Methods for attachment and devices produced using the methods
A technology for devices and supplies, applied in the field of attaching and using the devices produced, can solve the problems of damage to the die, poor device performance, limited life, etc.
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Embodiment 1
[0051] Nanosilver pastes containing capped silver particles were prepared as described in US Patent Application Serial No. 11 / 462,089. Briefly, the composition of the silver paste was 80 wt.% nano silver powder with cetylamine capping agent in an amount ranging from 0 to 15 wt.%. Butyl carbitol was used as solvent (19.5 wt.% in the slip) and the surfactant BYK163 (0.5 wt.% in the slip) was also present. The composition was first mixed for 1 minute at 2500 rpm in a high-speed mixer SpeedMixer DAC 150FVZ-K and then ground in a 3-roller mill from EXAKT. The resulting material is used to wet and bond solid surfaces at temperatures of 200-300°C during the sintering process.
[0052] Experiments done using nanosilver powders with different amounts of cetylamine capping agent showed that nanomaterials containing no or minimal amount of capping agent did not adhere to silicon or any other material. It also cannot be sintered into a dense structure without applying considerable exter...
Embodiment 2
[0055] Prepare the slurry, which has the following ingredients: 70wt.% nano-silver powder (based on the weight of the blocked nano-silver powder with 2wt.% HDA capping), 15wt.% butyl carbitol, 2wt.% toluene, 0.75wt. % dispersant Dysperbyk 163 and 0.5 wt.% wetting agent Sylquest A1100.
[0056] The paste was stencil printed onto a 25 mm x 25 mm alumina direct bonded copper (DBC) substrate from Curamic Electronics. The stencil thickness is 150 microns and the opening is 20 x 20 mm. A 15 x 15 mm silicon die with sputtered nickel / gold metallization was placed on the surface of the silver stamp. The assembly was processed according to the following conditions: drying at 50° C. for 5 minutes, then drying at 140° C. for 30 minutes, and finally sintering at 300° C. and a pressure of 5 MPa for 2 minutes.
[0057] The formed joints were examined with X-rays (see image 3 , X-ray photographs of the die attached to the copper heat sink) and SEM observations with cross-sections (see Fig...
Embodiment 3
[0060] Nanogold slurries containing capped gold particles can be prepared as described in US Patent Application Serial No. 11 / 462,089. The slurry may include gold particles capped with about 1-2% by weight capping agent. The capping agent may be cetylamine, dodecanethiol, or other amine- or thiol-based capping agents. Nano gold paste may be used to attach the die (or other electronic components) to the substrate.
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