US 6,284,086 B1Granted

Apparatus and method for attaching a microelectronic device to a carrier using a photo initiated anisotropic conductive adhesive

AssigneeThree-Five Systems, Inc.

InventorsTerri Cardellino, Michael Richards

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Abstract

A very low stress attachment method for attaching a microelectronic device to a flexible substrate comprises use of a photo initiated anisotropic conductive adhesive, preferably an infrared photo initiated anisotropic paste, which can be applied to the bonding terminals of a microelectronic device. The flex circuit is then aligned with the corresponding pads on the device. The flex circuit is then biased against the microelectronic device and the infrared photo initiated anisotropic adhesive is exposed to infrared light by means of a dual purpose light guide that presses against the back side of the polyimide flex circuit and simultaneously receives and guides light energy from an Nd: YAG laser to the back side of the polyimide flex circuit. Light energy from the laser passes through the polyimide substrate and between the circuit tracks of the flex circuit to excite the photo initiator of the photo initiated ACA material, thereby causing it to cure. Preferably the ACA material is a dual cure epoxy such that the photo initiator is required only to begin the polymerization process and a secondary (low-temperature thermal or preferably cationic) polymerization carries the cure through the bulk of the material.

Claims10

Dependent claims

A method of attaching a microelectronic device to a carrier, the carrier comprising a flexible substrate having a top side and a bottom side, the top side of the carrier including a plurality of conductive traces disposed thereon, the flexible substrate being substantially transparent to light energy having wavelengths within a first wavelength range, the microelectronic device having a plurality of conductive pads on a surface thereof, the method comprising:

providing a plurality of conductive bonding pads on the top side of the carrier, selected ones of the conductive bonding pads being electrically interconnected to selected ones of the plurality of conductive traces disposed on the top side of the carrier;
applying an anisotropic conductive adhesive between the conductive pads of the microelectronic device and the conductive bonding pads on the carrier, the anisotropic conductive adhesive comprising a photo initiated adhesive;
applying pressure to seat the microelectronic device on the carrier and to complete the electrical connections between the conductive pads and the bonding pads through the anisotropic conductive adhesive;
and
exposing the back side of the carrier to a source of light comprising a wavelength within the first wavelength range such that the light waves within the first wavelength range are substantially transmitted through the flexible substrate to initiate the curing process of the anisotropic conductive adhesive, wherein light from the light source is guided to the back side of the carrier by means of a light guide, said light guide being substantially transparent to light energy having wavelengths within the first wavelength range.

2 more elements

providing a plurality of conductive bonding pads on the top side of the carrier, selected ones of the conductive bonding pads being electrically interconnected to selected ones of the plurality of conductive traces disposed on the top side of the carrier;
applying an anisotropic conductive adhesive between the conductive pads of the semiconductor device and the conductive bonding pads on the carrier, the anisotropic conductive adhesive comprising a photo initiated adhesive;
applying pressure to seat the microelectronic device on the carrier and to complete the electrical connections between the conductive pads and the bonding pads through the anisotropic conductive adhesive;
and
exposing the back side of the carrier to a source of light comprising a wavelength within the first wavelength range such that the light waves within the first wavelength range are substantially transmitted through the flexible substrate to initiate the curing process of the anisotropic conductive adhesive, wherein the step of exposing the back side of the carrier to a source of light is carried out by means of an infrared laser having a wavelength of at least 1,060 nanometers.

2 more elements

Dependencies are inferred from the claim text.