Oral Sessions


S24: HDI, IC Substrate and FPC Technology

Oct. 28, 2022 10:30 AM - 12:30 PM

Room: 503
Session chair: Chi-Shiung Hsi,National United University/ Irving Lee, Global Manager,UL

RF Circuit challenge of mmWave application
發表編號:S24-1時間:10:30 - 11:00

Invited Speaker

Jennifer Wu, Project Leader Engineer, ICHIA technologies, inc.

The mmWave Commerical promotes the doubling of the data transmission rate to 16Gbs. These performance improvements also affect the development of electronic products toward wireless, systematization, and lightweight. Therefore, the integration of electronic components has higher quality requirements for wireless transmission stability, shortened transmission distance, and reduced energy consumption. Under such performance considerations, RF (radio Frequency) circuit challenge of mmWave will be prersented form the perspectives of wiring, and interlayer connections on the circuit board.

Embedded Trace process by SCHMID
發表編號:S24-2時間:11:00 - 11:15

Laurent Nicolet

ET process by SCHMID has a new process which is capable to process line & space down to 2µm with an embedded trace technology based on the next generation of productions tools.

OBJECTIVE: Demonstrate a process capable to fit the actual and future requirements of Substrates & High-End PCB’s while taking into account the ecological and economical aspect of the process by using a green, Smartfab concept.

METHODS: Major process steps to reach the objective were newly developed. The creation of the trace into a non-fiber material like ABF or Polyimide is done by a Plasma-etching process. The newly developed system combines
a high selective anisotropic etching with none dust produced from the silica particles being present in the material (ABF). The metallization of the created pattern and holes are made by sputtering Ti or TiNx layer following a Cu seed. An optimized Cu plating process is filling traces and vias parallel. The following process is planarized and removing excess Cu from the surface. After that the boards will be ready for the next build up layer.
All major tools used in the ET Process are capable to handle panels up to 620x620mm (24”x4”) in a touch free mode.

RESULTS: Plasma etching of Polyimide is achieve with a speed over 1.5µm and for ABF material of 350nm/min as average etching speed. The depth of traces is 15µm with vias up to 60µm. The metallization of the pattern was made with TiNx following per Cu layer. Cu plating with a uniformity of min 94% for a plating thickness of 26µm simplify the CMP process.

CONCLUSIONS: ET by SCHMID is a process capable to cover the need for the actual and future demand of substrate & High-end PCB’s. The achieved results are showing a high potential for massive improvements in future board design like: Considerable increase in the mass of copper within the PCB, no limitation for the geometry and the quantity of holes and implementing 3D designs. This technology advantages are coming along with a new production tool generation including a smartfab concept to achieve massive saving on energy, chemistry, water and emissions.

Manufacturing Processes of Advancing 3-Dimensional Laser direct Ceramic (LDC) Circuits Boards by Laser Engraving
發表編號:S24-3時間:11:15 - 11:30

Chun Chieh Liao

As the rapid development of technology, the need for the ceramic circuit boards becomes more and more complicated. The traditional direct plating Cu (DPC) ceramics boards, which is patterned by the photo images and electro-plating technique, can only have the pattern on 2-dimensional surface. However, to increase the circuit density on ceramics boards, DPC technique does not meet the requirements of high-density circuits. To reach the high-density circuits on ceramic boards, 3-dimensional ceramic circuit boards are the trend in the future.
Due to the technical limitation of 2-dimensional DPC, it needs to come up with a totally different manufacturing process to achieve the 3-dimensional circuits on ceramic boards. To make the 3-dimesnsional circuits come true, a laser engraving technique which was called laser direct ceramic (LDC) was developed by Tong Hsing Electronic Industries Ltd. The main manufacturing processes of LDC contain five steps. Firstly, ceramic boards were cut by the saw and side wall of ceramic boards could be exposed and be processed. Then, the ceramic boards were sputtered by Ti/Cu seed layers on the top and bottom side. In the meantime, the side wall of ceramic boards was also sputtered by Ti/Cu seed layers. Thirdly, laser machine with 6-axis rotation stage was applied to engrave 3-dimensional pattern on circuit boards. Non-circuit area was engraved by laser and the Ti/Cu seed layers would be evaporated by the energy of laser. Besides, 6-axis rotation stage facilitated to engrave the side wall of ceramic boards and enabled to fulfill 3-dimensional circuits on ceramic boards. After that, the Cu thickness of conductor was increased by electro-less Cu plating or electro-plating Cu. Finally, the surface finish, such as electro-less Ni/Au, was plated on Cu surface to protect the Cu from oxidation and increase the solderability.
In conclusion, the assistance of laser machine with 6-axis rotation stage could make 3-dimensional circuits on ceramic boards and overcame the limitations of traditional 2-dimensional DPC process. The advancing manufacturing processes were proposed in this paper and the new processes could increase the density of ceramic circuits and widen the application of ceramic circuit boards.

Hydrogen Embrittlement Suppressors for Nickel-Free Electroless Copper Baths
發表編號:S24-4時間:11:30 - 11:45

Tobias Bernhard, Stefanie Manuela Bremmert, Sascha Dieter, Laurence John Gregoriades, Edith Steinhäuser

The deposition of a nanovoid-free electroless copper layer is one of the main quality criteria of an electroless copper bath. Without certain additives known to contribute to copper bath stability, copper deposit thickness and color, crystal structure, suppression of nanovoiding, etc., the properties of the obtained copper layer are unpredictable and uncontrolled copper growth can be observed.
Previous investigations have shown that nickel as an additive is one of the main drivers in suppressing hydrogen embrittlement (HE) and thus preventing nanovoiding, while other commonly used organic additives did not show any beneficial impact on suppressing HE.
Despite the advantages of nickel in this regard there are many reasons to substitute nickel as a HE suppression agent. The unavoidable incorporation of nickel in the electroless copper layer can lead to lower conductivity of the electroless copper layer and to lower throwing power in blind micro vias (BMVs). Moreover, a nickel-free electroless copper bath is also preferred in terms of high-quality BMV filling and is less hazardous to health and for the environment.
The report presents the results of a study carried out to investigate the impact of five different additives (A-E) on HE, surface morphology and epitaxy in a wide concentration range for a tartrate-based, nickel-free electroless copper bath. The additives chosen for these investigations belong to different chemical compound classes and can be categorized in organic and inorganic compounds (including transition metal complexes). To study the different effects of the additives on the deposited copper layer focused ion beam (FIB) and scanning electron microscopy (SEM) were utilized for examination.
Additive A shows a complete HE suppression over the entire concentration range studied without negatively affecting other copper deposit properties. For additive B and C, the HE suppression increases with bath concentration while the opposite is observed for additive D. Additive E demonstrates no HE suppression across the concentration range tested.
The results clearly demonstrate that certain additives are capable of completely suppressing the HE phenomenon and of providing thin, epitaxially grown and nanoscopically defect-free electroless copper layers with an optimal surface morphology for the subsequently plated electrolytic copper deposit. Additionally, the avoidance of the encapsulation of hydrogen during the copper deposition process results in a less nanopouros copper deposit, which minimizes the risk for delamination of the deposited copper.
Furthermore, the performance of these additives is comparable over a relatively wide concentration range (additive A: 50-200 ppm), which provides an additional advantage with respect to electroless copper bath handling and dosing. The present results moreover confirm that certain additives can reliably substitute nickel and overcome the HE phenomenon.

Next Generation Pulse Electroplating Copper Metallization for Advanced MLB
發表編號:S24-5時間:11:45 - 12:00

Crystal Zhang

5G network provides high data transmission rate, and will enable internet of things (IoT), autonomous vehicles, Virtual Reality (VR), etc. 5G wireless roll out requires more small-cell base station infrastructure to increase signal coverage. Networking and 5G wireless base station increase demand for advanced high layercount multi-layer boards (MLB) with higher routing density. In order to increase signal routing density, back panel board design trend is higher aspect ratio (AR), for higher board thickness with lower through hole diameter. In recent years, more and more customers are working on through holes with high AR > 16, while conventional AR is lower than 16. Major challenges for copper electroplating on high AR through holes are the balance among high throwing power, good uniformity which includes both the thickness uniformity inside through hole and also the uniformity of isolated features and dense features, together with high mechanical and thermal reliability.
Herein, we report our study on the development of next-generation pulse electroplating copper offering for advanced MLB. Electroplating copper formulation are mainly composed of inorganic additives (cupric ion, acid, and chloride ions), and organic additives (brightener, suppressors). The unique combination of organic additives provides strong suppression effects. In addition, the interaction between additives and pulse waveform has been studied by systematic design of experiments (DOE). Thermodynamics, kinetics, mass transfer, current distribution, and electrochemical crystallization are taken into account during pulse reverse plating, to achieve the balance between through hole throwing power and through hole uniformity. Furthermore, fundamental relationship between crystalline grain structure and plating conditions are investigated toward good mechanical and thermal reliability. The guideline for pulse plating parameters is established. In summary, this paper demonstrates an innovative pulse electroplating copper metallization package with high throwing power, good uniformity, and excellent reliability, for advanced MLB applications.

An Innovative Copper Electroplating Solution for High-Speed HDI Plating
發表編號:S24-6時間:12:00 - 12:15

Shih-Chun Huang

With the emerging development of high-tech applications such as consumer electronics, 5G network, artificial intelligence, and autonomous vehicles, the need of higher quality PCB manufacturing grows accordingly. Among all of PCB applications, high density interconnect (HDI) is one of the essential and fastest growing technology. In order to fulfill various customer’s need, critical challenges arise including higher throughput, wider and deeper via filling, higher aspect ratio through hole plating, and stricter than ever uniformity. To meet the above requirement, innovative plating formulated product is required for industrial development.
Herein, our study focuses on identifying key factors to simultaneously optimize via filling and through-hole plating. By leveraging design of experiment, machine learning, electrochemical experiment and plating verification, we summarized the primary factors and develop an outstanding electrolytic copper additive for HDI application. Proprietary design of organic additives provides excellent via-filling and through-hole throwing power even at 4 ASD. Besides the extraordinary performance, easy bath maintenance with this unconventional electrolytic plating solution is necessary. Moreover, this formulation offers a wide range of operating conditions and stable reliability to reinforce its high-quality manufacturing characteristics. In summary, this paper demonstrates an innovative electroplating solution for HDI applications.

Impact of Additives on the Recrystallisation of Plated Layers
發表編號:S24-7時間:12:15 - 12:30

R. Massey, T. Bernhard, K. Klaeden, S. Zarwell, E. Steinhaeuser, S. Kempa, F. Bruening

The use of electroless and electrolytic Copper plating has been readily adopted by the PCB industry since its onset, so much so that both processes are still considered as being “the best” of the available production techniques. However, as electronics becomes more pivotal in our daily lives, the range of safety and other critical applications is increasing significantly and there is a growing need to push product performance further and to then stabilize that performance at its maximum wherever possible.
While there is an extensive library of publications discussing both the physical testing and performance of various PCB technologies, these have been more recently complimented by disclosures relating to the microstructures found in their Copper layers and how these may also be somewhat influential. One item that has been highlighted within such work is the visibility of any interfaces within a plated structure, and how ideally this would not occur, with no discrete layers being apparent. It is assumed that such epitaxial structures are likely to offer the best opportunity for reliability performance due to a lack of significant macro and micro defects within the plated structure.
Within this paper we compare the influence of plating additives that have been applied to a commercially available electroless copper system and how their use impacts the morphology of the overall final plated structure. Through testing on insulating materials in addition to single and polycrystalline copper substrates, each electroless Cu solution is shown to be influential in suppressing grain growth in certain crystal orientations which can lead to significant physical differences across the final plated interface.
It is interesting to note that while the degree of epitaxy between the substrate Cu and the electroless Cu can be influenced dependent upon the additive utilized, this can occur independently of the impact between the electroless and electrolytic Cu. To wit, an epitaxial interface between the substrate and electroless Cu is not strictly indicative that an epitaxial structure will occur between the electroless and electrolytic Cu.
Through careful selection of the additive packages used within an electroless Cu system, there can be significant control gained over how not only the electroless layer itself crystalizes, but also the response of the subsequent electroplated layer as well. Both of these are understood to have significant impact on the physical and mechanical properties of such an interface, this in turn can be influential in achieving the desired overall properties such as microvia strength or a highly reflective plated surface as is often desirable to flexible PCB production.


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