Packages warpage

For the same applied force, the strain on thinner PWBs is higher than that on thick PWBs. Thus, this is more critical on assemblies with relatively thin boards (<93 mils thick). However, depending on the package, warpage, surface finish, and number of test points, it conld also be seen on thick boards. 

JEDEC Standard, JESD22bll2, High Temperature Package Warpage Measurement Methodology, May 2005. www.jedec.org. 

Apart from the electrode warpage and shutdown losses discussed above, certain other technical problems remain to be solved. They include internal leakage, optimization of performance in the low-temperature range, possible startup delays, weight decrease, and packaging capability. It is possible that the bulkiness and weight of this system may limit its potential EV applications to vehicles larger than compact. 

The accuracy of parts is another quality aspect to be considered. Many of the analysis packages promote a better understanding of molding process parameters and the interrelationships between process variables. This contributes to a better ability to control previously mysterious phenomena such as warpage by better process control and cooling system design. 

CR grades are available both as homopolymers and copolymers. Copolymer-based CR grades for injection moulding flow well and are highly resistant to warpage and internal stresses. These grades find application in thin-walled packaging for food and... 

For bolt-down heatsinks, a significant amount of the compressive load comes not from the heatsink weight but from the bolt down mechanism itself. Tolerance variations in package height, warpage, heatsink stand offs, and so on only make the applied load worse. The attachment mechanism should be such that it can accommodate these variations in tolerance without transferring excessive load to the package. 

The thickness of a single piece Ud is typically less than that of the heat spreader/stiffener combination. Changing the stiffness of the package could alter its out-of-plane warpage, which... 

Determine changes in warpage due to package density and location... 

Note that only one-eighth of the package is modeled (Fig. 59.16).This is due to the fact that the package is octant symmetric, and thus symmetry boundary conditions can be employed to reduce the model size, which in turn increases the speed at which a solution can be obtained. Wherever possible, the deformation results of the global FEA model should be verified with experimental warpage measurement (using tools like Shadow Moire ). 

---