ECRI Microelectronics

LTCC

The LTCC (Low Temperature Co-Fired Ceramic) is a ceramic wiring carrier with a multi-layer structure. A flexible raw material (Green Tape) is used as a base. This unsintered film consists of a mixture of glass, ceramic and organic solvents. The firms Heraeus, DuPont and Ferro for example supply this raw material.

In the manufacturing of a LTCC Ceramic, a corresponding number of layers is started through the cutting of the Green Tapes. Prior to their further processing some materials require an additional Temper-Process at about 120 °C. As a second step the different layers are mechanically processed. This means that the adjustment and plated-through holes (Vias) are punched in the tapes. This is followed by a via-filling pressure and the application of the metallisations, resistors and the other films using a thick film-silk screen process. The usual conductive materials are gold, silver, platinum and palladium alloys. The injecting of the layers and the subsequent sintering at about 850 °C - 900 °C produce the finished multilayers. The sintering causes the LTCC material to shrink by about 12% in the x/y direction and 17% in the z-direction. It is particularly the shrinkage on the x/y-level that adversely affects any adherence to the structural precision. In order to prevent this, non-shrinkage material for the x/y-direction (0.1%) has been developed. This positive effect is achieved through a combination of specially developed tape materials. When deploying this material the increase of the shrinkage in the z-direction (about 45%), especially in the utilisation of holes and cut-out sections, must not be ignored. If this is observed in the construction and processing phases then the 0-shrinkage tape is a step forward in comparison to the traditional LTCC tape material.

Benefits
The possibility of processing the layers individually and in different ways prior to the sintering enables the LTCC to also be used as a packaging construction element. In this way cavities, ducts and other forms can be achieved. This technology enables multilayer structures to be achieved in a simple way with integrated, passive components. LTCC also possesses, apart from the thermal conductivity, the same positive features as thick film circuitry. The leakage of waste heat must be carried out via thermal vias if necessary.

Line-width/space                              75um

Line accuracy                                 ≤±5 um

Camber                                        <3mil/in

Embedded component                            resistors, capacitors, inductors

Number of layers                              30(up)

Tape Choice                                   Dupont 951/943   Ferro A6S/M,  Heraeus

Via Size(Min)                                 100 um

Conductor Material                            Ag, Au, Hybrid system

Cavity                                        Open / Embedded

Via Materail                                  Ag, Au, Transitional material

Thermal Via                                   Optional

Size of substrates                            150mmx150mm  (up)

Inspection of  I/O                            Automatic Test and Vision Inspection

Inspection standard                           MIL-PRF-38534  CLASS H

Annual Total output of LTCC Substrate         5,000,000cm2