Method, apparatus, and structure for determining interposer thickness

Patent metadata

Field	Value
Publication number	US-9568405-B2
Application number	US-201414554088-A
Country	US
Kind code	B2
Filing date	Nov 26, 2014
Priority date	Nov 29, 2013
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

The present invention includes the following steps: setting the thickness of an interposer to an initial value; determining the axial force of the interposer and the radius of curvature of the warpage caused by the difference in the thermal expansion coefficients of the supporting substrate, the joined layer and the interposer at the set thickness; determining the absolute value of the stress on the chip-connecting surface of the interposer from the stress due to the axial force of the interposer and the stress due to the warpage using the determined axial force and the radius of curvature; determining whether or not the absolute value of the stress is within a tolerance; changing the thickness of the interposer by a predetermined value; and confirming the set thickness as the thickness of the interposer when the determined absolute value of the stress is within the tolerance.

First claim

What is claimed is:

1. A chip mounting structure comprising:
a flip chip,
an interposer whose obverse surface is connected to the flip chip,
a supporting substrate connected to the reverse surface of the interposer, and
a joined layer provided between the interposer and the supporting substrate,
wherein the thickness of the interposer is determined by:
setting the thickness of the interposer to an initial value;
determining an axial force of the interposer and a radius of curvature of a warpage caused by a difference in thermal expansion coefficients of the supporting substrate, the joined layer, and the interposer at the set thickness;
determining, using the determined axial force and radius of curvature, the absolute value of a first stress on a chip-connecting surface of the interposer from a second stress due to the axial force of the interposer and a third stress due to the warpage;
determining whether the absolute value of the first stress is within a tolerance;
changing the thickness of the interposer by a predetermined value, when the determined absolute value of the first stress is not within the tolerance, and repeating the steps of determining the axial force of the interposer and the radius of curvature, determining the absolute value of the first stress on the chip-connecting surface of the interposer, and determining whether the determined absolute value of the first stress is within the tolerance; and
confirming the set thickness as the thickness of the interposer when determined absolute value of the first stress is within the tolerance.

2. The chip mounting structure of claim 1 , wherein determining the axial force of the interposer and the radius of curvature of the warpage further comprises:
generating a system of equations derived from the continuity of the strain at the interface for, the balance of axial force for, and the balance of the bending moment for the supporting substrate, the joined layer, and the interposer; and
calculating the axial force and the radius of curvature of the warpage by solving the system of equations for an axial thrust of the interposer and the radius of curvature of the warpage;
wherein the system of equations is generated using:
the Young's modulus and thermal expansion coefficient of the supporting substrate, the joined layer, and the interposer;
the desired thickness of the supporting substrate and the joined layer; and
the set thickness of the interposer.

3. The chip mounting structure of claim 2 , wherein the Young's modulus and the thermal expansion coefficient of the joined layer are the Young's modulus and the thermal expansion coefficient calculated from the metal properties of a complex between a metal joined portion and an underfill resin portion.

4. The chip mounting structure according of claim 1 , wherein determining the absolute value of the stress on the chip-connecting surface of the interposer further comprises:
calculating a second stress due to the axial force of the interposer by dividing the axial force of the interposer by a desired width of the interposer and the set thickness;
calculating a third stress due to the warpage of the interposer by multiplying the Young's modulus of the interposer by half of the set thickness, and dividing the product by the radius of curvature of the warpage of the interposer; and
calculating the total stress due to the axial force of the interposer and the third stress due to the warpage.

5. The chip mounting structure of claim 1 , wherein the interposer is a silicon interposer, and the supporting substrate is an organic substrate.

6. A method comprising:
setting the thickness of an interposer to an initial value, where the interposer is connected via a joined layer to a supporting substrate;
determining an axial force of the interposer and a radius of curvature of a warpage caused by a difference in thermal expansion coefficients of the supporting substrate, the joined layer, and the interposer at the set thickness;
determining, using the determined axial force and radius of curvature, the absolute value of a first stress on a chip-connecting surface of the interposer from a second stress due to the axial force of the interposer and a third stress due to the warpage;
determining whether the absolute value of the first stress is within a tolerance;
changing the thickness of the interposer by a predetermined value, when the determined absolute value of the first stress is not within the tolerance, and repeating the steps of determining the axial force of the interposer and the radius of curvature, determining the absolute value of the first stress on the chip-connecting surface of the interposer, and determining whether the determined absolute value of the first stress is within the tolerance; and
confirming the set thickness as the thickness of the interposer when the determined absolute value of the first stress is within the tolerance.

7. The method of claim 6 , wherein the step of determining the axial force of the interposer and the radius of curvature of the warpage further comprises the steps of:
generating a system of equations derived from the continuity of the strain at the interface, the balance of the axial force, and the balance of the bending moment for the supporting substrate, the joined layer, and the interposer; and
calculating the axial force and the radius of curvature of the warpage by solving the system of equations for an axial thrust of the interposer and the radius of curvature of the warpage;
wherein the system of equations is generated using:
the Young's modulus and thermal expansion coefficient of the supporting substrate, the joined layer, and the interposer;
the desired thickness of the supporting substrate and the joined layer; and
the set thickness of the interposer.

8. The method of claim 7 , wherein the Young's modulus and the thermal expansion coefficient of the joined layer are the Young's modulus and the thermal expansion coefficient calculated from the metal properties of a complex between a metal joined portion and an underfill resin portion.

9. The method of claim 6 , wherein the step of determining the absolute value of the stress on the chip-connecting surface of the interposer further comprises the steps of:
calculating a second stress due to the axial force of the interposer by dividing the axial force of the interposer by a desired width of the interposer and the set thickness;
calculating a third stress due to the warpage of the interposer by multiplying the Young's modulus of the interposer by half of the set thickness, and dividing the product by the radius of curvature of the warpage of the interposer; and
calculating the total stress due to the axial force of the interposer and the third stress due to the warpage.

10. An interposer connected via a joined layer to a supporting substrate, the thickness of the interposer being determined by:
setting the thickness of the interposer to an initial value;
determining an axial force of the interposer and a radius of curvature of a warpage caused by a difference in thermal expansion coefficients of the supporting substrate, the joined layer, and the interposer at the set thickness;
determining, using the determined axial force and radius of curvature, the absolute value of a first stress on a chip-connecting surface of the interposer from a second stress due to the axial force of the interposer and a third stress due to the warpage;
determining whether the absolute value of the first stress is within a tolerance;
changing the thickness of the interposer by a predetermined value, when the determined absolute value of the first stress is not within the tolerance, and repeat

Assignees

• IBM

Inventors

• Hada Sayuri
• Horibe Akihiro
• Matsumoto Keiji

Classifications

• G01L1/26 Primary

  Auxiliary measures taken, or devices used, in connection with the measurement of force, e.g. for preventing influence of transverse components of force, for preventing overload · CPC title

• G01N3/20

  by applying steady bending forces (G01N3/26, G01N3/28 take precedence) · CPC title

• G01N3/22 Primary

  by applying steady torsional forces (G01N3/26, G01N3/28 take precedence) · CPC title

• G01N25/16

  by investigating thermal coefficient of expansion · CPC title

• G01N2203/0057

  using stresses due to heating, e.g. conductive heating, radiative heating · CPC title