A new multilayer metallization, ENEPIG (electroless nickel electroless palladium immersion gold) with 0.1㎛ thin Ni(P) layer (thin-ENEPIG), was plated on a Cu PCB substrate for fine-pitch package applications. We evaluated interfacial reactions and mechanical reliability of a Sn-3.0Ag-0.5Cu (SAC305) solder alloy on a thin ENEPIG coated substrate during various reflow times. In the initial soldering reaction, (Au,Cu)Sn 4 intermetallic compound (IMC) formed at the SAC305/ENEPIG interface. After prolonged reflow reactions, the Pd and Ni layers were consumed, and (Cu,Ni) 6 Sn 5 IMC formed on the Cu layer. As the reflow time increased, the Cu and Ni contents in (Cu,Ni) 6 Sn 5 IMC increased and decreased, respectively, due to the limited Ni layer in the ENEPIG plating layer. In the low-speed shear test, all fractures occurred in the bulk solder regardless of reflow times. In the high-speed shear test, the fracture mode was changed from ductile to brittle with increasing reflow time, due to the formation of the thick interfacial IMC.

In this paper, we evaluated the interfacial reactions and brittle fracture behaviors of thin electroless nickel-electroless palladium-immersion gold (ENEPIG) plating layers with different Ni and Pd thicknesses for fine-pitch package applications. Firstly, the interfacial reactions and mechanical reliability of Sn-3.0Ag-0.5Cu (SAC305)/thin ENEPIG solder joints were evaluated. (Cu,Ni) 6 Sn 5 intermetallic compound (IMC) was formed at all of the thin ENEPIG interfaces, and P-rich Ni layer was also observed at the joint interface of the Pd substrate with 0.3 ㎛ Ni thickness. The interfacial IMC thickness decreased with increasing Ni and Pd thicknesses. In addition, the IMC thickness was affected by the contents of the Pd plating layer. The IMC thickness for the Pd-P substrate was thicker than that for the Pd substrate. In the high-speed shear test, the brittle fracture rate decreased with increasing Ni and Pd thickness. Also, the brittle fracture rate was affected by the components of the Pd plating layer, and the brittle fracture rate for the Pd substrate was lower than that for the Pd-P substrate. The ENEPIG joint with thicker Ni plating layer had superior interfacial stability and mechanical reliability.

Parosteal lipoma is a rare type of lipoma, the incidence being approximately 0.3% of all lipomas. Moreover, parosteal lipoma coexisting with osteochondroma is extremely rare. A few cases with coexistence of osteochondroma and parosteal lipoma have been reported and they were thought to be reactive changes of adjacent bone by parosteal lipoma. However, temporal relationship of these tumors could not be explained. Here, we report a case of parosteal lipoma associated with osteochondroma of the right ilium developed over 6 years, with follow-up radiographs.