Application of electrical conductors to an electrically insulating substrate

An electrically insulating substrate having a pattern comprising a pattern of electrical conductors applied on a first side thereof, wherein at least part of the electrical conductors fulfils one or more of the following features:

• (a) a distance between facing edges of adjacent electrical conductors is at least 7.5 μm and is less than 12.5 μm;
• (b) the at least part of the electrical conductors consists of sintered electrically conductive particles and of voids between said sintered particles, the voids being present in at least 1% by area in a cross-section of the electrical conductors;
• and
• (c) the at least part of the electrical conductors includes at least one contact pad that is flat on the first side, the at least one contact pad being capped by a solder bump, and wherein the at least one of the solder bumps capping the at least one of the contact pads have a diameter of at most 50 μm.

An electrically insulating substrate, wherein a pattern of electrical conductors is applied to the substrate by a method comprising:

• a) providing a flexible membrane, wherein a first surface of the membrane has a pattern of grooves formed therein, the pattern corresponding at least partially to a desired pattern of electrical conductors to be applied to the substrate;
• b) loading into the grooves of the first surface of the membrane a composition that includes, as composition components, electrically conductive particles and an adhesive, said loading being performed in one or more filling cycle(s) such that on completion of the loading step the composition substantially fills the grooves, level with the first surface of the membrane, and parts of the first surface between the grooves are substantially devoid of the composition;
• c) contacting the membrane with the substrate, with the first surface of the membrane facing the substrate;
• d) applying pressure to the membrane to cause the composition loaded into the grooves in the first surface of the membrane to adhere to the substrate;
• e) separating the membrane from the substrate to transfer the composition from the grooves in the first surface of the membrane to the substrate;
• and
• f) applying sufficient energy to sinter the electrically conductive particles and to render electrically conductive the pattern of composition transferred to the substrate from the grooves.