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LCP Sample Package Results Improves Modelling Confidence

Figure 1 Figure 2

Figures 1 and 2

Overview

Labtech Microwave in the summer of 2008 provided QFN style 5mm x 5mm demonstrator packages using liquid crystal polymer (LCP) material. The sample pack included an open cavity package for mounting an active device and a closed package with a continuous through line for characterisation. The open package is shown in figures 1 and 2 above. The sample pack also included a motherboard made from Rogers RO3003 material with RFOW probe pads to enable the package to be measured in a representative environment. This note presents the measured data for the through line along with an analysis of that data.

Summary

The measured data shows excellent performance to 20GHz; with an insertion loss of around 1.5dB and a return loss better than 15dB for the whole assembly. Analysis and de-embedding of the data shows the performance extending to beyond 30GHz and shows the insertion loss of each RF package transition to be around 0.1dB at 20GHz. Predictions for the package using an improved motherboard layout would extend the performance to 40GHz.

Measured Data

The data in figure 3 is for a through line in LCP mounted to a RO3003 motherboard shown in figures 4 and 5 below. The measurement was made using an Anritsu Universal Test Fixture using 'V' connectors and Anritsu VNA 37397A. The insertion loss in cyan squares is shown on the right hand scale. The return losses in blue triangles and brown diamonds, the input and output respectively, are shown on the left hand scale.

The insertion loss measured is initially a little disappointing at 1.5dB at 20GHz; however the return losses are good at nearly 15dB to 20GHz. The motherboard feed lines at approximately 8mm each side and the 3.5mm length of line inside the package contribute significantly to the overall loss.

The very sharp increase in insertion loss, 12dB, centred at 39GHz is predictable and is shown in a later section to be caused by the layout of the motherboard and is not characteristic of the package.

Figure 3

Figure 3

Figure 4

Figure 4

Figure 5

Figure 5

Measured and Modelled Data

Figures 6 and 7 show a comparison between the measured and the simulated data for the package and test board assembly. Figure 6 shows the input return loss for the measurement in dashed red and the simulation in solid blue. The data fits very well to beyond 40GHz. Figure 7 similarly shows the data for the insertion loss.

Figure 6

Figure 6

Figure 7

Figure 7

 

Continued:

Contacts:

Labtech Microwave
Broadaxe Business Park
Presteigne
Powys
LD8 2UH
UK

Steve Melvin
Principal Engineer

Tel: +44 (0) 1908 267611 (Direct)
Tel: +44 (0) 1908 261755 (Switchboard)
Fax: +44 (0) 1908 261788
Email: s.melvin@labtech.ltd.uk

www.labtechmicrowave.com

Disclaimer:
Whilst Labtech Microwave makes every effort to ensure that information contained in this document is accurate and correct, the information should not be relied upon and Labtech Microwave does not warrant the accuracy of the content and does not accept any responsibility for any use made of this information.

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