AB136 LUXEON MZ Application Brief 20150528 ©2015 Lumileds Holding B.V. All rights reserved.

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4.4 Thermal Measurement Result

A 1.6mm thick Al-MCPCB star board with 1 oz top copper, dielectric thickness of 0.08mm and dielectric thermal

(Rq

For other PCB designs, an experiment or thermal simulation may need to be conducted to determine (Rq

T

5. Assembly Process Guidelines

5.1 Stencil Design

Figure 14 shows the recommended stencil design for LUXEON MZ. The recommended stencil thickness is 125μm.

Figure 14. Recommended stencil design for LUXEON MZ. All dimensions in mm.

5.2 Solder Paste

Lumileds recommends a lead-free no clean solder paste to mount LUXEON MZ emitters onto a PCB. Lumileds successfully

tested a solder paste from Alpha® SAC305-CVP390-M20 type 3. However, since application environments vary widely,

Lumileds recommends that customers perform their own solder paste evaluation in order to ensure it is suitable for the

targeted application.

5.3 Solder Paste Screen Printing

In general there are three methods to align the stencil to the PCB during solder paste screen printing:

1. The stencil is manually aligned to the PCB prior to printing. No adjustments are made during printing.

2. The stencil is manually aligned to the PCB prior to printing. During printing, the machine keeps track of the PCB

fiducial mark(s) and makes any necessary adjustments to maintain proper alignment with the PCB.

3. A technician performs a crude alignment of the stencil to the PCB. During printing, the machine keeps track of

the PCB fiducial mark(s) and the stencil fiducial mark(s) and maintains proper alignment between the fiducials

throughout the process.

Method 1 has the worst accuracy and repeatability of the three methods discussed. Method 2 offers the same accuracy

as method 1 but ensures better repeatability. Method 3 has the best accuracy and best repeatability of the 3 methods

discussed.