A laser selective activation and metallization technology for the manufacturing of ceramic interconnect substrate (CIS)

Ceramic interconnect substrate (CIS) has long been used in markets where performance requirements, such as reliability, thermal conductivity and electrical properties, are critical. Typical manufacturing technologies of CIS are thick film, and high and low temperature co-fired ceramic. A binder was used, which contains silver, gold or other high melting temperature metals as a conducting medium. In addition to these, a number of pure copper metallization (PCM) processes have been developed to deposit copper onto ceramics in order to meet the growing demand for high electrical conductivity, and high-density circuitry. These are known as direct-bonded copper (DBC), and plated and bonded copper (PBC) process. However, the PCM or even thin film technologies still have their limitations when used for fine line fabrication, and/or microvia metallization. A new technology is therefore proposed to selectively activate ceramics using a laser for the fine line fabrication, and microvia activation and metallization. This additive metallization approach is used to produce a conductive line with the line width as small as 50 microns. It also eliminates other additional microvia metallization processes. It is believed that this new technology is able to bridge the technological gap and meet future needs.

R&D methodology

n this proposal, a new technology will be developed to selectively metalize ceramics. First, ceramic surface and microvia holes are activated by laser. Then, copper is deposited selectively by electroless copper plating followed by electroplating. Lastly an annealing process is required to strengthen the bonding between the copper layer and ceramic substrate.
Technologies to be developed in this project:

1. Laser activation and subsequent metallization in Microvia
In microvia activation, the laser intensity insides the microvias is usually lower. Moreover, the hole wall inside microvia is almost parallel to the irradiation direction of the laser beam. These two factors reduce the effectiveness of the activation of the ceramic. Technology to achieve ceramic activation of microvia will be investigated, for instance through controlling the geometry of the microvia.

2. Laser activation for the high quality fine line fabrication
Prima facie, excessive density of laser energy will damage ceramics, while low density may not be able to activate ceramics. The technology is extremely complicated. Thus, the project team needs to focus on the choice of the wavelength of laser. Lasers of different wavelengths react differently with ceramics and yield different results of the degree of activation.
Wavelength is also a determining factor of the physical dimensions or resolution of the activation areas (i.e. conductive lines).

3. Recovery of activated areas
Techniques to recover from activation and return to non-activation status will be developed through chemical and/or physical methods. How the activation status of ceramic varies with the passage of time, and its effect on the quality of conductors will also be investigated. Advantages of the new technology of laser drilling and activation over the existing technologies are that it (i) produces microvia with a smaller diameter, (ii) eliminates certain processes, (iii) produces high density circuitry, (iv) is a fully additive method, (v) is an environmentally friendly process, (vi) allows reworking, and (vii) reduces cost.

The objectives of this project are:

  1. To develop a selective activation and metallization technology for high density and thermal
    conductive ceramic interconnect substrate (CIS).
  2. To develop a technology for drilling and activating microvias simultaneously, for subsequent
    electroless plating


  1. Develop a new pure additive technology for the manufacturing of ceramic interconnect
    substrate (CIS), which include technology to selectively activate surface and microvia by
  2. Investigate the mechanism of laser activation and the effect of processing parameters
    on the quality of conductors and microvias;
  3. Estabish a database of processing parameters for the selective laser activation and
    metallization process.

Project Commencement Date:
December, 2009

Project Completion Date:
December. 20,2010

Principal Investigator:
Dr. Winco K.C. Yung
Tel (852) 2766-6599

Project Team Member:
1. Dr Winco K.C. Yung
2.Prof. T.M. Yue
3. Mr. James Tam
4.Mr. C.P. Lee
5. Ms. Joanne Wong