IE980650A1

IE980650A1 - Solder paste measurements

Info

Publication number: IE980650A1
Application number: IE980650A
Authority: IE
Inventors: James Mahon Sean O' Kootsookos; Mahon James; O'neill Sean; Conlon Peter; Peter Kootsookos
Original assignee: M V Res Ltd
Priority date: 1998-02-09
Filing date: 1998-08-04
Publication date: 1999-08-11
Also published as: JPH11316109A

Abstract

PROBLEM TO BE SOLVED: To provide a measuring system of solder paste which determines the position and volume of the individual solder deposit easily, rapidly, and efficiently in a manner adapted to the fast manufacturing environment. SOLUTION: A solder deposit on a substrate is measured by means of a camera 41 to determine the two-dimensional position of the bump. The image from the camera 41 is processed at fast while the substrate is illuminated by an axially-illuminating LED group 42. This results in easy filtering of a bare pad portion. After the two-dimensional inspection, a gantry head is moved by means of a laser 44 and a laser sensor 46 to measure the height and volume of the selected solder deposit. The laser 44 illuminates a beam 60 in a form of a sheet of light directed to the substrate as a straight line at an angle of 45 deg. with respect to the x-axis and y-axis of the substrate. Since the beam 60 has a certain angle with respect to the vertical direction, the deposit causes unevenness on the line caught by the camera 46. The level of this unevenness shows the height of the bump.

Description

Solder Paste Measurement Solder bumps on a substrate are measured by initially using a camera (41) to determine two dimensional location of the bumps. Images from the camera (41) are processed firstly when the substrate is illuminated by upper LEDs (421) providing on - axis illumination. This allows simple filtering out of the bare parts of pads. While the gantry head is at simple illumination of the substrate. After two - dimensional inspection, the gantry head is moved for volume measurement of selected solder bumps using a laser device (44) and a laser sensor (46). The laser device (44) emits a beam (60) in the form of a sheet of light which impinges on the substrate as a line. Because the beam (60) is at an angle to the vertical, the bumps cause an irregularity in the line as used by the camera (46). The extent of the irregularity indicates the bump height.

Claims

1. A solder bump measurement system (1) comprising means of supporting a target substrate (50) with solder bumps (51), a light source (44) mounted to direct a beam of light at the target, a camera (45) mounted to receive reflected light, and an image processor (6) connected to the camera and comprising means for digitising received light signals and analysing the resultant digital signals to determine solder bump height data, characterised in that, the light source (44) emits a sheet (60) of light which impinges on the target as a line (116), and the camera (45) and the light source (44) are mounted at an angle with respect to each other whereby differences in height at which the beam impinges on the target are represented as a pattern (116) in the line as viewed by the camera.

2. A solder bump measurement system as claimed in claim 1, wherein the camera (45) and the light source are mounted so that the camera is vertically above the location at which the light beam impinges on the target.

3. A solder bump measurement system as claimed in claims 1 or 2, wherein the camera and the light source are co-planar and are at a mutual angle in the range of 15° to 25°.

4. A solder bump measurement system as claimed in claim 3, wherein the angle is approximately 20°.

5. A solder bump measurement system as claimed in any preceding claim, wherein the sheet of light impinges on the substrate at an angle of -12approximately 45° to both orthogonal directions of orientation of the solder blobs.

6. A solder bump measurement system as claimed in any preceding claim, wherein the image processor comprises means for representing each line of light as a row of pixels (71), the intensity of each pixel being proportional to the extent of deviation of the corresponding light.

7. A solder bump measurement system as claimed in any preceding claim, wherein the system comprises a gantry (4), and the camera and the light source are mounted on a gantry head, and the gantry further comprises a drive means (30, 33) for moving the head to selected target regions and to step drive the head to a series of successive discrete positions within the target region.

8. A solder bump measurement systems as claimed in any preceding claim, wherein the image processor (6) comprises means for filtering received digital light signals using median filtering techniques to eliminate pixel outliners.

9. A solder bump measurement systems as claimed in any preceding claim, wherein the system initially performs (101) a two-dimensional inspection of the target to determine the location of solder bumps to be measured.

10. A solder bump measurement systems as claimed in claim 9, wherein the system comprises a vertically-mounted camera, a light source for emitting onaxis beams and a light source for emitting off-axis beams, and the image processor comprises:means for switching the light sources, and -13means in the image processor for processing light signals reflected from the on-axis beams to eliminate bare pads, and for processing reflected light from off-axis beams to eliminate a substrate. 5

11. A solder bump measurement systems as claimed in claims 9 or 10, wherein the light sources (42, 43) are light emitting diodes and are arranged in rings symmetrically around the camera. 1 / 8