FUNCTIONALITY TESTS AND QUALITY OF ALICE SSD MODULES R. Vierimaa1,M. Oinonen1, S. Nikkinen1, Z. Radivojevic1,2, H. Seppänen1, and the ALICE SSD Collaboration 1
Helsinki Institute of Physics, P.O.B 64, FIN-00014 UNIVERSITY OF HELSINKI, Finland Nokia Research Center, P.O.Box 407, FIN-00045, HELSINKI, Finland email
[email protected] 2
An ALICE Silicon Strip Detector (SSD) module contains 2 x 6 128-channel front-end chips bonded on two hybrids and those connected on a silicon strip sensor [1]. In total, 1698 such modules are being used for tracking highly energetic particles in the ALICE experiment at CERN. After assembly, the final functionality tests are performed with a setup engineered in the Utrecht University and established in the assembly sites. Module production is shared between Helsinki, Strasbourg and Trieste and total production in January 2006 was 1257 for which 838 was tested and xxx in Helsinki. During a test, the digital parts of the front-end chips are tested first. This allows also for checking possible connection problems of the flexible hybrid tails. Noise levels of the individual channels are measured without bias voltage applied. The module – the individual channels behaving like diodes – are then forward biased up to 5 V and then reverse biased up to 94 V with a noise measurement at each step. This allows for determining the complete IV curve of the module. N–side noise integral is used for depletion voltage determination. Predefined test limits are used to obtain the module quality as Q = 100 – defected channels. An acceptable module possesses a quality of Q > 70. The Al-Al spTAB technology used in the project has never before being used in such a large-scale detector assembly project. Therefore, the assembly project at different sites has been characterized as convolution of multiple “learning curves”, one experienced in each assembly step. This contribution discusses the resulting SSD module quality which has eventually reached close to 100% in Helsinki. [1] M.Oinonen et al., Proceedings of the conference LECC’05, 12-16 September, 2005, Heidelberg, Germany, ISBN 92-9083-262-2, ISSN 0007-8328, CERN-2005-011, CERN, Geneva, 2005.
