Component Issues – Decreasing Pitch

Component Issues – Decreasing Pitch

Component Issues – Decreasing Pitch

Potential Issues:

– Paste Volume Control
– Component/PCB Flatness
• Internal Split Plane
• NFP Removal Impacts
– Component/PCB Warpage

LGA/QFN Package Assembly

Trace Routing Under Component Create Localized Height Variations
– Standoff Height Variation
Leadless Devices Are More Sensitive To PCB/Component Flatness/Warpage
– Received Condition
– In-process Condition (During Reflow/Rework Solder Process)

Solder wicking around NSMD pads produce significantly lower molten solder height.

Solder mask defined pads should be used for LGA and 0.4mm & smaller pitch BGA/CSP packages

Component Issues – LGA & QFN

Potential Issues:

– Land Pattern Design
• Pad Size Uniformity (SMD vs NSMD)
– Paste Volume Control
• Pad to Pad Volume
• Pad to Design Defined Volume
– Component/PCB Flatness
• Internal Split Plane
• NFP Removal Impacts
– Component/PCB Warpage
– Decrease Component Standoff Height
• Decreased Reliability

Trace Routing Impacts Solder Joint

Increased Mounting Pad Size Affected By:

• Number Of Trace Connections To Each Pad
• Width Of Trace Connections To Each Pad
• Size of Pad EFFECTIVE PAD SIZE ANALYSIS
• Size of Pad
– Small Pads Have Less Margin
• Uniformity Of Trace Egress Direction
– Some Package Types Are
More Sensitive Than Others
• Uniformity Of Trace Sizes

Trace Routing Impacts Solder Joint

• Gradient Of Different Trace Sizes
• Localized Concentrated Large Trace
Connections Increase Defect Potential

Concentrations Of Design Variability Can Create: Solder Bridge, Open Connection, Insufficient Solder, Tilted Components

Component Pad – Thermal Imbalance

• Multiple Trace Connections
– Number Of Trace Connections Per Pad
– Uniformity Across All Pads On Single Component
• Solder Mask Defined Pad
• Increased Soldering Defects
– Delayed Reflow Across SMT Components
• Tombstone Components
• “Ball in Socket” Area Array Component

• Small Passive Component Pad Design
– Mixed Solder Mask Defined
• Multiple/Large Trace
• Exposed Plane
– Smaller Component Package, The Component Pad – Thermal Imbalance
– Smaller Component Package, The Greater The Impact

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