Effects of Zn-Bearing Flux on Joint Reliability and Microstructure of Sn-3.5Ag Soldering on Electroless Ni-Au Surface Finish

Abstract Radar is currently employed in automotive applications to provide the range, angle, and velocity of objects using RF waves (77GHz). This paper outlines solder joint reliability of a specific micro-processor that processes data received from a SRR (short range radar operating from 0.2 to 30 meters). It is a powerful digital signal processing accelerator, which targets safety applications that require a high Automotive Safety Integrity Level (ASIL-B). The paper explores the package design and construction, SMT (surface mount technology) assembly, and board level reliability testing of various BGA pad surface finish and solder ball alloy materials on a 0.65 mm pitch, 10 × 10 mm body 141 MAPBGA (mold array process-ball grid array) package. The package configurations include two BGA pad surface finishes (Ni/Au and OSP [organic solderability protectant]) and three solder alloys (SnAg, SAC405, and SAC-Bi [a Bi containing SAC derivative]). Solder joint reliability analysis was performed through AATS (air-to-air thermal shock) between 40°C and +125°C and JEDEC Drop Testing at 1500G's. Thermal shock was extended until at least 75% of the populations failed, which was well past the points needed to qualify the packages for the intended end-use applications. The evaluations of the micro-processor indicate that the MAPBGA package can meet the ASIL-B specification requirements with optimized combinations of BGA pad surface finish and solder alloy. The focus of this paper was to determine the baseline solder-joint thermal shock and JEDEC drop performance with varied BGA pad surface finish and solder ball alloy materials.

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Effect of Ag Content on Mechanical Properties of Lead-Free Sn-Ag-Cu-Ni-Ge Alloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.462-463.82 ◽

2011 ◽

Vol 462-463 ◽

pp. 82-87 ◽

Cited By ~ 1

Author(s):

Ikuo Shohji ◽

Ryohei Arai ◽

Hisao Ishikawa ◽

Masao Kojima

Keyword(s):

Tensile Strength ◽

Exposure Time ◽

Shear Force ◽

Heat Exposure ◽

Lead Free ◽

Exposure Treatment ◽

Ball Shear ◽

Joint Reliability ◽

Solder Balls ◽

Electroless Ni

The tensile properties of Sn-x(x=1, 2, 3)Ag-0.5Cu-0.05Ni-0.005Ge (mass%) alloys were investigated. In addition, the ball shear force was investigated with solder balls and two types electrodes, Cu and electroless Ni/Au plated Cu, to examine joint reliability under heat exposure conditions. Tensile strength of the alloy decreases with decreasing the Ag content. On the contrary, elongation increases with decreasing the Ag content. When the Ag content reduces, primary β-Sn phases are coarsened and eutectic microstructures diminish. The decrease of the eutectic microstructures causes a reduction of the tensile strength. In as-soldered joints with Sn-Ag-Cu-Ni-Ge solder balls and Cu electrodes, the ball shear force increases with increasing the Ag content. However, the ball shear force decreases with increasing heat exposure time. After heat exposure treatment at 423 K for 500 h, the ball shear force is relatively stable at lower values regardless of the Ag content. In the joints with electroless Ni/Au plated Cu electrodes, the ball shear force slightly increases with increasing heat exposure time. Even after heat exposure treatment at 423 K for 500 h, hierarchy of the ball shear force is maintained. The ball shear force becomes high with increasing the Ag content.

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