Assembly Bonded at the Ends: Could Thinner and Longer Legs Result in a Lower Thermal Stress in a Thermoelectric Module Design?
Assembly Bonded at the Ends: Could Thinner and Longer Legs Result in a Lower Thermal Stress in a Thermoelectric Module Design?
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DOI：
10.1115/1.4006597
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发表时间：
2012-11
期刊：
影响因子：
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通讯作者：
E. Suhir;A. Shakouri
中科院分区：
文献类型：
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作者：
E. Suhir;A. Shakouri
建立了电子组件的热应力分析(数学)模型，该组件由端部粘结的相同元件组成，并承受不同的温度。该模型用于评估粘合区(腿)的大小(x方向上的尺寸)和柔度对最大界面剪应力的影响，该最大界面剪应力被认为是导致组件机械稳定性的原因。给出了简化的双腿铋碲合金(BTA)热电模块设计的数值算例。已经确定，较薄(在水平方向上的尺寸)和较长(在垂直方向上的尺寸)的粘结(腿)可以导致界面应力的相当大的缓解。在对具有两个周边1 mm厚(x方向尺寸)支腿的10 mm长(x方向尺寸)的TEM组件进行的数值实例中，当粘结占据组件组件之间的整个界面时，预测的最大界面剪应力仅为相应的均匀结合组件中最大应力的约40%。也已经确定，如果采用粗短腿，最大界面剪应力可能与均匀结合组件中的应力相差不大，因此，就组件的物理设计和稳定性而言，没有必要使用均匀结合或多腿系统。然而，为了使设备具有令人满意的功能(热电)性能，可能需要应用这样的系统。在任何情况下，确保装配中有足够的结合强度是非常重要的。如果考虑非常细长的腿以获得较低的应力，则应通过实验确定(比方说，通过剪切试验)界面的最小可接受尺寸(实际尺寸)，以使该强度不会受到影响。另一方面，由于具有细长支腿的组件的应力水平较低，其界面强度的保证比具有均匀粘结的组件或具有僵硬的粗短支腿的组件更小。基于所建议的预测模型，所获得的结果可特别用于考虑以多个大(粗和长)腿为特征的现有瞬变电磁设计的替代方案。在我们的新设计中，可以使用更少的小(细和短)腿，从而将瞬变电磁的尺寸和厚度减小到可接受的应力水平。[DOI：10.1115/1.4006597]
An analytical (mathematical) thermal stress model has been developed for an electronic assembly comprised of identical components bonded at their end portions and subjected to different temperatures. The model is used to assess the effect of the size (dimension in the x-direction) and compliance of the bonded regions (legs) on the maximum interfacial shearing stress that is supposedly responsible for the mechanical robustness of the assembly. The numerical example is carried out for a simplified two-legged Bismuth-Telluride-Alloy (BTA)-based thermoelectric module (TEM) design. It has been determined that thinner (dimension in the horizontal, x-direction) and longer (dimension in the vertical, y-direction) bonds (legs) could result in a considerable relief in the interfacial stress. In the numerical example carried out for a 10 mm long (dimension in the x-direction) TEM assembly with two peripheral 1 mm thick (dimension in the x-direction) legs, the predicted maximum interfacial shearing stress is only about 40% of the maximum stress in the corresponding homogeneously bonded assembly, when the bond occupies the entire interface between the assembly components. It has been determined also that if thickand-short legs are employed, the maximum interfacial shearing stress might not be very much different from the stress in a homogeneously bonded assembly, so that there is no need, as far as physical design and robustness of the assembly is concerned, to use a homogeneous bond or a multileg system. The application of such a system might be needed, however, for the satisfactory functional (thermo-electrical) performance of the device. In any event, it is imperative that sufficient bonding strength is assured in the assembly. If very thin legs are considered for lower stresses, the minimum acceptable size (real estate) of the interfaces (in the horizontal plane) should be experimentally determined (say, by shear-off testing) so that this strength is not compromised. On the other hand, owing to a lower stress level in an assembly with thin-and-long legs, assurance of its interfacial strength is less of a challenge than for an assembly with a homogeneous bond or with stiff thick-and-short legs. The obtained results could be used particularly for considering, based on the suggested predictive model, an alternative to the existing TEM designs, which are characterized by multiple big (thick-and-long) legs. In our novel design, fewer small (thin-and-short) legs could be employed, so that the size and thickness of the TEM is reduced for the acceptable stress level. [DOI: 10.1115/1.4006597]