Laser drilling of copper foils for electronics applications

C. J. Moorhouse, Francisco J. Villarreal, Howard J. Baker, Denis R. Hall

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Single pulse drilling of copper foils and copper-coated dielectric circuit board materials, relevant to applications in micro-electronics packaging, has been investigated here using an enhanced peak power CO2-laser. The plasma generated during copper laser ablation, under these conditions, has been found to be self-extinguishing once the copper has been punched through, and does not materially impact the process. The analysis of the undercut formation in the copper coated laminates illustrated a direct link with the energy delivered to the dielectric after the copper has been laser ablated. Holes with zero undercut were obtained by the use of an acousto-optic modulator, used as a pulse shutter, to control the energy delivered to the dielectric. For unmodulated laser pulses, holes with zero undercut were obtained when drilling copper foils 35-µm thick. In general, when drilling copper-coated dielectrics with unmodulated pulses, holes with low undercut were obtained for peak powers < 1.2 kW. However, the stochastic nature of copper drilling dominates the process in this regime. At higher peak powers (up to 1.8 kW), a yield of 100% holes in copper is obtained, but this also results in significant undercut. © 2007 IEEE.

Original languageEnglish
Pages (from-to)254-263
Number of pages10
JournalIEEE Transactions on Components and Packaging Technologies
Volume30
Issue number2
DOIs
Publication statusPublished - Jun 2007

Keywords

  • Carbon dioxide (CO 2 ) lasers
  • Copper
  • Laser drilling
  • Microvia
  • Resin coated copper (RCC)

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