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Browse Prior Art Database

IMPROVED SOLDERING TECHNIQUE FOR SURFACE MOUNTED RF POWER DEVICES

IP.com Disclosure Number: IPCOM000006048D
Original Publication Date: 2001-Nov-28
Included in the Prior Art Database: 2001-Nov-28
Document File: 2 page(s) / 34K

Publishing Venue

Motorola

Related People

Dan J. Buntley: AUTHOR [+2]

Abstract

IMPROVED SOLDERING TECHNIQUE FOR SURFACE MOUNTED RF POWER DEVICES

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IMPROVED SOLDERING TECHNIQUE FOR SURFACE MOUNTED RF POWER DEVICES

By Dan J. Buntley and Brian Breunig

 
 

It is common in the electronics industry that RF power devices are mounted in close proximity to some form of heat spreading source usually with a good thermal conductor between the two to ensure consistent, long term heat spreading capability. The mounting techniques vary from mechanically fastening the power device to the heat spreader, which typically uses thermal grease as the interstitial layer, or the power device is soldered to the heat spreader directly.  There is a growing trend in the packing of RF power devices, however, that presents unique challenges to thermally managing these components. Surface mount style packaging of power devices is not new.  However, the smaller these power devices become along with the higher power requirements needed for the applications both provide difficult obstacles to overcome when using these surface mount devices in today’s electronics.

Figure 1: Solder prior to reflow in non-plated thru holes in PCB and close up of hole feature.


 These surface mount power devices are typically mounted on the surface of a printed circuit board on top of a bed of vias.  A heat-spreading medium usually exists underneath the circuit board and is attached using a thermally conductive compound prior to the population of the power devices.  The majority of the heat created by the power device travels down the copper barrels of the vias, through the thermally conductive compound, and then is dissipated by the heat spreader. It would be advantageous to have these vias filled with a material that is as conductive as the vias to maximize the heat that can be removed from the device. However, many of the conductive compounds used today do not

perform nearly as well as copper.  Although solder is not as conductive as copper, solder is the next best alterative due to its available during the population of the components on the circuit board. 

The crux of the problem is how to create a solder connection between the power device, the heat spreader and the circuit board if the heat spreader and Printed Circuit Board (PCB) are already attached to each other prior PCB population. The following describes a unique soldering technique that achieves the desired result of an improved thermal path for surface mounted power devices.

There are two key features that allow this technique ...