【正文】 und 板上單個封裝測量的阻尼比很多封裝在板上測量的結(jié)果要低 Factors Affecting Chip Resistances T h e rm a l R e s i s t a n c e v s . A i r V e l oc i t y( 1 2 X 1 2 P B G A )303540451 2 3 4A i r V e l o c i t y , m / sThetaja, C/WTypical Values of qja Pa c k a g eT y p eD i m e n s i o ns(m m )L e a dF r a m eT h e ta ja0 m / sT h e ta ja1 m / sT h e ta ja2 m / s6 4 p i n Q F P 1 4 x 2 0 x 2 . 7 4 2 a l l o y 127 106 991 0 0 p i n Q F P 1 4 x 2 0 x 2 . 7 4 2 a l l o y 102 89 831 6 0 p i n Q F P 2 8 x 2 8 x 3 . 2 C u a l l o y 54 44 461 1 6 p i nF P B G A772 2 4 p i nF P B G A42Source: NEC Packages Typical Values of qja Pa c k a g eT y p eD i m e n s i o ns(m m )L e a dF r a m eT h e ta ja0 m / sT h e ta ja1 m / sT h e ta ja2 m / s2 5 6 p i nP B G A2 7 x 2 7 30 26 243 5 2 p i nA B G A3 5 x 3 5 13 9 75 8 0 p i nA B G A4 5 x 4 5 10 7 52 5 6 p i nT B G A2 7 x 2 7 21 18 165 7 6 p i nT B G A4 0 x 4 0 13 1 0 . 5 9 . 51 2 9 6 p i nF C B G A3 7 . 5 x 3 7 . 5 17 7 6 . 3Source: NEC Packages Typical Values of qja The effect of board configuration on qja q jaB o a r d T y p e N a t u ra lC o n v e c t i o nF o rc e d F l o w ,1 m / sSi n g l e l a y e r b o a r d 52 414 l a y e r b o a r d 24 198 c o m p o n e n ts a t 1 W 5 6 6 2 4 6 4 91 6 c o m p o n e n ts a t 1 W 104 84Source: Motorola Detailed vs Network Models Tcase ~ 7388C Tcase ~ 80C Detailed Model Network Model Rjc=20 Rjb=40 Air velocity = 1 m/s (Rja = 44) (Rja = 40) Exercise 1: PBGA Model 練習(xí) 1： PBGA模型 Exercise 1: PBGA Detailed Model 1. Create a Cabi生成一個 cabi Under Model/Cabi, create a cabi with the following specifications: (All dimensions in m) XS = XE = YS = YE = ZS = ZE = Exercise 1: PBGA Detailed Model 2. Create an Inlet Opening 生成一個入口 Under Model/Openings, create an inlet opening with the following dimensions and velocity specification: Plane: XY XS = XE = YS = YE = ZS = Z velocity = m/s Inlet Opening Exercise 1: PBGA Detailed Model Outlet Opening 3. Create an Outlet Opening 生成一個出口 Under Model/Openings, create an outlet opening with the following dimensions: XS = XE = YS = YE = ZS = Exercise 1: PBGA Detailed Model 4. PCB Material 材料 Under Model/Materials/Solid, create a PCB material with the following specifications: name: pcbmaterial Subtype: other Conductivity: W/mK Toggle on Orthotropic, and assign: X=25 W/mK Y= W/mK Z=25 W/mK Exercise 1: PBGA Detailed Model 5. Create a Plate 生成一塊板 Under Model/Plates, create a plate using the following specifications: (All dimensions in m) Name: pcb Plane: XZ XS = XE = YS = ZS = ZE = Thermal model: Conducting thick Thickness = m Solid material: pcbmaterial Plate creation menu Exercise 1: PBGA Detailed Model 6. Create a detailed PBGA 生成一個詳細(xì)的 PBGA Under Model/Macros/Packages, create a PBGA package: Take all the default specifications as shown in the next four figures with one exception: Change the model type from Compact to Detailed, that is, under Dimensions: Model type: Detailed (See figures in the next four pages) Exercise 1: PBGA Detailed Model PBGA Package creation menu: Dimensions Exercise 1: PBGA Detailed Model PBGA Package creation menu: Substrate Exercise 1: PBGA Detailed Model PBGA Package creation menu: Solder Balls Exercise 1: PBGA Detailed Model PBGA Package creation menu: Die amp。 Mold Exercise 1: PBGA Detailed Model 7. Specify Mesh Controls生成網(wǎng)格 Go to Model/Mesh and specify the following mesh controls: Max X= Max Y = Max Z = Min elements in fluid gap = 2 Min elements on solid edge = 1 Max Ogrid height = 3 Exercise 1: PBGA Detailed Model 8. Get a Solution求解 1. Go to Solution/Solve and click Accept 2. Wait until solution is finished 3. Go to Post and click Object face and select: Object type: group Object name: 4. Toggle on Contours 5. Click Create Exercise 1: PBGA Network Model 9. Create a PBGA Network Model 生成一個 PBGA網(wǎng)絡(luò)模型 1. Make a copy of the PBGA detailed model and name it pbgawork 2. Go to File/Open and load the new model 3. Under Model/Groups, highlight the name and click Delete all。 this deletes all the ponents of the detailed PBGA model Exercise 1: PBGA Network Model 10. Create a PBGA Network Block生成 PBGA塊 2. Under Model/block, create a Network block with the following specifications: (Dimensions in m) XS = XE = YS = YE = ZS = ZE = Rjc = 12 C/W Rjb = 25 C/W Junction power = 1 W Exercise 1: PBGA Network Model 11. Specify Mesh Controls定義網(wǎng)格 Go to Model/Mesh and specify the following mesh controls: Max X= Max Y = Max Z = Min elements in fluid gap = 2 Min elements on solid edge = 1 Max Ogrid height = 3 Max init height = Exercise 1: PBGA Network Model 12. Get a Solution求解 1. Go to Solution/Solve and click Accept 2. Wait until solution is finished 3. Go to Post and click Object face and select: Object type: block Object name: NetworkPBGA 4. Toggle on Contours 5. Click Create Heat Sinks 散熱器 Heat Sinks Heat Sinks ? Heat sinks are used to enhance heat transfer from a ponent by extending the surface area of heat transfer散熱器通過擴(kuò)大散熱面積提高傳熱效果 ? Newton’s law of cooling: Q = h . A . (Tw Tf) Where, Q = total heat transfer from the ponent A = surface area of the ponent Tw = surface temperature of the ponent Tf = surrounding fluid temperature h = heat transfer coefficient ?The above equation states that, for a given Q, h and Tf, the larger the surface area (A), the