Apparatus and method for determining failure mode in a shear or pull test device

• US 7,748,278 B2
• Filed: 03/08/2007
• Issued: 07/06/2010
• Est. Priority Date: 03/08/2006
• Status: Active Grant

• Current Assignee: Nordson Corporation
• Original Assignee: Nordson Corporation
• Inventors: Sykes, Robert John
• Primary Examiner(s): Noori; Max
• Application Number:
  US12/280,235
• Publication Number:
  US 20090056469A1
• Time in Patent Office: 1,216 Days
• Field of Search: 738/27, 73841-842, 738/50
• US Class Current: 73/827
• CPC Class Codes: G01N 19/04 Measuring adhesive force between materials, e.g. of sealing tape, of coating
• CPC Class Codes: G01N 2203/0218 Calculations based on experimental data
• CPC Class Codes: G01N 2203/0623 using piezoelectric gauges
• CPC Class Codes: G01N 2203/0676 Force, weight, load, energy, speed or acceleration
• CPC Class Codes: G01N 3/24 by applying steady shearing forces G01N3/26, G01N3/28 take precedence

Abstract

A method and apparatus for determining a mode of failure of a bond between an electrically conductive ball deposit and a substrate when breaking the ball deposit off of the substrate. The method and apparatus utilize tool force and displacement values to plot a force/displacement curve. The force/displacement curve is used to calculate the energy necessary to break the ball deposit off of the substrate. The energy value of a portion of a force/displacement curve is selected by reference to a peak force. In one preferred embodiment, this energy value is compared with a predetermined reference energy value to indicate a mode of failure. The peak force is preferably the maximum peak force, hi the preferred embodiment, the method and apparatus distinguish between a ductile failure mode and a brittle failure mode.

Claims

1. A method of determining the mode of bond failure of an electrically conductive ball deposit on a substrate which is subjected to a breaking force by a tool to break the ball deposit off the substrate by breaking the bond therebetween, the method comprising the steps of:

producing electrical force signals which indicate the force on the tool while the tool is breaking the ball deposit off the substrate,

producing electrical tool displacement signals which indicate the displacement of the tool while the tool is breaking the ball deposit off the substrate;

processing the electrical force signals to determine a selected peak breaking force,

utilizing the electrical force signals and electrical tool displacement signals to determine an associated value of energy absorbed by the ball deposit by reference to said selected peak breaking force, and

comparing said associated value of energy to a reference value of energy to indicate a mode of failure.

2. A method according to claim 1 wherein said associated value is determined to be one of energy absorbed prior to said selected peak, and energy absorbed after said selected peak.

3. A method according to claim 1 wherein said selected peak is determined to be the maximum applied force.

4. A method according to claim 3 wherein said selected peak is determined to be the sole peak.

5. A method according to claim 3 wherein a peak is discarded if the next succeeding minimum has a value greater than a pre-determined percentage of the value of that peak.

6. Shear testing apparatus for applying a shear force to an electrically conductive ball deposit on a substrate to shear the ball deposit off the substrate and indicate the quality of the bond between the ball deposit and the substrate, comprising:

a support for holding the substrate, the substrate having one or more ball deposits bonded to the substrate,

a shear tool mounted within said test apparatus for applying a shear force to an electrically conductive ball deposit on the substrate,

a force monitoring detector for generating electrical force signals representative of the force applied by the shear tool to the ball deposit during at least a part of the time that the shear tool is shearing the ball deposit off of the substrate,

a displacement monitoring detector for generating electrical displacement signals representative of the displacement of said shear tool by reference to said support during at least a part of the time that the shear tool is shearing the ball deposit off of the substrate,

a computer processor adapted to receive said force signals and displacement signals and to utilize said force signals and displacement signals to determine the absorption of energy by said ball deposit during at least a part of the time that said ball is being sheared from said substrate by said shear tool,

said computer processor furthered being adapted to utilize said force signals to determine a peak force value,

said computer processor still further being adapted to determine the portion of energy absorbed by said ball deposit by reference to said peak force value,

and said computer processor still further being adapted to utilize said portion of energy to indicate a mode of failure experienced by said ball deposit as said ball deposit was sheared from said substrate.

8. Apparatus according to claim 6 and further including a filter adapted to eliminate one or more peaks of transient force which are of less than pre-determined significance.

7. Pull testing apparatus for applying a pull force to an electrically conductive ball deposit on a substrate to break the ball deposit off the substrate and indicate the quality of the bond between the ball deposit and the substrate, comprising:

a support for holding the substrate, the substrate having one or more ball deposits bonded to the substrate,

a pull tool mounted within said test apparatus for applying a pull force to an electrically conductive ball deposit on the substrate,

a force monitoring detector for generating electrical force signals representative of the force applied by the pull tool to the ball deposit during at least a part of the time that the pull tool is breaking the ball deposit off of the substrate,

a displacement monitoring detector for generating electrical displacement signals representative of the displacement of said pull tool by reference to said support during at least a part of the time that the pull tool is breaking the ball deposit off of the substrate,

a computer processor adapted to receive said force signals and displacement signals and to utilize said force signals and displacement signals to determine the absorption of energy by said ball deposit during at least a part of the time that said ball is being broken from said substrate by said pull tool,

said computer processor furthered being adapted to utilize said force signals to determine a peak force value,

said computer processor still further being adapted to determine the portion of energy absorbed by said ball deposit by reference to said peak force value,

and said computer processor still further being adapted to utilize said portion of energy to indicate a mode of failure experienced by said ball deposit as said ball deposit was sheared from said substrate.

9. A method of determining the mode of bond failure of an electrically conductive ball deposit on a substrate which is subjected to a breaking force by a tool to break the ball deposit off the substrate and break the bond therebetween, the method comprising the steps of:

producing electrical force signals which indicate the force on the tool during at least a part of the time that the tool is breaking the ball deposit off the substrate,

producing electrical tool displacement signals which indicate the displacement of the tool during at least a part of the time that the tool is breaking the ball deposit off the substrate;

processing the electrical force signals to determine a selected peak breaking force,

utilizing the electrical force signals and electrical tool displacement signals to determine a first associated value of energy absorbed by the ball deposit prior to said selected peak breaking force and to determine a second associated value of energy absorbed by the ball deposit after said selected peak breaking force, and

comparing said first and second associated values of energy to indicate a mode of failure.