Today＇s　3D　electronic　packaging　is　characterized　by　smaller　size　and　higher　functional　density,　which　generally　require　multiple　reflow　cycles.　However,　due　to　the　Ostwald　ripening　process　of　the　interfacial　intermetallic　compound　(IMC),　the　solder　joint＇s　strength　would　decrease　as　the　number　of　reflow　cycles　increases.　To　address　this,　we　developed　a　novel　composite　solder　by　incorporating　nickel-coated　carbon　fiber　(Ni@CF)　into　the　Sn-3.0Ag-0.5Cu　(SAC305)　solder　connection.　The　study　showed　that　Ni@CF　effectively　enhanced　the　stability　and　reliability　of　solder　joints　during　multiple　reflow　processes.　Compared　with　Ni@CF-free　equivalents,　Ni@CFs　promoted　the　nucleation　of　interfacial　IMC　during　the　solid-liquid　reaction　and　inhibited　Ostwald　ripening,　leading　to　a　refinement　of　the　interfacial　IMC　grains.　As　a　result,　the　interface　was　strengthened,　and　the　shift　of　shear　fracture　to　the　brittle　interface　seen　in　the　SAC305　solder　joint　with　multiple　reflows　did　not　occur　in　the　composite　solder　joint.　Furthermore,　carbon　fiber　strengthened　the　solder　matrix　through　the　load　transfer　and　shear-off　mechanisms,　depending　on　its　inclination　angle　with　the　shear　plane.　Consequently,　the　Ni@CFs-reinforced　solder　joints　maintained　a　shear　strength　of　over　42　MPa　throughout　ten　reflow　cycles,　while　the　pristine　SAC305　solder　joint　exhibited　decreased　shear　strength　to　33　MPa.　This　study　provides　new　insights　into　composite　solder　joints＇　stability　and　reinforcement　characteristics　when　subjected　to　multiple　reflows.