Diffusion controlled reactions in Au/Pb–Sn solder system

The intermetallic compounds formed after reflow and burn-in testing of a Sn20In-0.8Cu solder ball grid array (BGA) package are investigated. Along with the formation of the Cu 6 (Sn 0.78 In 0.22 ) 5 precipitates (IM1) in the solder matrix, scallop-shaped intermetallic compounds (IM2) with a compositional mixture of Cu 6 (Sn 0.87 In 0.13 ) 5 and Ni 3 (Sn 0.87 In 0.13 ) 4 appear at the interfaces between the solder balls and Au/Ni/Cu pads. A significant number of intermetallic particles (IM3), with a composition of (Au 0.80 Cu 0.20 )(In 0.33 Sn 0.67 ) 2 , can also be found in the solder matrix. After aging at 115°C for 750 h, an additional intermetallic compound layer (IM4) with a composition of (Ni 0.91 Cu 0.09 ) 3 (Sn 0.77 In 0.23 ) 2 is formed at the interface between IM2 and the Ni layer. The ball shear strength of the Sn-20In-0.8Cu BGA solder after reflow is 4.5 N and will rise to maximum values after aging at 75°C and 115°C for 100 h. With a further increase of the aging time at both temperatures, the joint strengths exhibit a tendency to decline linearly at about 1.7 ϫ 10 -3 N/h.

Section: Resultssupporting

confidence: 66%

Reflow and burn-in of a Sn-20In-0.8Cu ball grid array package with a Au/Ni/Cu pad

Chiang

Chang

Chuang

2004

“…Three different IMC layers, AuSn, AuSn 2 , and AuSn 4 , are found on the Sn/Au interface annealed at 200°C for 100 h. The observation is similar to those of Chen and Yen 4 and Hannech et al 10 However, the different results can be observed as Cu added to Sn reacting with Au. Figure 10a is the BEI Investigation of the Phase Equilibria of Sn-Cu-Au Ternary and Ag-Sn-Cu-Au Quaternary Systems and Interfacial Reactions in Sn-Cu/Au Couples micrograph of the Sn-0.3wt.%Cu/Au reaction couple annealed at 200°C for 200 h. Except for the abovementioned three Au-Sn IMC layers, two new layers were formed.…”

Section: Interfacial Reaction Of Sn-cu/au Couplessupporting

confidence: 86%

“…There are some studies related to interfacial reactions between solders and Au. [2][3][4][5][6][7][8][9][10][11][12] Nakahara et al studied the reaction of a Sn/Au system at room temperature and found that there were f-solid solution, AuSn, AuSn 2 , and AuSn 4 phases between Sn and Au. 6,7 Hannech et al researched the reaction of Pb-72at.%Sn with Au at 80-160°C, and three intermetallic compound (IMC) layers, AuSn, AuSn 2 , and AuSn 4 phases, were found.…”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Investigation of the Phase Equilibria of Sn-Cu-Au Ternary and Ag-Sn-Cu-Au Quaternary Systems and Interfacial Reactions in Sn-Cu/Au Couples

Yen

Jao

Hsiao

et al. 2007

The phase equilibria of the Sn-Cu-Au ternary, Ag-Sn-Cu-Au quaternary systems and interfacial reactions between Sn-Cu alloys and Au were experimentally investigated at specific temperatures in this study. The experimental results indicated that there existed three ternary intermetallic compounds (IMCs) and a complete solid solubility between AuSn and Cu 6 Sn 5 phases in the Sn-Cu-Au ternary system at 200°C. No quaternary IMC was found in the isoplethal section of the Ag-Sn-Cu-Au quaternary system. Three IMCs, AuSn, AuSn 2 , and AuSn 4 , were found in all couples. The same three IMCs and (Au,Cu)Sn/ (Cu,Au) 6 Sn 5 phases were found in all Sn-Cu/Au couples. The thickness of these reaction layers increased with increasing temperature and time. The mechanism of IMC growth can be described by using the parabolic law. In addition, when the reaction time was extended and the Cu content of the alloy was increased, the AuSn 4 phase disappeared gradually. The (Au, Cu)Sn and (Cu , Au) 6 Sn 5 layers played roles as diffusion barriers against Sn in Sn-Cu/Au reaction couple systems.

“…Hence, the Ni layer is plated with a Au or Pd layer to improve corrosion resistance. [12][13][14][15] In the case of a multilayer Pd/Ni/Cu conductor with a thin Pd layer, the Pd layer quickly dissolves into a molten Sn-based solder during soldering, leaving the Ni layer in contact with the solder. As a result, the Ni layer reacts directly with the solder during solid-state energization heating.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Solid-State Reactive Diffusion in the (Pd-Ni)/Sn System

Hashiba

Shinmei

Kajihara

2011

The growth of compounds during energization heating at the interconnection between a Sn-based solder and a multilayer Pd/Ni/Cu conductor may be inhibited by the alloying of Pd with Ni. To examine such influence of Ni on the compound growth, the kinetics of solid-state reactive diffusion in the (Pd-Ni)/ Sn system was experimentally determined in the present study. Experiments were conducted using Sn/(Pd-Ni)/Sn diffusion couples with Ni mol fractions of y = 0.257, 0.505, and 0.746 which were prepared by a diffusion bonding technique. The diffusion couples were isothermally annealed in the temperature range of 433 K to 473 K for various times up to 771 h. During annealing, different compounds are formed as rather uniform layers at the interface in the diffusion couple. In all the annealed diffusion couples, (Pd,Ni)Sn 4 was observed clearly. Furthermore, (Pd,Ni)Sn 3 and (Pd,Ni)Sn 2 were recognized for y = 0.257, and Ni 3 Sn 4 was discerned for y = 0.746. However, no other compounds except (Pd,Ni)Sn 4 were detected for y = 0.505. The total thickness of the compound layers is proportional to a power function of the annealing time. The exponent of the power function is rather close to 0.5 for y = 0.257 and 0.505 but smaller than 0.5 for y = 0.746. Thus, volume diffusion is the ratecontrolling process of the compound growth for y = 0.257 and 0.505, but boundary diffusion contributes to the rate-controlling process for y = 0.746. At the experimental annealing times, the overall growth rate of the compound layers is insensitive to y at y < 0.5 but decreases monotonically with increasing value of y at y > 0.5. Consequently, the compound growth is actually decelerated by the addition of Ni into Pd with y > 0.5 in the multilayer Pd/Ni/Cu conductor.