Abstract: Soldering process was used to join LTCC circuit substrate and package carrier,the strength and failure characteristics of soldered joint of large size LTCC circuit substrate and package carrier were analyzed. The results showed that the average shear strength of large area soldered joint of LTCC circuit substrate（Au/Pt/Pd pad） and package carrier（surface coating Au 0. 5 μm） with Sn63 Pb37 eutectic solder was 28. 21 MPa,while the shear strength of abnormal samples were about 30% of the average value. The LTCC pads were loose with dense perforating holes. Sn elements of Sn-Pb solders entered into LTCC pads through holes after soldering. Some Sn elements reached the interface of LTCC pads and LTCC circuit substrate,and then formed a large area of non-dendritic AuSn₄ inside the LTCC pads. Compared to the normal samples,the sintering bonding strength between LTCC pads and LTCC circuit substrate of abnormal ones was lower,which was the main reason of interface failure and decreasing shear strength.