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Fig. 10. Timing of the power on/off of the micro-heaters in the mold insert in an injection molding process
Fig. 11. Variations of the temperature of the mold insert heated by various powers during mold-cooling.
Fig. 12. Results of application of heat-generable mold insert presented herein. Molding conditions: PMMA microstructures, barrel temperature 250 °C, mold temperature 120 °C, injection pressure 60 MPa, mold insert started to power on when the mold temperature decreased to 106 °C.
Fig. 13. Defects caused by the excessive heating of the mold insert. (a) collapse of micro-structures， (b) weld-line.
This study investigates the operation window of the injection molding of micro-structures using the developed novel mold insert with the layout of micro-cavities presented in Fig. 12. Fig. 14(a) and (b) show the operation windows in cases in which the micro-structures have a uniform aspect ratio of three and four， respectively. These data reveal that a higher aspect ratio of the micro-structures corresponds to a stricter requirement of the heating conditions of the mold insert. Moreover, mold inserts with higher power-densities must be developed.
Fig. 14. Operation window of the injection molding of PMMA micro-structures with aspect ratios of (a) three， and (b) four using the heat-generable mold insert. Barrel temperature 250 _C, mold temperature 120 _C, injection pressure 60 MPa, mold insert started to power on when the mold temperature decreased to 106 _C.
5. Conclusion
A micro-heater-embedding mold insert for the injection molding of plastic micro-structures with high aspect ratios was presented. The micro heater, created by implanting phosphorus ions into the surface of a silicon mold insert, was demonstrated to exhibit stable physical properties and excellent heating performance, making it very appropriate for continuous injection molding. Using these micro heaters to heat the wall of the mold insert with micro cavities and the nearby plastic for a sufficient duration at a sufficient power in the cooling stage, reduces both the shrinking stress that is produced in the plastic and the de-molding force. Therefore, the de-molding destruction of the injection molded microstructures can be eliminated. Furthermore, the effective moldable area of the injection molding of micro-structures can be expanded.
摘要这项工作提出了用注塑模具热镶件解决脱模中损坏的问题。这个模具镶件是由微加工制成的硅片构成的。微电加热线路嵌入到微模具型腔壁来控制温度分布和注射成型过程中塑料凝固的顺序。这个设计减少了模具中塑料的收缩应力。嵌入到型腔壁的微电加热线路是具有特定电阻的硅基线路，该线路通过精确控制硅型腔表面上的掺杂磷离子。采用磷离子植入技术。本文研究了这种新型镶件的性能。然后，由此开发的模具镶件应用于具有高长宽比的微结构注塑模具。实验结果表明这种电加热线路可以提供稳定的加热功率。这些电加热线路是用来在冷却阶段以在适当的时机和足够的功率加热硅模具镶件的型腔壁和附近的塑料。这样由塑料在微结构模具镶件收缩产生的脱模力会降低。因此，解决注塑模具微结构中脱模破坏问题。可成功地注射成型长宽比大于7的光学微结构。
1 论文网介绍
微结构组件有许多潜在的应用。塑料是非常适合它们制造用的。因此，制造塑料的微结构技术是非常重要的。现在越来越广泛的利用像微结构组件的高质量塑料微结构来编造更多的经济。强烈预期注塑模来支撑大规模稳定和良好的质量的塑料微结构。然而，微结构组件设计的共同特点是列或者行建立在基本比率具有高的长宽比的微结构，因为在产品功能需求和模具镶件制造上的限制，这些微结构不能做草图或做锥角。因此，很容易发生脱模干扰或冷却模具塑料的下滑，导致在微结构注塑塑料零件的表面脱模断裂。所以认为这个问题是引起应力场和建立塑料的收缩比率之间的区别和镶件材料的关键。虽然塑料的收缩率可以受到在冷却期间均匀分布的压力来控制特定塑料模具型腔内的压力，但确保统一的模具塑料的收缩率是很困难的。此外，塑料冷却期间的压力可能会导致不仅产生了产品的残余应力，而且还会对镶件进行破坏。因此，脱模问题与上面描述的微结构的注塑问题不能通过应用塑料冷却时的压力得到解决。