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LCCC failure rate

The LCCC has the highest failure rate of all component types, especially with larger sizes of package, because of:

• the large TCE differences between body and substrate, leading to significant thermal mismatch
  
  
• the high thermal conductivity of the ceramic body, increasing the possibility of local thermal gradients
  
  
• the lack of compliance of the joints
  
  
• the comparatively weak bonds between the package metallisation and the ceramic body
  
  
• the stiffness of the LCCC body
  
  
• the small size of the joints.

One solution to the LCCC surface mounting problem is to reduce the TCE of the laminate by including a thin sheet of a low-expansion material such as copper-invar.

But everything comes at a price; by reducing the in-plane TCE, the Z-axis expansion increases as a result of the Poisson strain ratio being affected by the copper-invar lamination. This results in more plated through-hole cracks.

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