiring careful planning & material selection by original equipment manufacturer (OEM) designers that wish to build reliable products. Some applications may be purely digital and benefit from a very low dielectric constant (e.g., Dk < 3.0) while others, such as radio frequency (RF) applications with high power requirements may benefit from having a higher Dk (e.g., >5). An emerging trend now is the rise of hybrid product designs that combine both traditionally digital and RF materials, especially in the case of high-density interconnects (HDIs). In this paper, methods for tuning the material Dk by careful selection of specialty resins and filler material combinations will be reviewed. The use of mineral fillers for achieving high Dk is a well-established practice that comes with certain considerations such as safety, drilling compatibility, and effects on signal integrity. By contrast, the use of hollow fillers to achieve low Dk is a more recent development that comes with similar considerations, along with chemical composition and morphology concerns. Each of these concerns must be addressed by the product designer, and careful, reliable measurement of the Dk is critical to validating product performance.

The growing demand for high-performance and compact electronic devices has led to increasing power densities, resulting in thermal challenges that impact packaging, performance, and reliability. This paper describes controlled viscosity molding (CVM) applied heat transfer material to a printed circuit board assembly compared to heat removal of mainstream methods. Passive thermal management is chosen as a basis for comparison but is not limited in design. This paper does not include active or advanced heat transfer methods, such as heat pipes or advanced thermally conductive materials, as early developments remain focused on consumer grade technologies and serve as a more acceptable form for comparison. It is focused on demonstrating suitability as a heat transfer method while preserving electronic functionality and in some cases increasing system performance while preserving damaging temperature limits. Thermal simulations have been performed in parallel to confirm and build confidence in some baseline tests. Thermal simulations can serve as a proxy for functional prototypes saving time and money while mitigating risk to product development. A commercially available Battery Management System (BMS) is used for the basis of comparison because of its availability, cost, and use of common heat generating electrical components. CVM with heat transfer material on a printed circuit board can replace aluminum heat sinks as a passive heat control method.

Today, the evaluation of circuit board assembly materials extends beyond their technical performance. An increasingly important aspect of this evaluation centers on whether the material helps improve the sustainability of the organization. The assessment of assembly materials for circuit boards now encompasses their environmental impact across raw material sourcing, industrial processing, and end-of-life management, as well as their societal implications for the well-being of manufacturing personnel and end-users, all while considering cost-effectiveness. It is the responsibility of material suppliers to deliver innovative solutions that meet these multifaceted criteria. This paper delves into circuit board assembly materials, spanning from low temperature solders and reinforcement polymers to bio-based encapsulation resins, with a primary focus on sustainability.

Polycarbonate/Acrylonitrile butadiene styrene (PC/ABS) blends are widely used engineering thermoplastic materials in electronic applications for TV frames, computer peripherals, phone housings/cases, device enclosures, etc. While PC/ABS blends are generally tough, certain chemical environments can contribute to catastrophic brittle failure at relatively low stress levels. Global concern on e-waste and growing emphasis on sustainability lead to increasing adoption of Post-Consumer Recycled (PCR) plastic resins in the production of consumer electronics, which has also increased the demand for PCR PC/ABS materials for the electronics industry. However, high loadings of recycled content may trade off mechanical integrity of the materials, making the blends more susceptible to Environmental Stress Cracking (ESC) and fatigue related part failures. Novel PCR PC/ABS blends using tailored polycarbonate siloxane copolymer chemistry show significantly improved stress cracking resistance. They support very high loading of recycled components (60-80% PCR PC, and up to 86% renewable content) while maintaining excellent chemical resistance to consumer chemicals, such as sunscreen, skin oils, and insect repellent. They also deliver high impact resistance across a wide temperature range (down to -30 oC) that traditional flame retardant (FR) PC/ABS materials do not possess. Furthermore, the new PCR PC/ABS blends offer comparable FR performance, heat resistance, modulus/strength, flow characteristics, and color-ability to traditional blends. This paper will also review various ESC testing methods and compare new PCR PC/ABS blends with other PC based blends.