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Wrap-resistant ultra-thin integrated circuit package fabrication method

  • US 5,864,175 A
  • Filed: 05/10/1996
  • Issued: 01/26/1999
  • Est. Priority Date: 03/29/1993
  • Status: Expired due to Term
First Claim
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1. A warp-resistant integrated circuit package manufactured in accordance with a method comprising the steps of:

  • providing an integrated circuit package having planar upper and lower major surfaces, an integrated circuit die, and a neutral thermodynamic axis that coincides with a plane approximately through the center of said die;

    reducing the overall thickness of said integrated circuit package by removing some casing material uniformly across said planar upper major surface;

    mounting a thin layer of material, and having a coefficient of thermal expansion less than or equal to the coefficient of thermal expansion of silicon to said uniformly reduced planar upper major surface of said integrated circuit package, wherein said thin layer of material extends to the perimeter of said upper major surface; and

    reducing the overall thickness of said integrated circuit package by removing some casing material uniformly across said planar lower major surface;

    wherein said thin layer of material is mounted on said package exterior; and

    wherein the thickness of said thin layer of material and its disposition relative to said selected axis are selected to minimize the vectorial summation of all moments acting on said package about said axis; and

    wherein the moment associated with each layer of material forming said package is calculated using the equation;

    
    
    space="preserve" listing-type="equation">m≈

    (E)(h)(t)Δ

    (a)Δ

    (T)where m is the moment of the layer;

    E is the Young'"'"'s modulus of elasticity of the layer material;

    h is the moment-arm distance of the center of the layer from said neutral thermodynamic axis;

    t is the layer thickness;

    Δ

    (a) is the difference in CTE between the layer and the material containing the neutral thermodynamic axis; and

    Δ

    (T) is the temperature difference between assembly bonding temperature and operation temperature.

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