Crystalline　and　amorphous　cobalt-phosphorus　(Co-P)　coatings　have　their　own　advantages　in　interfacial　dif-fusion　resistance　and　mechanical　ductility　of　solder　joints,　respectively,　but　it　cannot　be　better　at　both.　In　this　work,　the　hybrid　crystalline-amorphous　Co-P　coating　(Co-9.1　at.%　P)　was　fabricated　and　applied　on　the　Cu/Sn　interface　by　controlling　the　crystallinity　through　compositional　design.　Combining　the　advan-tages　of　crystalline　and　amorphous　Co-P,　strategies　for　solder　joints　with　high　shear　strength,　ductile　inter　-metallic　compounds　(IMCs)　and　slow　interface　consumption　was　proposed.　The　evolution,　microstructure,　phase,　and　mechanical　properties　of　the　Co-Sn,　Co-Sn-P　and　P-rich　layers　in　solid-state　diffusion　were　sys-tematically　characterized　and　tested　by　means　of　SEM,　EPMA,　EBSD,　TEM,　nanoindentation,　and　shear　test.　It　was　found　that　the　hybrid　Co-P　coating　achieved　a　low　consumption　rate,　14.2　nm/h,　attributing　to　the　par-tially　crystalline　structure　and　the　Co-Sn-P　exfoliation　behavior.　In　addition,　solder　joints　containing　large　-thickness　ductile　Co-Sn　IMCs,　3.2-3.6　GPa　of　hardness,　was　established.　The　shear　strength　after　aging　reached　75.4　MPa　relying　on　the　large　thickness　of　Co-Sn　IMCs.　Severe　mechanical　loads　would　be　able　to　be　withstand　by　virtue　of　the　plastic　deformation　of　ductile　IMCs.　Hybrid　crystalline-amorphous　Co-P　would　be　a　promising　interface　material　in　microelectronic　packaging.(c)　2022　The　Authors.　Published　by　Elsevier　Ltd.　This　is　an　open　access　article　under　the　CC　BY-NC-ND　license　(http://creativecommons.org/licenses/by-nc-nd/4.0/).