Means for measuring coplanarity of leads on an IC package

• US 5,249,239 A
• Filed: 07/15/1991
• Issued: 09/28/1993
• Est. Priority Date: 07/17/1990
• Status: Expired due to Term

• Current Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Original Assignee: NEC Corporation
• Inventors: Kida, Tomoyuki
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): Johns, Andrew W.
• Application Number:
  US07/729,921
• Time in Patent Office: 806 Days
• Field of Search: 382/8, 382/44, 382/47, 358/101, 358/106, 358/107, 359/668, 359/669, 359/670, 359/710, 356/237
• US Class Current: 382/146
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 5/80 Geometric correction
• CPC Class Codes: G06T 7/0006 using a design-rule based approach
• CPC Class Codes: G06V 10/12 Details of acquisition arrangements; Constructional details thereof

Abstract

A coplanarity measuring apparatus includes an image converting section, an optical lens mechanism, an image processing section, and an arithmetic operating section. The image converting section converts a transmission image of lead end portions of a surface-mount type IC package into image data. The optical lens mechanism vertically enlarges a transmission image, of the lead end portions, which is projected by the image converting section, and horizontally reduces the vertically enlarged transmission image. The image processing section converts the image data output from the image converting section into binary data and forming a profile. The arithmetic operating section calculates a coplanarity from the profile formed by the image processing section and checks whether a product is defective.

Claims

1. A coplanarity measuring apparatus comprising:

image converting means for converting a transmission image of lead end portions of a surface-mount type IC package into image data;

an optical lens mechanism, for vertically enlarging a transmission image, of the lead end portions, which is projected by said image converting means, and horizontally reducing the vertically enlarged transmission image;

said optical lens mechanism comprising a vertical component enlarging cylindrical lens and a horizontal component reducing cylindrical lens;

image processing means for converting the image data output from said image converting means into binary data and forming a profile;

arithmetic operating means for calculating a coplanarity from the profile formed by said image processing means and checking whether a product is defective; and

curvature correction means comprising a data table having stored therein correction values for errors based on the curvatures of said cylindrical lenses, with a calculated result of coplanarity being used as an index, and said arithmetic operating means for calculating a preliminary coplanarity from the formed profile, and from said curvature correction data table for obtaining a correct coplanarity.

2. An apparatus according to claim 1, further comprising curvature correction data forming means for obtaining correction values for the errors by actual measurement, and registering the correction values in said curvature correction data table.

3. An apparatus according to claim 1, wherein said image processing means comprises a binary operating section for converting multi-valued data of a fetched transmission image into binary data in accordance with a threshold level registered in advance, and a profile forming section for forming a vertical profile by vertically accumulating bright points, of the binary data, which respectively represent float amounts of lead end portions.

4. An apparatus according to claim 1, wherein said arithmetic operating means comprises a coplanarity calculating section for calculating float amounts of the respective lead portions on the basis of a vertical profile from said image processing section, retrieving a maximum value from the float amounts, and obtaining a coplanarity on the basis of the retrieved maximum value, and a GO-NG determining section for comprising the obtained coplanarity with a standard value registered in advance to check whether the product is defective.

5. An apparatus according to claim 4, wherein said arithmetic operating means comprises a calibration section for calculating a resolution used to convert measurement data arranged in units of pixels into data in μ

m, and said complanarity calculating section obtains a coplanarity by multiplying the retrieved maximum value by the resolution.

6. An apparatus according to claim 1, wherein said image converting means and said optical lens mechanism are arranged along each of four sides of the IC package.

7. A coplanarity measuring apparatus characterized by comprising:

image converting means for converting a transmission image of lead end portions of a surface-mount type IC package into image data;

an optical lens mechansim, for vertically enlarging a transmission image, of the lead end portions, which is projected by said image converting means, and horizontally reducing the vertically enlarged transmission image;

said optical lens mechansim comprises a vertical component enlarging cylindrical lens and a horizontal component reducing cylindrical lens;

image processing means for converting the image data output from said image converting means into binary data and forming a profile;

said image processing means comprising a binary operating section for converting multi-valued data of a fetched transmission image into binary data in accordance with a threshold level which is registered in advance, and a profile forming section for forming a vertical profile by vertically accumulating bright points, of the binary data, which respectively represent float amounts of lead end portions;

arithmetic operating means for calculating a coplanarity from the profile formed by said image processing means and checking whether a product is defective;

a curvature correction means including a data table having stored therein correction values for errors based on the curvatures of said cylindrical lenses, with a calculated result of coplanarity being used as an index, and said arithmetic operating means for calculating a preliminary coplanarity from the formed profile, and from said curvature correction data table for obtaining a correct coplanarity;

said arithmetic operating means further comprising a coplanarity calculating section for calculating float amounts of the respective lead portions on the basis of a vertical profile from said image processing section, retrieving a maximum value from the float amounts, and obtaining a coplanarity on the basis of the retrieved maximum value, and a GO-NO/GO determining section from comparing the obtained coplanarity with a standard value registered in advance to check whether the product is defective;

said arithmetic operating means further comprising a calibration section for calculating a resolution which is used to convert measurement data arranged in units of pixels into data in μ

m, and said coplanarity calculating section obtains a coplanarity by multiplying the retrieved maximum value by the resolution.