Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
1
© John Burke 2006 +1(408) 515 4992
Pitch and PowerPackaging Considerations
Presented by John Burke – Optichron Inc
IEEE CPMT Dinner November 8 2006
© John Burke 2006 +1(408) 515 4992
Background• This paper was prepared as a result of the IEEE
presentation on 40 - 50 micron pitch flip chip bumping a few months ago.
• In 2000 I rationalized that eventually the pitch of a bumped die would start to impact the substrate ability to resolve the interconnection pitch through regular board technology and also start to impact the accuracy/cost of the placement machines used to position the die.
• At that time I applied for a patent through the company that I worked for Saturn Electronics and Engineering for a patent on a traceless flip chip technology for flexible circuit assembly.
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
2
© John Burke 2006 +1(408) 515 4992
Background• More recently I have been considering how to improve
the thermal performance of BGA and similar packages.• Both of these concepts are presented in outline here for
your comments and critique.
© John Burke 2006 +1(408) 515 4992
Traceless flip chip• Having worked on flip chip technology for number of
years – in 2000 I rationalized that if the bumping process got to the level where the pitch was achieving 50 microns pitch or less it would present some sever challenges for the assembly industry in two major areas:
– Placement accuracy– Circuit board production
• The ideas that follow represent the results of the thought process that set out to eliminate both of these issues at finer bumped die pitches.
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
3
© John Burke 2006 +1(408) 515 4992
Conventional trace/pad layoutFlip chip Die
“lollipop” pads
Bumps
© John Burke 2006 +1(408) 515 4992
Traceless trace/”pad” layoutNo pads – solid “picture frame”
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
4
© John Burke 2006 +1(408) 515 4992
Conventional trace/pad theta issue
© John Burke 2006 +1(408) 515 4992
Traceless trace/”pad” theta issue
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
5
© John Burke 2006 +1(408) 515 4992
So you made a short circuit – Big Deal
• So at this point we have an assembly with all die connections shorted together.
• We now have to “find” the die interconnection points which we can only reasonably do – yes you guessed it –by X-ray.
© John Burke 2006 +1(408) 515 4992
Assembly is X ray imaged
We use a real time X-ray to locate the interconnect points between the die bumps and the “picture frame. This is referenced back to fiducials on the flex assembly.
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Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
6
© John Burke 2006 +1(408) 515 4992
Assembly is X ray imaged
Using the co-ordinate data the polyamide is opened and the copper excised using lasers between the traces from the non die side of the flex assembly
© John Burke 2006 +1(408) 515 4992
Conventional trace/pad misaligned
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
7
© John Burke 2006 +1(408) 515 4992
Traceless trace/”pad” misaligned
© John Burke 2006 +1(408) 515 4992
Trials run• In 2000 the only tests that could be run were actually to
open up the polyimide and cut the trace patterns in the copper
• Due to the lack of 40 micron pitch die in 2000 these experiments were actually carried out using regular bump pitches to prove the process.
• Additionally trials were run in slicing the interconnect at a 40 micron pitch using a 3rd party laser service.
• Both trials were successful
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
8
© John Burke 2006 +1(408) 515 4992
Timing• This technology was visualized as a replacement for
TAB in Flex, and as an automated reel to reel process.
• In 2000 it was obvious that it was going to be a technology of the future.
• With the advent of 40 – 50 micron bumping it may be about to mature.
© John Burke 2006 +1(408) 515 4992
Thoughts on BGA Heat Extraction
• Everyone has heard the expression of squeezing a quart into a pint pot. In electronics we are trying in some cases to extract a quart out of a pint pot.
• Thermally that's about where we are at with BGA technology. If you look at the slides on the following pages you can see that all variants of BGA packaging are generally aimed at one thing – getting more heat out of the package.
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
9
© John Burke 2006 +1(408) 515 4992
Conventional BGA packages
© John Burke 2006 +1(408) 515 4992
Conventional BGA packages
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
10
© John Burke 2006 +1(408) 515 4992
So what about a better mouse trap?
• I got to looking at the various solutions and realized that all of the better thermal enhanced packages were either flip chip or mounted bonding side down.
• This is not an issue for your first run unless you may want to FIB the chip……to correct things on the proto’s
© John Burke 2006 +1(408) 515 4992
So what about a better mouse trap?
• I looked around and realized that on the regular less expensive HS – PBGA, XP-FPGA etc. that the main barrier was the molding compound.
• Companies have various solutions to this including dummy silicon sat on top of the die to pipe the heat to the outside heat spreader.
• Unfortunately most of the solutions that involve the use of this type of solution have a rather poor yield since the dummy die has to be incorporated into the assembly during the molding process and this can lead to excessive forces on the active die causing cracking issues.
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
11
© John Burke 2006 +1(408) 515 4992
HE- PBGA Assembly Flow
Base interconnect layerDie
Wire bonds
© John Burke 2006 +1(408) 515 4992
HE- PBGA Assembly Flow
Base interconnect layerDie
Wire bondsHeat Spreader
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
12
© John Burke 2006 +1(408) 515 4992
HE- PBGA Assembly Flow
Injection mold bottom Die set
Injection mold top Die set
Base interconnect layerDie
Wire bondsHeat Spreader
© John Burke 2006 +1(408) 515 4992
HE- PBGA Assembly Flow
Molding compound
Injection mold bottom Die set
Injection mold top Die set
Base interconnect layerDie
Wire bondsHeat Spreader
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
13
© John Burke 2006 +1(408) 515 4992
HTE- PBGA Assembly Flow
Base interconnect layerDie
Wire bonds
© John Burke 2006 +1(408) 515 4992
HTE- PBGA Assembly Flow
Base interconnect layerDie
Wire bondsStepped Heat Spreader
Phase Change Material
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
14
© John Burke 2006 +1(408) 515 4992
HTE- PBGA Assembly Flow
Base interconnect layerDie
Wire bondsStepped Heat SpreaderPhase Change
Material
© John Burke 2006 +1(408) 515 4992
HTE- PBGA Assembly FlowPlastic Injection Inlet
Injection mold bottom Die set
Injection mold top Die set
Base interconnect layerDie
Wire bondsStepped Heat SpreaderPhase Change
Material
Gap
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
15
© John Burke 2006 +1(408) 515 4992
HTE- PBGA Assembly FlowPlastic Injection Inlet
Injection mold bottom Die set
Injection mold top Die set
Base interconnect layerDie
Wire bondsStepped Heat SpreaderPhase Change
Material
© John Burke 2006 +1(408) 515 4992
HTE- PBGA Assembly Flow
Molding compound
Plastic Injection Inlet
Injection mold bottom Die set
Injection mold top Die set
Base interconnect layerDie
Wire bondsStepped Heat
SpreaderPhase Change Material
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
16
© John Burke 2006 +1(408) 515 4992
HTE- PBGA Assembly Flow
Solder Connections
Base interconnect layerDie
Wire bondsStepped Heat
SpreaderPhase Change Material
© John Burke 2006 +1(408) 515 4992
Thought 2
130140150
Go back and take another look at the problem………8-)
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
17
© John Burke 2006 +1(408) 515 4992
Thought 2 process flow…!
Base interconnect layerDie
Wire bonds
© John Burke 2006 +1(408) 515 4992
Thought 2 process flow…!Tooling extension
Compliant material on tool tip
Plastic Injection Inlet
Injection mold bottom Die set
Injection mold top Die set
Base interconnect layerDie
Wire bonds
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
18
© John Burke 2006 +1(408) 515 4992
Thought 2 process flow…!Tooling extension
Compliant material on tool tip
Plastic Injection Inlet
Injection mold bottom Die set
Injection mold top Die set
Base interconnect layerDie
Wire bonds
© John Burke 2006 +1(408) 515 4992
Thought 2 process flow…!Tooling extension
Compliant material on tool tip
Plastic Injection Inlet
Injection mold bottom Die set
Injection mold top Die set
Base interconnect layerDie
Wire bonds
Molding compound
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
19
© John Burke 2006 +1(408) 515 4992
Thought 2 process flow…!
Base interconnect layerDie
Wire bonds
Molding compound
Open cavity after molding process
© John Burke 2006 +1(408) 515 4992
Thought 2 process flow…!
Base interconnect layerDie
Wire bonds
T section Heat-Sprink -radial copper areas with
through holes
Mechanical bond
Thermally conductive compound
Molding compound
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
20
© John Burke 2006 +1(408) 515 4992
Top View Enterprise PackageRadial copper
arms
Through holes to increase air
thermal transfer
Molding compound
Gap on lower side to increase
air flow
© John Burke 2006 +1(408) 515 4992
Enterprise CarrierRadial copper
arms
Through holes to increase air
thermal transfer
Gap on lower side to increase
air flow
Full area Heat-Sprink for maximum transfer
Santa Clara Valley Chapter, CPMT Society
Wednesday, November 8, 2006
21
© John Burke 2006 +1(408) 515 4992
Pitch and PowerPackaging Considerations
Presented by John BurkeIEEE CPMT Dinner November 8 2006
Thank you for your time – Any Questions?