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KINTEX-7 FBG (FB) vs. FFG (FF), ARE THEY COMPATIBLE AND WHICH IS BETTER?

Posted by John Pallazola

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Nov 30, 2016 4:41:13 PM

 

Other than a bit of community chatter (much of it contradictory) there is very little easily digestible information on the differences between the Xilinx Flip Chip (FF- LEADED, FFG-LEADFREE) and the Xilinx Lidless Flip Chip (FB-LEADED, FBG-LEADFREE). Xilinx is very good about providing the information needed if you know where to look. We have worked with many OEMs that have used one or the other or both. In this case, you may want to refer to the following Xilinx data sheet and user guide for more details:

 

UG475

DS182

 

Here is a comparison from Avnet showing that the two devices are pin for pin compatible:

product-comparison-page-001-1.jpg

   

XC7K410T-1FBG900I

XC7K410T-1FFG900I

   

Datasheet

Datasheet

 

Kintex-7 FPGA Device-Package Combinations and Maximum I/Os. Devices in FBG900/FBV900 and FFG900/FFV900 are footprint compatible.


kintex-7-fpga-device-package-p.jpg 

In a nutshell, the better performing FF/FFG should almost always work in place of the FB/FBG, but not vice versa. The lidless chip will often work in place of the FF/FFG, but with limited performance, including reduced max speeds and diminished thermal properties. The FF/FFG enables faster transfer speeds, better thermal properties, and less margin for error. The FB/FBG has a slightly lower initial height but once the thermal interface material (TIM) and heatsink is applied that dimension frequently becomes irrelevant.

---------------------------------------------------------------------------------------------------------------------------------

The FB/FBG lidless package requires MANY special considerations and here are a few:

1. Component Pick-up Tool Consideration

For automated pick-and-place machines placing lidless flip-chip BGAs onto PCBs, Xilinx recommends using suction cups or soft tips on the nozzles. Failure to do so will cause chipping, scratching, and cracking of the bare die which can render the chip unusable. This may also lead to failures both immediate or later in the field.

2. TIM (Thermal Interface Material)

Lidless Flip Chips require a layer of thermal interface material between the top of the chip and the heatsink. Because the process of applying this material and the plethora of different materials that can be used it creates another variable that exists even inside a homogenous batch of boards. The upgraded FFG (FF) already has the TIM and heat spreader onboard and built to the exacting Xilinx factory specs, eliminating variables and the concerns of damaging or improperly prepping the FPGA.

3. Heat Sink Guidelines for Lidless Flip-Chip (FB/FBG) Packages

Lidless Flip Chip Concerns:

1. Inconsistent or uneven Force applied.

2. TIM with bond line thickness that is not exactly equal.

3. Even slightly off parallel alignment of the heatsink to the top of silicon will damage and/or destroy the chip.

As you can see, improper heatsink placement onto the die will cause damage and render the lidless chip worthless. 


Here are some of the upgrade/benefits of the FFG/FF: 

1. TIM (Thermal Interface Material) is already resident.

2. Heat spreader lid which has a flat and uniform surface for the attachment of any additional desired heatsink.

3. Superior thermal/heat dissipation properties of the FFG vs the FBG, excerpted here:



 Thermal Resistance Data
thermal-resistance-data-page-0.jpg

  

4. GTX MAX TOP SPEED

Maximum GTX transceiver data Switching rates

FF/FFG packages support up to 12.5Gb/s from the GTX transceivers, nearly 50% more attainable speed than the FB/FBG packages which support data rates up to 6.6 Gb/s. Below is the comparison in the -1 speed which is still a 20% boost from the FF/FFG should you desire to take advantage of it. The config file will determine the actual speed and if you are already using a set speed you like with FBG, you can leave the config file as is and the speed will not change.

GTX Transceiver Switching Characteristics:

gtx-tranceiver-performance-pag.jpg 

In summary, the primary reason to design in the lidless device is perceived cost savings. However, when you factor in the additional, time, labor, fragility, and other special considerations that gap is diminished. Wouldn't it be great if you could get the top of the line FFG/FF with the onboard TIM and heat spreader and all the added benefits for the same price as the FBG, or less? Here is how that can happen:

XC7K410T-1FBG900I Lidless Flip Chip    
Industrial Temp (I) –40°C to +100°C
Avnet screen price:   $1,561
Earthtron's price:      $775 50% Less
 
XC7K410T-1FFG900I Flip Chip
Industrial Temp (I) –40°C to +100°C
Avnet screen price:   $1,952
Earthtron's price:      $755 61% Less
 

 


Earthtron can get discounted price on both packages but typically better on the better-performing FFG parts where Xilinx offers both the FBG (FB) and FFG (FF) package. Contact us for savings on ANY Xilinx part including all of the following devices:
 

XC7K410T-1FFG676C
XC7K410T-1FFG900C
XC7K325T-1FBG676C
XC7K410T-1FBG676C
XC7K325T-2FFG900C
XC7K325T-1FFG676C
XC7K355T-1FFG901C
XC7K325T-2FFG676I
XC7K325T-1FBG900C
XC7K410T-2FFG900I
XC7K325T-1FFG900C
XC7K325T-2FBG676C
XC7K325T-2FFG900I
XC7K410T-1FFG676I
XC7K325T-1FBG676I
XC7K325T-1FBG900I
XC7K325T-2FBG900C
XC7K325T-2FBG676I
XC7K325T-L2FBG676E
XC7K325T-1FFG676I
XC7K325T-2FFG676C
XC7K325T-2FBG900I
XC7K325T-L2FBG900E
XC7K410T-1FBG900C
XC7K325T-3FBG676E
XC7K325T-L2FBG676I
XC7K410T-2FBG676C
XC7K410T-1FBG676I
XC7K325T-1FFV900I
XC7K325T-3FBG900E
XC7K325T-L2FBG900I
XC7K410T-2FBG900C
XC7K325T-L2FFG676I
XC7K355T-1FFG901I
XC7K355T-2FFG901C
XC7K410T-2FFG676C
XC7K410T-2FBG676I
XC7K410T-L2FBG676E
XC7K355T-2FFV901C
XC7K410T-2FBV676I
XC7K410T-2FBG900I
XC7K410T-L2FBG900E
XC7K355T-2FFG901I
XC7K355T-L2FFG901E
XC7K325T-L2FFG900I
XC7K410T-2FFG900C
XC7K410T-3FBG676E
XC7K410T-L2FBG676I
XC7K410T-2FFG676I
XC7K410T-L2FFG676E
XC7K355T-L2FFV901E
XC7K420T-1FFG901C
XC7K410T-2FFV900C
XC7K410T-3FBG900E
XC7K410T-L2FBG900I
XC7K355T-3FFG901E
XC7K355T-L2FFG901I
XC7K410T-L2FFG900E
XC7K410T-3FFG676E
XC7K410T-L2FFG676I
XC7K420T-1FFG1156C
XC7K420T-2FFG901C
XC7K420T-1FFG901I
XC7K410T-3FFG900E
XC7K410T-L2FFG900I
XC7K420T-2FFG1156C
XC7K420T-1FFG1156I
XC7K480T-1FFG901I
XC7K480T-2FFG901C
XC7K420T-2FFG901I
XC7K420T-L2FFG901E
XC7K420T-L2FFV901E
XC7K480T-1FFG1156I
XC7K480T-2FFG1156C
XC7K420T-2FFG1156I
XC7K420T-L2FFG1156E
XC7K480T-2FFG901I
XC7K480T-L2FFG901E
XC7K420T-3FFG901E
XC7K420T-L2FFG901I
XC7K480T-2FFV1156C
XC7K480T-2FFG1156I
XC7K480T-L2FFG1156E
XC7K420T-3FFG1156E
XC7K420T-L2FFG1156I
XC7K480T-3FFG901E
XC7K480T-L2FFG901I
XC7K480T-2FFV1156I
XC7K480T-3FFG1156E
XC7K480T-L2FFG1156I
XC7K480T-3FFV1156E
XC7K325T-1FFG900I
XC7K325T-3FFG676E
XC7K325T-L2FFG676E
XC7K325T-L2FFG900E
XC7K480T-1FFG1156C
XC7K480T-1FFG901C
XC7K410T-1FFG900I

Contact EarthTron LLC to Buy Xilinx FPGA 
Call us: 1-800-322-2130
 

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EarthTron LLC is an Unlimited Franchised Distributor of Electronic Components and Products. We provide customers with services not available from a restricted Franchised Distributor. In addition to our franchised lines we give you the convenience of only having to go to one company for ALL of your electronic component needs. This saves you the time of having to contact multiple companies for every part that you need. Our experience in the industry gives you the confidence that we only source from quality suppliers, to deliver quality parts. Buy Xilinx FPGA and save off of distributor pricing! 

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Topics: xilinx, FPGA

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