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US-12628683-B2 - Methods of improving wire bonding operations

US12628683B2US 12628683 B2US12628683 B2US 12628683B2US-12628683-B2

Abstract

A method of determining a new search height for a wire bonding process is provided. The method includes the steps of: providing a search height; performing a plurality of wire bonding operations using the search height; monitoring wire bonding evaluation criteria during each of the plurality of wire bonding operations; and determining a new search height using the monitored wire bonding evaluation criteria.

Inventors

  • Hui Xu
  • Wei Qin
  • JeongHo Yang

Assignees

  • KULICKE AND SOFFA INDUSTRIES, INC.

Dates

Publication Date
20260512
Application Date
20230425

Claims (20)

  1. 1 . A method of determining a new search height for a wire bonding process, the method comprising steps of: (a) providing a search height; (b) performing a plurality of wire bonding operations using the search height; (c) monitoring wire bonding evaluation criteria during each of the plurality of wire bonding operations of the step (b); and (d) determining the new search height using the wire bonding evaluation criteria monitored during the step (c).
  2. 2 . The method of claim 1 , wherein the new search height is a height of a wire bonding tool above a bonding location prior to entering a constant velocity mode.
  3. 3 . The method of claim 1 , wherein the wire bonding evaluation criteria includes signals monitored during the step (c) and related to at least one of (i) a seek time of a wire bonding tool, (ii) a seek distance of the wire bonding tool, (iii) an impact force of the wire bonding tool, (iv) an impact squash of the wire bonding tool, (v) a z-axis deformation profile, (vi) a bond force oscillation profile, (vii) an ultrasonic impedance characteristic, and (viii) a servo performance of an xyz motion system of a wire bonding machine.
  4. 4 . The method of claim 1 , wherein during the step (d) the new search height is determined to be the same as the search height.
  5. 5 . The method of claim 1 , wherein during the step (d) the new search height is determined to be different from the search height.
  6. 6 . The method of claim 1 , wherein the wire bonding evaluation criteria includes signals related to a seek time of a wire bonding tool, the seek time being a time period between (i) an initiation of seeking contact between the wire bonding tool and a bonding location and (ii) a contact being declared between the wire bonding tool and the bonding location.
  7. 7 . The method of claim 1 , wherein the step (d) includes determining the new search height to ensure that the new search height is low enough to provide a time efficient wire bonding process while providing an acceptable level of the wire bonding evaluation criteria monitored in the step (c).
  8. 8 . The method of claim 1 , where the steps (a)-(d) are repeated for a plurality of iterations, wherein the new search height determined at the step (d) is the search height used in a next of the plurality of iterations.
  9. 9 . The method of claim 1 , where the steps (a)-(d) are repeated for a plurality of iterations until a predetermined criteria is met in consideration of the wire bonding evaluation criteria monitored in the step (c), wherein the new search height determined at the step (d) is the search height used in a next of the plurality of iterations.
  10. 10 . The method of claim 1 , where the steps (a)-(c) are repeated for a plurality of search heights, and wherein the step (d) includes determining the new search height using the wire bonding evaluation criteria monitored during the step (c) for each of the plurality of search heights.
  11. 11 . The method of claim 1 , further comprising a step of (e) determining a blockout time for subsequent wire bonding operations using the new search height determined in the step (d), the blockout time being a time after a wire bonding tool is at the search height in a wire bonding operation but before the wire bonding tool enters a seek mode.
  12. 12 . A method of determining a new blockout time for a wire bonding process, the method comprising steps of: (a) providing a blockout time, wherein the blockout time being a time after a wire bonding tool is at a search height in a wire bonding operation but before the wire bonding tool enters a seek mode; (b) performing a plurality of wire bonding operations using the blockout time; (c) monitoring wire bonding evaluation criteria during each of the plurality of wire bonding operations during the step (b); and (d) determining a new blockout time using the wire bonding evaluation criteria monitored during the step (c).
  13. 13 . The method of claim 12 , further comprising a step of determining a new search height used for subsequent wire bonding operations based on the new blockout time determined in the step (d).
  14. 14 . The method of claim 13 , wherein the step of determining the new search height includes increasing the search height if the new blockout time is longer, and decreasing the search height if the new blockout time is shorter.
  15. 15 . The method of claim 12 , wherein the search height is a height of the wire bonding tool above a bonding location prior to entering a constant velocity mode.
  16. 16 . The method of claim 12 , wherein the wire bonding evaluation criteria includes signals monitored during the step (c) and related to at least one of (i) a seek time of the wire bonding tool, (ii) a seek distance of the wire bonding tool, (iii) an impact force of the wire bonding tool, (iv) an impact squash of the wire bonding tool, (v) a z-axis deformation profile, (vi) a bond force oscillation profile, (vii) an ultrasonic impedance characteristic, and (viii) a servo performance of an xyz motion system of a wire bonding machine.
  17. 17 . The method of claim 12 , wherein the wire bonding evaluation criteria includes signals monitored during the step (c) and related to a servo performance of an xyz motion system of a wire bonding machine.
  18. 18 . The method of claim 12 , wherein during the step (d) the new blockout time is determined to be the same as the blockout time.
  19. 19 . The method of claim 12 , wherein during the step (d) the new blockout time is determined to be different from the blockout time.
  20. 20 . The method of claim 12 , wherein the step (d) includes determining the new blockout time to ensure that the new blockout time is short enough to provide a time efficient wire bonding process while providing an acceptable level of the wire bonding evaluation criteria monitored in the step (c).

Description

CROSS REFERENCE TO RELATED APPLICATION This application claims the benefit of U.S. Provisional Application No. 63/336,227, filed on Apr. 28, 2022, the content of which is herein incorporated by reference. FIELD The invention relates to wire bonding operations, and in particular, to techniques for improving wire bonding operations, for example, in terms of time efficiency. BACKGROUND In the processing and packaging of semiconductor devices, wire bonding continues to be the primary method of providing electrical interconnection between two locations within a package (e.g., between a die pad of a semiconductor die and a lead of a leadframe). More specifically, using a wire bonder (also known as a wire bonding machine), wire loops are formed between respective locations to be electrically interconnected. The primary methods of forming wire loops are ball bonding and wedge bonding. In forming the bonds between (a) the ends of the wire loop and (b) the bond site (e.g., a die pad, a lead, etc.) varying types of bonding energy may be used, including, for example, ultrasonic energy, thermosonic energy, thermocompressive energy, amongst others. Wire bonding machines (e.g., stud bumping machines) are also used to form conductive bumps from portions of wire. In certain applications, the process of forming a wire loop includes positioning a wire bonding tool at a height above a workpiece, and then moving the wire bonding tool to contact the workpiece in connection with a wire bonding operation. The time that elapses between (i) the height above the workpiece, and (ii) the contact with the workpiece, is critical to the efficiency of the wire bonding operation. Thus, it would be desirable to provide improved wire bonding operations, including as related to the timing and efficiency of such operations. SUMMARY According to an exemplary embodiment of the invention, a method of determining a new search height for a wire bonding process is provided. The method includes: (a) providing a search height; (b) performing a plurality of wire bonding operations using the search height; (c) monitoring wire bonding evaluation criteria during each of the plurality of wire bonding operations of step (b); and (d) determining a new search height using the wire bonding evaluation criteria monitored during step (c). According to another exemplary embodiment of the invention, a method of determining a new blockout time for a wire bonding process is provided. The method includes: (a) providing a blockout time, the blockout time being a time after a wire bonding tool is at a search height in a wire bonding operation but before the wire bonding tool enters a seek mode; (b) performing a plurality of wire bonding operations using the blockout time; (c) monitoring wire bonding evaluation criteria during each of the plurality of wire bonding operations during step (b); and (d) determining a new blockout time using the wire bonding evaluation criteria monitored during step (c). The methods of the present invention may also be embodied as an apparatus (e.g., as part of the intelligence of a wire bonding machine), or as computer program instructions on a computer readable carrier (e.g., a computer readable carrier including a wire bonding program used in connection with a wire bonding machine). BRIEF DESCRIPTION OF THE DRAWINGS The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures: FIG. 1 is a timing diagram illustrating points of interest for performing methods in accordance with various exemplary embodiments of the invention; FIGS. 2-4 are flow diagrams for performing various methods of determining a new search height for a wire bonding process in accordance with various exemplary embodiments of the invention; and FIGS. 5-7 are flow diagrams for performing various methods of determining a new blockout time for a wire bonding process in accordance with various exemplary embodiments of the invention. DETAILED DESCRIPTION Exemplary aspects of the invention relate to monitoring signals on a wire bonding system (e.g., a seek time signal, a seek distance signal, an impact force signal, an impact squash signal, etc.) as feedback to automatically adjust (and to improve, and to potentially optimize) a wire bonding tool height. By adjusting the wire bonding tool height (e.g., the search height), performance and efficiency (e.g., UPH, units per hour) of a wire bonding operation may be improved. Further, a communication (e.g., a warning message) may be sent to an operator if the wire bonding tool height (e.g., the search height) is not optimal or has shifted. Further, the monitored seek time (or seek distance) and/or impact force