Paste adhesives thermally conductive

Nonconductive or electrically insulative adhesives are used where electrical shorting may be a problem or where electrical isolation is required. Nonconductive adhesives are available in either paste or film form and are generally filled with silica or alumina to provide optimum flow properties for dispensing and to improve their thermal conductivities. 

DM 3030, Silver/glass die attach paste. Thermally Conductive Adhesives Selection Guide. Diemat, a Namics Co, www.diemat.com 2003. 

Once the epoxy bumps have been formed, the wafer is thinned from the backside, the devices are singulated, and their edges beveled at 45° to expose gold pads at the periphery of die. The chips are then stacked and bonded with thermally conductive, electrically insulative epoxy (Figure 5.16). Paste adhesives are cost effective and can be dispensed with existing epoxy dispensing equipment. However, with... 

To assure optimum conductance, the adhesive must be applied as thinly and uniformly as possible. To control the thicknesses bond lines, thermally conductive paste adhesives have been formulated with collapsible spacers. The spacers are reported to control bond line thickness to 30 pm. Bond line thicknesses and uniformity may also be achieved by using film or preform tape adhesives and controlling the applied pressure and heat during cure. 

Chem. Descrip. Boron nitride CAS 10043-11-5 EINECS/ELINCS 233-136-6 Uses Lubricant, filler for elec, insulating/thermally conductive materials, polymer matrixes, adhesives, pastes, potting compds., EP lubricants, refractories, refractory coatings, mold/die release, metal/ceramic and ceramic/matrix composites... 

A typical thermally conductive epoxy system used as an adhesive, as well as for other purposes, has a thermal conductivity of 0.0026 cal/cm/sec/°C and a volume resistivity of 1.5 x 10 ohm.cm (1.5 x 10 ohm.m). Fillers include alumina (aluminum oxide), beryllia (beryllium oxide), other unspecified inorganic oxides, boron nitride, and silica. Boron nitride is an excellent choice as a thermally conductive filler except that its content reaches a maximum at about 40% by weight in epoxy resins. The resultant products are always thixotropic pastes. BerylUa powder has excellent thermal conductivity by itself, but when mixed with a resin binder its conductivity drops drastically. It is also highly toxic and high in cost. Alumina is a commonly used filler to impart thermal conductivity in resins. ... 

Table 3 Composition and properties of electrically and thermally conductive adhesive pastes based on polyimide oligomer 99 (IP 605).

Table 12.3 Composition and Properties of Electrically and Thermally Conductive Adhesive Pastes Based on Polyimide Oligomer 99 (IP 605)...

Adhesives used in connector applications include Loctite s 3887 isotropic epoxy conductive grade. This two part product comes as a thick paste which is cured by exposure to heat and which is designed for enhanced adhesion to gold plated devices in electronic interconnect applications. The product formulation is reported to absorb stress associated with extreme thermal mismatch between dissimilar substrates. 

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