The effect of modifications to the nickel/gold surface finish on assembly quality and attachment reliability of a plastic ball grid array (peer review version)

Abstract

Electrolytic and electroless Ni/Au are common pad surface finishes on area array (BGA or CSP) packages and printed wiring boards (PWB). The electroless nickel/immersion gold (ENIG) process often is implemented when there is insufficient space to allow bussing for the more common electrolytic Ni/Au plating. The ENIG process continues to be used despite evidence that it may cause catastrophic, brittle, interfacial solder joint fractures. In this investigation a plastic ball grid array (PBGA) test vehicle is used to compare quality and reliability of standard and experimentally modified ENIG surface finishes. The standard electrolytic Ni/Au surface finish is used as the control cell for the experiment. Ball shear tests and optical and scanning electron microscopy are performed on as-received and thermally preconditioned packages to evaluate package quality prior to assembly. Accelerated temperature cycling (0 +100 C and 40 +125 C) is used to evaluate solder joint attachment reliability. Detailed failure mode analysis is used to compare the fracture modes in the ball shear and thermal cycled samples in the electroless and electrolytic packages. The results are discussed in terms of the failure modes and the characteristics of the different Ni/Au surface finishes.

Intermetallics Characterization of Lead-Free Solder Joints under Isothermal Aging

“…The amount of phosphorus needs to be controlled, depending on the plating process, to eliminate the possibility of black pad. 19 Elemental analysis was conducted using an energy dispersive x-ray (EDX). The layer between the solder and the copper above the Ni layer was found to be phosphorus rich, indicating the possible presence of blackpad.…”

Interfacial microstructure and shear behavior of Sn–Ag–Cu solder balls joined with Sn–Zn–Bi paste

“…It has been reported that the growth rate of intermetallic compounds is lower in the electrolytic Ni/solder and electroless Ni-P/solder systems than that in the Cu/solder system [15][16][17]. Previous studies also indicated that electrolytic Ni plating had a higher solder joint reliability than electroless Ni plating [16,18,19]. In addition, a gold layer, plated on the Ni layer of the metallized pads, not only improves wettability but also increases oxidation resistance [14].…”

Solid–Solid Reaction Between Sn-3Ag-0.5Cu Alloy and Au/Pd(P)/Ni(P) Metallization Pad with Various Pd(P) Thicknesses

“…An appropriate Pd(P) layer prevents the Ni(P) layer from being attacked by the Au plating bath; thus, galvanic hypercorrosion of the Ni(P) layer (generally termed ''black pads'') can be significantly reduced. [6][7][8][9][10] The Au and Pd(P) finishes are customarily deposited within a range of 0.05 lm to 0.3 lm (thickness) in realistic applications of the Au/Pd(P)/ Ni(P) surface finish. 11 The influence of the Pd(P) thickness on the soldering reaction between the Sn-3Ag-0.5Cu alloy and the trilayer structure [i.e., Au/Pd(P)/Ni(P)] has recently been examined by Ho et al 12 The reaction refers to a liquid-solid reaction in which the Sn-3Ag-0.5Cu alloy is a liquid but the Au/Pd(P)/Ni(P) trilayer is solid.…”