New High-Speed 3D Surface Imaging Technology in Electronics Manufacturing Applications

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This paper introduces line confocal technology that was recently developed to characterize 3D features of various surface and material types at sub-micron resolution. It enables automatic microtopographic 3D imaging of challenging objects that are difficult or impossible to scan with traditional methods,such as machine vision or laser triangulation. Examples of well-suited applications for line confocal technology include glossy,mirror-like,transparent and multi-layered surfaces made of metals (connector pins,conductor traces,solder bumps etc.),polymers (adhesives,enclosures,coatings,etc.),ceramics (components,substrates,etc.) and glass (display panels,etc.). Line confocal sensors operate at high speed and can be used to scan fast-moving surfaces in real-time as well as stationary product samples in the laboratory. The operational principle of the line confocal method and its strengths and limitations are discussed. Three metrology applications for the technology in electronics product manufacturing are examined: 1. 3D imaging of etched PCBs for micro-etched copper surface roughness and cross-sectional profile and width of etched traces/pads. 2. Thickness,width and surface roughness measurement of conductive ink features and substrates in printed electronics applications. 3. 3D imaging of adhesive dots and lines for shape,dimensions and volume in PCB and product assembly applications.

Author(s)
Juha Saily
Resource Type
Technical Paper
Event
IPC APEX EXPO 2019

Head-on-Pillow Defect Detection - X-ray Inspection Limitations

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Both the number and the variants of Ball Grid Array packages (BGAs) are tending to increase on network Printed Board Assemblies (PBAs)with sizes ranging from a few mm die size Wafer Level Packages (WLPs) with low ball count up to large multi-die System-in-Package (SiP) BGAs with 60-70 mm side lengths and thousands of I/Os.
One big challenge,especially for large BGAs,SiPs and for thin fine-pitch BGA assemblies,is the dynamic warpage during the reflow soldering process. This warpage could lead to solder balls losing contact with the solder paste and its flux during parts of the soldering process and this may result in solder joints with irregular shapes,indicating poor or no coalescence between the added solder and the BGA balls. This defect is called Head-on-Pillow (HoP) and is a failure type that is difficult to determine.
In this study,x-ray inspection was used as a first step to find deliberately induced HoP defects,followed by pry-off of the BGAs to verify HoP defects and fault detection correlation between the two methods. The result clearly shows that many of the solder joints classified as HoP defects in the x-ray analysis have no evidence at all of HoP after pry-off. This illustrates the difficulty of determining where to draw the line between pass and fail for HoP defects when using x-ray inspection.

Author(s)
Lars Bruno,Benny Gustafson
Resource Type
Technical Paper
Event
IPC APEX EXPO 2019