以光固化製備三維導電結構之研究

Abstract

3D列印能夠快速製造複雜的三維結構，而在眾多3D列印技術中，光固化技術具有最高的解析度以及最好的表面品質。前人在文獻中提出了利用光固化技術製備三維導電結構，但導電度都相當低(約0.1 S/cm)。為了改善導電度的問題，我們在本研究中使用高導電性的銀銅金屬。然而，銀銅金屬高密度的特性導致其在高分子樹脂中快速沉降，亦造成列印過程中銀銅金屬的不均勻分散。除此之外，為了達到高導電度，必須使用高濃度的銀銅金屬，但如此高的金屬含量會屏蔽掉UV光，使固化速度下降。這些限制使得我們難以利用光固化樹脂製備三維導電結構。 本研究提出了一種新的光固化導電樹脂的組成。首先，將銀銅金屬分散於由奈米碳管形成的網路結構中，藉此減緩銀銅金屬的沉降速度。藉由最佳化奈米碳管的含量來兼具樹脂的流動性以及穩定性，讓3D列印機得以將導電樹脂製備成三維導電結構。同時也計算及最佳化其他會影響導電度或模量的樹脂組成或固化參數。在印製出高品質的多層電路板後，能夠在其中觀察到89.68度的錐角以及0.964的正反面銅墊面積比。總而言之，本研究提出了一種新的調製導電樹脂的方法，並且為光固化技術方面拓展了一條嶄新的道路。

The 3D printing nature provides fast fabrication of complicated 3D structure. Among all 3D printing methods, stereolithography method has the highest resolution and surface quality. Previous studies have shown the 3D conductive structures produced with fairly low conductivity (~ 0.1 S/cm) by stereolithography method. To address this conductivity issue, highly conductive silver-coated copper (AgCu) is adopted here. However, the large density of AgCu leads to fast sedimentation in polymeric resin solution, and also non-uniform AgCu distribution in the printing process. In addition, high AgCu concentrations are needed for high conductivity, but the high metal content shields UV light and therefore leads to low curing rate. These limitations make photo-curable resin unable to be printed into 3D conductive structures. In this study, a new photo-curable conductive resin is formulated. The AgCu is first suspended with the help of carbon nanotubes (CNT), which form a supporting network to decrease the AgCu settling speed. The content of CNT is then optimized to give both fluidity and suspension stability so that the resin composite can be printed into 3D conductive structure. Moreover, effects of various formulation parameters on the conductivity or modulus will be also evaluated and optimized. Multi-layer circuit boards are built with great quality. Taper angle of 89.68 degree is observed and the size ratio of top pad to down pad is 0.964. In summary, this study provides a new approach for conductive resin formulation and pave the way for more stereolithography innovations.