Dc/dc convertor power module package incorporating a stacked controller and construction methodology

Abstract

Methods and systems are described for enabling the efficient fabrication of small form factor power converters and also the small form factor power converter devices.

1 . A power converter package comprising,
 a lead frame having a first die attach pad, a second die attach pad, and a plurality of leads including a switch node that comprise at least one of the plurality of leads;   a high side (HS) field effect transistor (FET), the HS FET includes a source contact and gate contact arranged on a face surface of the HS FET and a drain contact on a bottom surface of the HS FET and the bottom surface of HS FET is mounted facing toward the lead frame and the drain of the HS FET is coupled with the first die attach pad;   a low side (LS) field effect transistor (FET), the LS FET includes a source contact and gate contact arranged on a face surface of the LS FET and a drain contact on a bottom surface of the LS FET and the facing surface of LS FET is mounted facing toward the lead frame with the source of the LS FET coupled with the second die attach pad;   an electrically conductive clip that electrically connects with the source of the HS FET and the drain of the LS FET and a lead frame switch node, wherein the switch node comprises at least one of the plurality of leads of the lead frame, thereby defining a switch connection for the power converter package at least one of the leads to form a switch connection, wherein the electrically conductive clip electrically connects the HS FET and the LS FET using a bottom surface of the of the electrically conductive clip; and   a controller device mounted with the clip and arranged above the HS FET and the LS FET and electrically connected with the HS FET and the LS FET.   
     
     
         2 . (canceled) 
     
     
         3 . The power converter package recited in  claim 1 , wherein
 the electrically conductive clip electrically connects the source of the HS FET and the drain of the LS FET to establish an electrical connection between the HS FET and the LS FET and said switch node to form the switch connection.   
     
     
         4 . The power converter package recited in  claim 3 , wherein the controller is nonconductively mounted on the second surface of the electrically conductive clip and wherein the controller is electrically connected with the gate contacts of the HS FET and the LS FET. 
     
     
         5 . The power converter package recited in  claim 4 , wherein
 the controller is electrically connected with the gate contact of the HS FET with a wire bond; and   the controller is electrically connected with the gate contact of the LS FET with a wire bond.   
     
     
         6 . A power converter package comprising,
 a lead frame having a die attach pad and a plurality of leads;   a low side field effect transistor (LS FET) comprising a gate contact and a source contact arranged on a facing surface of the LS FET and a drain contact on a bottom surface of the LS FET, the LS FET further arranged on the die attach pad such that the source contact of the LS FET is electrically coupled with the first die attach pad such that the LS FET gate contact is electrically coupled with at least one of said plurality of leads;   a conductive clip arranged above the LS FET to enable electrical connection between a drain contact of the LS FET and the clip;   an interposer element arranged on the clip and configured to reorient gate contacts of high side field effect transistor (HS FET) mounted thereon;   the HS FET is arranged on the clip such that an electrical contact passes through a conductive channel of the interposer enabling a current path between the HS FET source and the clip and such that a gate tab of the interposer connects with a gate of the HS FET wherein the gate tab presents a good wire bonding surface; and   a controller mounted on the lead frame proximal to the LS FET and electrically connected with the HS FET and the LS FET.   
     
     
         7 . The power converter package recited in  claim 6 ,
 wherein the HS FET includes a source contact and gate contact arranged on a facing surface of the HS FET and a drain contact on a bottom surface of the HS FET;   wherein the clip has a first surface and an opposing second surface;   wherein the interposer element is arranged on the first surface of the clip;   the LS FET is arranged on the second surface of the clip;   wherein the HS FET facing surface is oriented toward the interposer enabling the interposer to reorient the gate contacts of HS FET to be exposed from above presenting suitable wire bonding surface; and   wherein the channel of the interposer enables the HS FET source contact to electrically connect with the clip and therethrough connect with the drain contact of the LS FET to form a switch connection between the LS FET and the HS FET.   
     
     
         8 . The power converter package recited in  claim 7  wherein,
 the conductive tab of interposer element is formed on upper portion of the interposer element does not penetrate all the way through the interposer element. 
 
     
     
         9 . The power converter package recited in  claim 8  wherein, the conductive gate tab of the interposer element is electrically coupled with the gate contact of the HS FET and extends beyond an outer periphery of the HS FET to expose a top surface of the gate tab forming a gate bond pad for the HS FET. 
     
     
         10 . The power converter package recited in  claim 9  wherein, the controller is wired bonded to the HS FET using the gate tab of the interposer element. 
     
     
         11 . A method of forming a power converter package, the method comprising, electrically coupling a HS PET and a LS PET to die attach pads of a lead frame;
 electrically coupling a first side of a conductive clip to a drain of the LS PET and a source of the HS PET to form a switch connection such that a portion of the clip is also electrically coupled with a switch node of the lead frame;   non-conductively coupling a controller with a second side of the clip;   wire bonding the connecting gates of the HS PET and LS PET with the controller;   encapsulating the power converter package; and   singulating the encapsulated package to form a completed power converter package.   
     
     
         12 . The method of  claim 11  further including mounting a power connector such that it is electrically coupled with a Vin node of the lead frame and is arranged to provide power the power converter package. 
     
     
         13 . The method of  claim 11  wherein said coupling the first side of the first clip to a drain of the LS PET and non-conductively coupling the controller with a second side of the first clip includes a flip chip type process wherein a first one of the LS PET and the controller is coupled with the clip which is then flipped over and then another one of the LS PET and the controller is coupled with the first clip. 
     
     
         14 . The method of  claim 11  wherein said coupling of the LS PET and the HS PET to the lead frame is conducted prior to the attachment of the clip. 
     
     
         15 . The method of  claim 14  wherein said lead frame comprises a preformed lead frame. 
     
     
         16 . A method of forming a power converter package, the method comprising, electrically coupling a LS PET to a die attach pad of a lead frame; non-conductively coupling a controller to the lead frame;
 electrically coupling a first side of a clip to a drain of the LS FET and to a switch node of the lead frame;   arranging an interposer element on a second side of the clip, the interposer element having a gate tab and a conductive channel that passes through the interposer element that is electrically coupled with the drain of the LS FET;   arranging a HS FET on the interposer such that a source of the HS FET is electrically coupled with the drain of the LS FET through the channel such that the HS FET source, the HS FET drain, and the switch node are electrically coupled via the clip to form a switch connection;   wherein said arranging of the HS FET on the interposer further includes arranging the HS FET such that HS FET gate is electrically coupled with the gate tab such that the gate tab extends beyond an outer periphery of the HS FET to present a gate bonding surface;   electrically connecting gates of the HS FET and LS FET with the controller using at least wire bonding to the controller;   encapsulating the power converter package; and singulating the encapsulated package to form a completed power converter package.   
     
     
         17 . The method of  claim 16  further including mounting a power connector such that it is electrically coupled with a Vin node of the lead frame and is arranged to provide power to converter package. 
     
     
         18 . The method of  claim 16  wherein said coupling of the LS FET and the controller to the lead frame is conducted prior to the attachment of the first clip. 
     
     
         19 . The method of  claim 16  wherein said lead frame comprises a preformed lead frame. 
     
     
         20 . The method of  claim 16  wherein arranging said HS FET on the interposer 
       element comprises attaching the HS FET to the interposer element to form an 
       interposer sub-assembly which is mounted with the clip as a unit. 
     
     
         21 . The method of  claim 20  wherein,
 the LS PET, the lead frame, and the first clip are assembled to form a lead frame sub-assembly; 
 the lead frame sub-assembly is coupled with the interposer sub-assembly. 
 
     
     
         22 . The method of  claim 16  wherein a power connector is mounted and arranged above the HS PET and electrically coupled with a Yin lead of the lead frame and is electrically coupled with at least the HS PET. 
     
     
         23 . An interposer apparatus for use with a field effect transistor (PET) device, the apparatus comprising,
 an interposer body having a first surface and a second surface with an interposer core sandwiched between the first surface and the second surface;   a conductive channel arranged such that it has a first conductive contact on the first surface of the body and a second conductive contact on the second surface of the body with a conduction path that passes through the core electrically connecting the first conductive contact with second conductive contact;   an electrical gate tab with an electrical contact surface at the first surface of the of the interposer; and   the apparatus configured to enable coupling with a PET device so that when mounted, a PET source electrically couples with the first conductive contact of the conductive channel at the first surface of the interposer and so that the PET gate electrically couples with the gate tab at the first surface of the interposer, and wherein the gate tab extends beyond an outer periphery of the mounted PET so that a portion of the tab is exposed on the first surface of the interposer thereby enabling the wire bonding to a PET drain and the gate tab on a same side of the interposer.