Datasheet

LUXEON LED Assembly and Handling Application Brief AB32 20121217 20
3.6 FR4 Board Handling
The substrate of a LUXEON LED is made of ceramic, a relatively brittle material. Even though this product has a small form factor and is unlikely
to cause any problems, forces on the package should be kept to a minimum. In particular, excessive bending forces on the package may crack the
ceramic substrate or break the solder joints.
Figure 25 shows what forces may, inadvertently, be applied to a LUXEON LED when a flat assembled board is bent. This can happen, for example,
when “punching-off” or “breaking-off” LED strips of a PCB panel (Figure 26).
A printed circuit board may warp after reflow when layers with different CTE (coefficient of thermal expansion) are applied to the top and bottom
of the boards. If the PCB is subsequently secured to a flat surface, a vertical force is applied to the ceramic package (see Figure 27). If this force is
large enough, the ceramic substrate package may break. To minimize the chance of cracking the ceramic package, orientate the package such that the
long side of the package is perpendicular to the dominant warpage direction.
Figure 25. Excessive bending force on the PCB may crack the ceramic substrate of a LUXEON LED and/or damage the solder joints.
LED strips
Board panel
Figure 26. PCB panel consisting of several strips of LEDs.
Figure 27. Securing a warped board to flat surface may cause excessive stress on the ceramic substrate.