超声时效技术在微注塑模具制作中的应用

Application of ultrasonic stress relief technology to microinjection mold fabrication

针对金属微注塑模具UV-LIGA制作过程中由于SU-8胶内应力过大而引起的胶膜破裂、变形甚至脱落等问题,提出将超声时效技术应用于微注塑模具的制作工艺。首先,利用紫外光刻工艺制备了电铸胶膜,在显影前使用自制的超声时效装置对胶膜进行超声处理。然后,采用无背板生长方法在38CrNiMnMo模具钢基底上直接进行镍金属的电铸生长,讨论并解决了工艺过程中遇到的SU-8胶浮胶变形、非圆形基片的匀胶、胶膜中的气泡以及微电铸层结合不牢等问题。最后,制作出微通道宽度和高度分别为80μm和35μm的微注塑模具。实验结果表明,超声时效技术的使用避免了由于SU-8胶内应力过大引起的破裂、变形甚至从基底脱落等缺陷,增强了UV-LIGA技术制作微注塑模具的能力,提高了制作微注塑模具的成功率。

In the UV-LIGA fabrication process of a microinjection metal mold, the large internal stress of a SU-8 layer can result in SU-8 mould defects such as micro cracks, distortion or even exfoliation. In order to avoid these defects, the ultrasonic stress relief technology was introduced into the microinjection process. First, the SU-8 mould was obtained by coating, soft baking, ultraviolet exposure and post-exposure baking,and it was treated by the ultrasonic stress relief equipment before developing. Then the backless plate growing method was adopted to directly fabricate the nickel microlectroforming pattern on a 38CrNiMnMo mould steel substrate and the SU-8 layer defects emerged in the process such as the distortion and exfoliation in the SU-8 spin coating on a non-circular substrate, theair bubbles in photoresist layer and the adhesion of plating layer with the substrate were eliminated or improved. Finally, the microinjection mold with a channel width of 80 μm and a height of 35μm was fabricated. The results show that by using the ultrasonic stress relief technology, the SU-8 mould defects caused by large internal stress in SU-8 layer are overcome, the capacity of manufacturing microinjection mold via UV-LIGA technology is enhanced, and the success rate of microinjection mold fabrication is greatly improved.