Abstract A method of forming circuit interconnections between adjacent circuits of a multilayer circuit structure is described in which corresponding sets of solder protrusions carried on conductive tracks of adjacent circuits are separated by a layer of uncured, heat-curable insulating material having a transient state, in which the material becomes deformable, between the uncured and the cured states. The layer is heated and the circuits are urged towards one another during the transient, deformable state of the material so that the protrusions pierce the layer, corresponding protrusions contacting one another and the heat subsequently causing the material to become cured. Finally, the contacting protrusions are fused together.
A method as claimed in claim 1, in which the layer is heat curable and the curing includes a first stage of raising the temperature of the layer to the first level which will cause the layer to undergo its curing process but will not cause the terminal protrusions to fuse, and a second stage in which, after the layer is fully cured, the temperature of the protrusions is raised to a level sufficient to fuse the protrusions.
Claim 2
Dependent Claim
22 words
A method as claimed in claim 2, and including the step of forming said insulating layer from a phenolic-butynol dry adhesive film.
Claim 3
Dependent Claim
32 words
A method as claimed in claim 3, in which during the first stage the temperature is raised to approximately 160*C, and during the second stage the temperature is raised to approximately 250*C.
Claim 4
Dependent Claim
27 words
A method as claimed in claim 1 in which said terminal protrusions are formed by applying solder to the substrate at each of the said desired positions.
Claim 5
Dependent Claim
37 words
A method as claimed in claim 1, in which said terminal protrusions are formed by applying a copper element to the substrate at each of the said desired positions and then coating the copper element with solder.