Flip Chip Solution Using Export
Contents
1. 1 microns OK Cancel AAD HD AAA AAA AAA AAA AAUD SSS RESP PPPS Copyright 2012 by CapeSym Inc All rights reserved www symmic net 5 Open the exported template HBT _FlipChip layout _export xml and it should look similar to the layout but with an additional top layer appended onto the solder bumps as specified On opening this template SYMMIC will ask if you want to save changes to the devices and layout The changes that it is referring to are the default export settings which it wants to update in both the device templates as well as in the layout i e to preserve the export settings just made Select whichever option you prefer Load the new template into SYMMIC and reduce the thickness of the Module layer to 125 Device gt Module Geometry gt Appended Layer Module Thickness Change this layer s material to Copper Device gt Components Module Attach Cu then the template should look like this File Device View Solve Results Settings Help Note that all of the HBT layers are still present as well as all of the heating parameters for each of the HBTs If the template s Boundary Condition section is examined in a plain text editor then a new Film condition will be seen on top of the Module layer The Film conditions on the solder bumps have been removed In addition the SFLUX boundary conditions for the HBTs have been numbered from 1 to 4 using the new dn fl2. Create layout and define a 4 x 1 array starting at 150 500 and spaced at 100 0 with mirroring in X After creating the array complete the layout as shown in the figure below Device Layout Table a M Title Length 500 Width 1000 Meshsize 25s all dimensions in ym Device Device Template File Center at X Position Y Position beg 4 Rotation a 1 Half HBT for a Flip Chi HBT_FlipChip xml a 150 500 mo Noe z 2 Half HBT for a Fip Chi HBT_FlipChip xml a m so 50 _ m None z 3 Half HBT for a Flip Chi HBT_FipChip xml n m 350 50 m r None 4 Hal HBT for a Fip Chi HBTFipchpxm oe o o oe r Ne e 5 Solder Bump for a Flip solderBump_ FlipChip xml l v i50 i50 L E None gt 6 Solder Bump for a Fir solderBump_FipChip xml _ w 150 850 r None gt a ee A e ee A T L M a O S Miana l The completed layout should look as follows Save it as HBT _FlipChip_layout xml Copyright 2012 by CapeSym Inc All rights reserved www symmic net 4 View Solve Results Settings Help E Proje HBT_FlpChp_layout xmi Now export it by selecting File gt Create device template Select the Choose Components to Include button to open the component selection dialog and press the Select All button if not all components are selected Note that the device numbers are shown in the layout when this dialog displays to aid identification
3. a bad mesh and change its description to Width of boundary around the solder bump Find the component called Mesa in the Components folder and rename it to Solder Bump Also change the title of the entire template to Solder Bump for a Flip Chip and delete the help file name Select Device gt Apply then quit and the display will show the updated device Change the bump material to Copyright 2012 by CapeSym Inc All rights reserved www symmic net 2 Solder Device gt Components gt Solder Bump Au80Sn20 and the bump thickness to 500 microns Device gt Thicknesses gt Solder Bump Thickness 500 Finally save this new template as solderBump_FlipChip xml The FlipChip in the name signifies that this template is for Export only as will be explained The next set of changes will be made with a plain text editor e g Notepad TextPad or EditPlus so open the template just saved in your editor of choice Go to the bottom of the file and replace the entire Boundary Conditions section with the following a film on the top of the bump lt BoundaryConditions gt lt Film h P3 temperature P2 face top layer Layer5 toExport 1 extractable true gt lt Blocks x 2 3 y 2 3 gt lt Film gt lt BoundaryConditions gt Next replace the string Z1 Z2 Z3 with 0 in the ZLayers section after which you can safely delete all P43 P45 and P46 Replace Ba
4. ag After creating a template with Export it is always a good idea to check the mesh resolution and adjust it if needed before beginning the solution To do this select Solve gt Model check Show mesh and note the size given in the console window If it needs adjusting the smallest mesh element size in X and Y as well as the bias are given in Device gt Meshing If the equivalent thermal impedance network is desired select that check box in the Solve gt Configure run gt RC calculations dialog then save Now the template is ready to solve select Solve gt Run simulation The solution will take longer if there is more than 1 device and the thermal impedance network is selected Copyright 2012 by CapeSym Inc All rights reserved www symmic net 6 since it must solve everything twice for each device turned on while the others are all off at their off power settings The solution is shown below G Temperature of 4 x 2 HBT Flip Chip Layout Expor File Device View Solve Results Settings Help H N o H a pa N e es Lei 26 85 179 111 C at time Infinity lt The thermal network is stored in two forms in the files with extension BAS and NET If an unsteady network is desired i e an RC network instead of just the R then set up an unsteady run Solve gt Configure run gt Simulation times with very fine steps at the start and that lasts long enough for the devices t
5. apeSym Inc All rights reserved www symmic net 3 As was done for the solder bump template now open this template in your plain text editor of choice Search and replace the string T00 T01 T02 with 0 found in the ZLayers and Boundary Conditions sections after which you can safely delete all three of those parameters T00 TO1 and T02 Finally delete the unused parameters BFT and BFC This completes the template Open the device template in SYMMIC and set up the dimensions materials and powers to those required for the simulation If the layout will use different devices then save each configuration with a unique name Create and Solve the Flip Chip Layout As an example we will solve a chip containing 4 solder bumps and 8 HBT s making use of the chip s symmetry to reduce the problem by half To begin start SYMMIC and load the new solder bump template In Device gt Geometry set the bump Width and Length to 200 and the Boundary Size to 20 In Device gt Thicknesses set the Solder Bump Thickness to 200 as well Save these changes Then load the new HBT template Set it up for 4 fingers Device gt Number of Fingers 4 and enable the Emitter Bus Metal Device gt Optional Parts Set all three bus to boundary values to 2 Device gt Lengths Emitter Bus to Boundary Device gt Widths Base Bus to Boundary Collector Bus to Boundary then save the device Now select File gt
6. ckside BC in the name field of the derived parameters BC1W and BCIL with Template and their descriptions accordingly Change the names of parameters DX and DY to Bump Length and Bump Width respectively and changes their descriptions accordingly then save and exit your editor The template should now be complete Creating a Device Template for Flipping The process for creating a flippable device has similarities to what was done for the solder bump but the boundary condition changes are different In this case the back side boundary condition needs to be removed unless a heat sink will be attached as before but the device heating can stay in place This example will use the generic HBT template but the same procedure could be applied to any device template Open the HBT xml template in SYMMIC then open the Device Template Editor Change the template s title to Half HBT for a Flip Chip From the Edit menu delete the first three layers Edit gt Delete gt Layers layer00 to layer02 Select Device gt Apply to see the model update in the display It should be left with just the Substrate layer matching the solder bump template The Export dialogs now allow the user to specify which components to include so there is no need anymore to explicitly set toExport flags Simply select Device gt Apply then quit and save the modified template as HBT_FlipChip xml Copyright 2012 by C
7. d here begins with a layout of HBT devices and solder bumps These solder bumps are what the chip will be mounted on once it is flipped To create a solder bump template to use in a flip chip layout we begin with a very simple device the Mesa Resistor template A number of changes are necessary many can be done using the Device Template Editor built into SYMMIC whereas all can be done with a plain text editor This note will use a mixture of both approaches To begin start SY MMIC and open the MesaResistor xml template Open the Device Template Editor with File gt Edit device template From the Edit menu delete the first three layers Edit gt Delete gt Layers Layer1l to Layer3 These operations remove the Adhesive Shim and Solder layers leaving just the Substrate and top bump layers If this flip chip will have a heat sink mounted to its back side then don t delete these layers Next find the parameter Z5 Mesa Thickness in the Parameters folder double click the folder to open it and change its min and max values to 1 and 2000 or larger respectively double click the value very slowly then type the new number Change its name to Solder Bump Thickness and its description accordingly For parameters P2 and P3 remove Backside from their names Finally find the parameter Dbound and reduce its min to 1 this value is somewhat arbitrary but it shouldn t be so small as to yield
8. if necessary Choose OK to exit and return to the main dialog Either browse to or type in TypeModule xml into the appended layers box and set it to append lower 1 common layer which will be the Module layer to the top of the device Leave the smallest feature to resolve set at 1 since all components have been retained and no smoothing is necessary then select OK to complete the export The images below show the two export dialogs as described Create Device Template from Layout Choose Components to Include k Save as HBT_FiipChip_layout_export xml ah with device title 4 x 2 HBT Flip Chip Layout Export Select the components to keep in the new device Shared components not shown are kept automatically Select All Clear All Device Component Layer Solder Bump Layers Solder Bump Layers Emitter Bus layer09 Emitter Contact layer09 Emitter Bus layer08 Emitter Cap layer08 Emitter Bus layer07 Base Contact layer07 Emitter layer07 Emitter Bus layer06 Base Bus layer06 Base layer06 Collector Contact layer05 Emitter Bus layer0S Base Bus layer0S Collector layer0S Emitter Bus layer04 Subcollector layer04 Collector Bus layer04 Base Bus layer04 Cancel Append lower 1 common layers from file TypeModule xml mee tothe top or C bottom of the device Layer Component Material Module2 Module Shim CuMoCu Module1 Module Attach In Choose Components to Include Smallest BC feature to retain 1 for all
9. o reach steady state temperatures or nearly so and run again The network files will be updated with the C component In conclusion it bears repeating that a simulation is only as accurate as its boundary conditions In the case of the flip chip this means that accurate temperature boundary conditions for each solder bump or the attached top layer s are essential In many cases it will be necessary to solve the subsystem e g the PCB that the flip chip will mount to first or even concurrently in order to get these temperatures For solutions of the entire subsystem for the purposes of obtaining accurate boundary conditions the details of each HBT are not needed In cases such as these the mesh size and associated computation time can be greatly reduced by not including most or all of the unique components shown in the Choose Components To Include dialog For more information please reference the Creating Device Templates From Layouts section of chapter 4 of the User s Manual which lists a recommended procedure for flip chips Copyright 2012 by CapeSym Inc All rights reserved www symmic net For more information contact Matt Overholt CapeSym Inc 6 Huron Drive Natick MA 01760 USA Email overholt capesym com Tel 1 508 653 7100 x204 Copyright 2012 by CapeSym Inc All rights reserved
10. www symmic net SYMMIC Application Note Flip Chip Solution using Export SYMMIC Template Based Thermal Simulator for Monolithic Microwave Integrated Circuits is a trademark of CapeSym Inc Copyright 2012 by CapeSym Inc All rights reserved www symmic net 1 Flip Chip Solution using Export Flip chips require a slightly different approach for solution than bottom mounted devices due to the different boundary conditions used Typically a layout is used to model a chip and SYMMIC uses linear superposition to solve layouts of devices This method allows very large problems to be solved directly and efficiently i e with matrix inversion instead of iteratively The current implementation version 2 7 0 of this method makes assumptions about the boundary conditions which are unsuitable for flip chip types of analyses so flip chips can only be solved as a single template no layouts This limitation may be removed in a future release but in the mean time the Export feature makes it easy to create the single flip chip template required This application note describes how to configure and export a set of templates for a flip chip type of analysis in two different ways and how to create a flip chip suitable for equivalent thermal impedance network calculation It also highlights some of the power of the Export feature for solutions in general Creating a Solder Bump Template The flip chip example describe
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