Methods for assembling electronic devices with adhesive
An electronic device may have housing structures, electrical components, and other electronic device structures. Adhesive may be used to join electronic device structures. Adhesive may be dispensed as liquid adhesive and cured to form adhesive joints. Adhesive joints may be debonded. Chain reactions may be initiated by applying a localized initiator such as a chemical or localized energy to the adhesive. Once initiated, the chain reaction may spread throughout the adhesive to cure the adhesive, to globally change adhesive viscosity, or to weaken the adhesive to facilitate debonding. Local changes to adhesive may also be made such as local increases and decreases to adhesive viscosity. Chain reaction curing may be used to cure adhesive or debond adhesive that is hidden from view within gaps in the electronic device structures. Viscosity changes may be used to control where adhesive flows.
1. A method for attaching structures in an electronic device, comprising:
dispensing adhesive in a gap within the structures; and
in a localized area of the adhesive that is uncovered by the structures, initiating a chain reaction in the adhesive that changes all of the adhesive both inside and outside of the gap, wherein initiating the chain reaction comprises applying energy to only the localized area.
2. The method defined in claim 1 wherein applying the energy to only the localized area comprises:
applying light to only the localized area.
3. The method defined in claim 1 wherein applying the energy to only the localized area comprises:
applying heat to only the localized area.
4. The method defined in claim 1 wherein applying the energy to only the localized area comprises applying sound to only the localized area.
5. The method defined in claim 1 wherein initiating the chain reaction comprises initiating an adhesive curing chain reaction that cures all of the adhesive.
6. The method defined in claim 1 wherein initiating the chain reaction comprises initiating an adhesive-viscosity-increasing chain reaction that increases adhesive viscosity for all of the adhesive.
7. The method defined in claim 1 wherein initiating the chain reaction comprises initiating an adhesive-viscosity-decreasing chain reaction that decreases adhesive viscosity for all of the adhesive.
8. The method defined in claim 1 wherein initiating the chain reaction comprises initiating an adhesive-weakening chain reaction to debond the adhesive.
9. A method, comprising:
dispensing liquid adhesive on an electronic device structure, wherein the electronic device structure includes a localized area with adhesive-viscosity-increasing material;
increasing the viscosity of the liquid adhesive with the adhesive-viscosity-increasing material by flowing the dispensed liquid adhesive until the liquid adhesive reaches the adhesive-viscosity-increasing material, wherein reaching the adhesive-viscosity-increasing material causes only portions of the liquid adhesive that are adjacent to the adhesive-viscosity-increasing material to increase in viscosity; and
applying localized energy to only the portions of the liquid adhesive that are adjacent to the adhesive-viscosity-increasing material, wherein applying the localized energy initiates a chain reaction in the adhesive that spreads throughout all of the adhesive.
10. The method defined in claim 9 wherein the electronic device structure includes an integrated circuit and a printed circuit board to which the integrated circuit is mounted, and wherein the adhesive-viscosity-increasing material comprises material on the printed circuit board.
11. The method defined in claim 9 further comprising:
decreasing the viscosity of the liquid adhesive with adhesive-viscosity-decreasing material.
12. The method defined in claim 11 wherein decreasing the viscosity comprises flowing the dispensed liquid adhesive until the liquid adhesive reaches the adhesive-viscosity-decreasing material.