Converting Ball Grid Array to Column Grid Array

November 1, 2005

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  • The availability of Military-grade electronics is declining
  • Ball Grid Array (BGA) is rapidly becoming the package style of choice in commercial electronics
  • For Military and Space environments, BGA packaging is a reliability compromise (BGAs lack compliant leads)
  • Modifications and ruggedization of packaging is essential for ensuring reliability of military electronics 4
  • Solder balls are less compliant than leads
  • Stress is induced by:
  • Coefficient of Thermal Expansion (CTE) mismatch (temperature cycle)
  • Thermal mismatch (power cycle)
  • Mechanical (warp, vibration, etc)
  • Stress increases with:
  • Distance from neutral point (larger packages)
  • Lower standoff height
Typical temp-cycle failure in high-lead ball
Ball Grid Array vs. Column Grid Array
  • Column Grid Array (CGA) is a flexible interconnect replacement for rigid solder balls
  • Higher standoff and compliance in the column alleviates CTE and thermal mismatch between the board and the component
Two diagrams compare solder ball (Lsb) and column (Lc) interconnects between a device and a board, labeling S, d, Lsb, and Lc.
A mathematical formula calculating maximum stress, σmax, using variables including thermal expansion, length, and modulus.
  • ΔT 1 = Temperature Change of Board
  • ΔT 2 = Temperature Change of Component
  • α 1 = CTE of the Board
  • α 2 = CTE of the Component
  • S = Distance from Neutral Point (DNP)
  • E = Modulus of Elasticity of Ball or Column
  • d = Diameter of Ball or Column
  • L = Standoff Height of Ball or Column
  • σ max = Maximum Stress
Wire Column

Wire Column

High-Lead wire attached with Sn63-Pb37 fillets

Reinforced Solder Column

Reinforced Solder Column

High-Lead wire core with spiral wrapped copper ribbon attached with Sn63-Pb37 fillets

Two CPU processors with pin grids shown from different angles on a dark, reflective surface.
Georgia Institute of Technology & IBM

Straight Wire Column


  • Finite element model showing location of maximum strain (Left)
  • Typical failure of non-reinforced column (Right)
A microscopic cross-section showing solder joints between a dark electronic component and a metallic circuit board base.

Copper Reinforced Column


  • Crack propagation abated
  • Redundancy without stiffness
  • Continues to function electrically even if core is cracked
Weibull plot comparing thermal cycle failure rates of BGA balls, wire columns, and reinforced columns.

Temperature Cycles –10 to +125 C All parts ceramic with 1.27mm pitch 625 pin package 32mm square


  • CBGA625 | BGA with high-Pb spheres
  • CCGA625 | CGA with straight wire columns
  • CCGA625R | CGA with reinforced columns
  • Many commercial components are not capable of meeting the environmental requirements of military and space applications
  • CGA modifications to commercial devices result in
  • Reliability Improvements
  • Robust Designs
  • Reinforced solder columns show a significant performance advantage in comparison to other solder columns
  • Military funding of this technology will allow significant improvements such as:
  • Optimize column design through finite element modeling and analysis of the reinforced column
  • Reliability testing and qualification of enhancements in design and materials
  • Development of a lead-free version

The author would like to thank Tom Clifford - Lockheed Martin and William Davis - Applied Material Technologies for their valuable analysis, discussions, and helpful input.


Bibliography


[1] D. Banks, D. Gerke, “Assembly and Reliability of Ceramic Column Grid Array

[2] A. Perkins, S. Sitaraman, “Thermo-mechanical Failure Comparison and Evaluation of CCGA and CBGA Packages

[3] T. Clifford, “Final Report – Phase 1 T-Cycle Test” Lockheed Martin Internal Document

[4] R. Winslow, “Converting Ball Grid Array Components to Column Grid Array” MASH 2005

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