Die and Substrate Attachment

Product Name/ Supplier Type Viscosity cps Thixo- tropic Index Shelf Life (-40°C)/ Pot Life (2S C) Cure Schedule % Wt Loss 300°C (TGA) Bond Strength psi MOE MPa psi CTE ppm/°C T, °C Volume Resistivity ohm-cm Thermal Conduc- tivity W/mK Ionic Impur- ities ppm 

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Polyimides for die and substrate attachment and for multilayer circuit insulation where resistance to high temperatures and electrical stability are required. 

Table 5.2 Properties of some die- and substrate-attach adhesives... 

Materials are qualihed by passing a series of tests as severe or more severe than those of the intended application. Generally, accelerated environmental and mechanical tests are specihed and performed on actual or simulated parts representative of the hnal product. Since the parts are subjected to accelerated tests, some of which are destructive, qualihcation parts are seldom deliverable items. Once an adhesive and process have been qualihed, no changes in composition or processes are allowed without requalihcation. Testing at levels above the acceptance tests for an extended duration or number of cycles is necessary. The qualihcation tests for some applications, for example, for die and substrate attachment, have been specihed in NASA and MIL specihcations while those for other applications are being developed by industry and industry associations. 

The first specifications for adhesives were generated by the staff of NASA and the DoD who were prompted by the high reliability that was required of microcircuits used in aerospace programs. These specifications covered primarily die and substrate attachments for hermetically sealed integrated circuits, hybrid microcircuits, and multichip modules. Subsequently, with the increased use of surface-mount adhesives in the assembly of commercial printed-wiring boards and underfills for flip-chip devices, industry associations took the lead in generating the requirements and test methods. 

The test methods covered in this chapter are those most closely related to adhesives for die and substrate attachment, surface-mounting of components, underfill, and optoelectronic assembly. Some tests, such as bleedout and electrical stability, for which there are no standard test methods, are not covered but information for these procedures was already addressed in other portions of this book, for example, in Sections 2.1 and 6.1. 

Table 5.2. Properties of Some Die- and Substrate-Attach Adhesives... 

Table 5.10. NASA Outgassing Data for Some Die- and Substrate-attach...

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