- Xclean scrubbing sponges dowin enterprises how to#
- Xclean scrubbing sponges dowin enterprises verification#
The Sn atoms in the molten solder diffuse inward into Ni(P), forming Ni 3Sn 4 and expelling P. When a molten solder joint contacts with an electroless Ni / Au finish, the Au dissolves into the molten solder, exposing Ni whose surface is enriched with P. XPS analysis and EDXA (Energy Dispersive X-ray Analysis) of the fracture surfaces indicated that the fracture occurred at the transition region where Sn, P, and Ni concentrations abruptly changed. X-diffraction of fresh Cu / electroless Ni / Au finishes showed that the Ni was amorphous with supersaturated P. XPS (X-ray Photoelectron Spectroscopy) analysis of fresh Cu / electroless Ni / Au finishes revealed that phosphorous, which was introduced in the Ni during electroless Ni plating, accumulated at the Ni / Au interface.
Xclean scrubbing sponges dowin enterprises how to#
This paper will give the reader a basic understanding of how to recognize black pad and subsequently determine its severity.Ī brittle fracture at the interface between solder joint and PCB (printed circuit board) pad was observed in some BGA (ball grid array) packages soldered on Cu / electroless Ni / Au metallization. We have had the opportunity to examine many different cases of black pad, from severe to mild, and have a large amount of knowledge to share. In severe cases, black pad defect can cause solderability issues and retard the formation of tin-nickel intermetallic preventing good wetting of the solder joint.
One failure mechanism associated with black pad defect is the brittle failure of well wetted solder joints from the underlying Ni-P layer due to the presence of the high phosphorus region. Black pad defect can manifest as corrosion spikes at the nodule boundaries in the Ni-P and can progress to an abnormally thick high phosphorus region at the top of the Ni-P. Most of the available literature suggests black pad defect is caused by accelerated reduction (corrosion) of the nickel in the nickel- phosphorus (Ni-P) layer during the immersion gold step of the ENIG process. One of the pitfalls of this surface finish is the possibility of creating a layer of overly elevated phosphorous content between the electroless nickel and immersion gold, known as black pad defect. The advent of the RoHS legislation, which mandated lead-free solders, and the rise in popularity of the BGA package, have resulted in ENIG becoming a popular choice for surface finish due to its excellent long term solderability and surface planarity. Copyright © 2014 IMAPS - International Microelectronics Assembly and Packaging Society All Rights Reserved. To mitigate the effects of discoloration at the electronic assembly level, a tinning process was implemented to prevent nickel plating oxidation and to ensure that good wettability for reliable solder joints was maintained.
Subsequent introduction of a nickel controller into the ENIG line were the implemented countermeasures. The root cause of ENIG pad discoloration and pitting was traced back to poor ENIG line process controls. These open nickel boundaries were attributed to the corrosive environment within ENIG plating, which resulted in the pad surface discoloration. The resulting analysis revealed a highly porous electroless nickel coating with deep crevasses and fissures penetrating down to the base copper (Cu) layer. Concurrently, metallurgical analysis of ENIG pads was performed, where samples were subjected to scanning electron microscopic/energy dispersive x-ray spectroscopic (SEM/EDX) cross section analysis, Auger electron spectroscopy (AES) and gold (Au) and electroless nickel (Ni) surface examination. Effects of thermal processes, cleaning methods, soldering, parylene deposition and factory cleanliness were examined thoroughly. The launched failure analysis involved evaluation of manufacturing processes suspected to contribute to the cause of the condition.
Manifestation of such latent anomaly was observed in the form of ENIG pad discoloration with variations from yellow, red or grey discolored surfaces to a more pronounced plating degradation, such as corrosive pitting. That poses challenges in the manufacturing environment, where resulting latent defects are detected in downstream processes but not at upfront incoming inspection.
Xclean scrubbing sponges dowin enterprises verification#
Coupled with visual examination, this verification method suffices for general PCB acceptance but may not be robust enough in cases where ENIG plating in PCBs is compromised. The most common is an IPC-4552 mandated plating thicknesses verification of 3-6μm and a minimum of 0.05μm for nickel and gold, respectively. Manufacturing of electronic assemblies using printed circuit boards (PCBs) with electroless nickel/immersion gold (ENIG) surface finishes requires front-end PCB evaluation that will guarantee that good quality product enters the assembly line.
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