October, 2023 Continued from page 62
tive and displays a geometry-calibrated image. This makes it easier to evaluate the voids and improves the accuracy of the meas- urement. It also speeds up the creation of the inspection program. A uniform component library can be used to create the program. In addition to void percentage, area of the
voids in square millimeters, number of voids, largest void, etc., are also reported. Presence, position and rotation are checked. It is tested for short circuits and the insulation distance between the LED solder joints is determined. Solder balls located between the solder joints are detected even though they do not yet rep- resent a short circuit. In addition, solder balls in the direct vicinity of the LED are detected.
Not All 3D is the Same A 3D X-ray image is calculat-
ed from several oblique X-ray images (so-called projections). The number of oblique images used for a 3D image reconstruction is a measure of the quality of the 3D slice image. The more oblique images are used, the “better” the 3D image. For LEDs, GÖPEL elec- tronic typically uses between 8
A 3D X-ray image is calcu- lated from several oblique X-ray images (so-called
projections). The number of oblique images used for a
3D image reconstruction is a measure of the quality of the 3D slice image.
and 16 projections at a resolution between 10 and 15 µm/pixel. This is where a weakness of
the conventional stop-and-go image recording technique be - comes apparent. For 3D image capture, a flat-panel detector is moved along a circular path to capture the individual oblique images. Each position must be approached individually. This costs time and results in long inspection cycles. For this reason, such systems usually use simple 2D and 2.5D images to evaluate the LED solder joints. But due to vias under the LEDs and the inner LED structure itself, only a limit- ed evaluation is possible this way. The MultiAngle Detector 3 of
the X Line — 3D does not rely on stop-and-go image acquisition with flat-panel detectors. This detector enables scanning 3D X- ray image acquisition. The oblique radiographic images are acquired by several digital line detectors in parallel directly in motion. The number of oblique projections for the 3D calculation can be freely selected. This way, short inspec- tion times can be guaranteed. The MultiAngle Detector 3
can also inspect in 2D in simple situations without overlaps. Another advantage results from the fact that LED boards are often designed for multiple use. Thus, several PCBs are contained in one scan strip. All components that are in the scan strip can be tested
www.us -
tech.com 3D X-ray inspection of LEDs for vehicle headlights
without affecting the cycle time. With the X Line — 3D, LEDs can be X-
rayed in a series cycle by means of a fast, scan- ning 2D or 3D X-ray image acquisition. The quality of the 3D image is scalable and can be
adapted to the required cycle time. The advan- tage of 3D inspection lies in the suppression of interfering structures due to vias and the internal structure of the LED, and in the geo- metrically calibrated imaging of the LED sol- der joints. This provides more precise meas- urement of air inclusions. This 100% inline inspection ensures the quality of LED PCB, guaranteeing their service life and preventing failures in the field. Contact: GÖPEL electronic GmbH,
Göschwitzer Street 58/60, 07745 Jena, Germany % +49-0-3641-6896-739 E-mail:
presse@goepel.com Web:
www.goepel.com r
3D X-ray image (left) and 3D visualiza- tion with topoVIEW (right).
See at productronica, Hall A2 Booth 239
Page 65
See at productronica, Hall A2 Booth 413
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