Copper-filled through-hole electrode of a ZnS window material for sealing a thermal infrared sensor

Takafumi Fukumoto, Naoki Okamoto, Yoshimi Ohta, Yasuhiro Fukuyama, Masaki Hirota, Kazuo Kondo

Research output: Contribution to journalArticlepeer-review


The through-hole electrode for the wafer level package (WLP) was formed with the aim of lowering the cost of infrared sensors. It has been difficult to plate a ZnS substrate for use as the window material of WLPs because of low adhesion. However, through-hole filling was successfully accomplished in this work by applying a newly developed method of direct nonelectrolyte plating. Concretely, a blast cleaning process was performed on a ZnS substrate of 1 mm thickness. Then, a through-hole with both sides tapered was formed with an aspect ratio of 7. A compound process of Cu substitution plating and Ni nonelectrolyte plating was applied to the through-hole, forming a uniform plating film with high adhesion in the hole. Finally, the through-hole was completely filled by Cu electroplating. A He leak test confirmed that the sample had high sealing properties, with a measured leak rate of 1.0 × 10 -10 Pa·m3/sec or less. The results showed that a ZnS substrate can be used effectively for IR window material, making it possible to reduce the cost of infrared cameras.

Original languageEnglish
Pages (from-to)437-442+4
JournalIEEJ Transactions on Sensors and Micromachines
Issue number9
Publication statusPublished - 2010
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering
  • Electrical and Electronic Engineering


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