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Thin Film Metallization Stacks Serve as Reliable Conductors on Ceramic-Based Substrates for Active Implants
IEEE Transactions on Components, Packaging and Manufacturing Technology ( IF 2.2 ) Pub Date : 2020-09-24 , DOI: 10.1109/tcpmt.2020.3026583
Patrick Kiele , Paul Cvancara , Michael Langenmair , Matthias Mueller , Thomas Stieglitz

Substrates and packages of active implantable medical devices are often fabricated from ceramics, such as alumina. Screen-printed PtAu paste is the state-of-the-art metallization for functional structures. Due to solid-state and liquid diffusion of Au during thermal exposure, solder times are limited. Otherwise, metal structures tend to delaminate. Moreover, it was shown that PtAu with solder fails after 37.4 years. We established a thin film metallization on the alumina process to overcome these disadvantages. We used sputtered platinum with an underlying adhesion layer made of tungsten–titanium to increase the adhesion strength of the alumina substrate. We avoided using gold in this work due to its high diffusion tendency. All used materials provided relatively low diffusion properties, which increases independence from joining techniques and mechanical longevity during use. Utilizing the Design of Experiment (DoE) methodology, we derived an optimal Pt thickness of 500 nm with 43 nm of WTi as an adhesion-promoting layer. After accelerated aging at 150 °C, corresponding to 125 years at body temperature (37 °C), the contact pad adhesion strength was 32.75 ± 7.08 MPa. This exceeded the safety limit of 17 MPa by far, set as a recommendation for robust screen-printing metallization processes. Soldering times of up to 120 s did not influence the adhesive strength. The new process reduced the minimum track distance to 50% of screen-printing values and is capable to be transferred into rapid prototyping techniques. It helps to make the assembly process independent of the manufacturing person in order to increase the yield of device fabrication and—most important in implantable device manufacturing—to make it more robust and thereby safer for the patient.

中文翻译:

薄膜金属化叠层作为有源植入物的陶瓷基衬底上的可靠导体

有源可植入医疗设备的基板和包装​​通常由陶瓷制成,例如氧化铝。丝网印刷的PtAu糊是功能结构的最新金属化工艺。由于金在热暴露期间的固态和液态扩散,因此焊接时间受到限制。否则,金属结构容易分层。此外,还表明,使用焊料的PtAu在37.4年后失效。为了克服这些缺点,我们在氧化铝工艺上建立了薄膜金属化工艺。我们使用溅射的铂和一层由钨钛制成的下层粘合层来提高氧化铝基材的粘合强度。由于金的扩散趋势高,我们在这项工作中避免使用金。所有使用过的材料均提供较低的扩散特性,在使用过程中增加了对连接技术的独立性和机械寿命。利用实验设计(DoE)方法,我们得出了43nm的WTi作为粘合促进层的最佳Pt厚度为500nm。在150°C下加速老化后,相当于在人体温度(37°C)下为125年,接触垫的粘附强度为32.75±7.08 MPa。到目前为止,该安全极限已超过17 MPa的安全极限,这是鲁棒丝网印刷金属化工艺的建议。最长120 s的焊接时间不会影响粘合强度。新工艺将最小轨道距离减少到丝网印刷值的50%,并且能够转移到快速成型技术中。
更新日期:2020-11-21
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