Study Of Delamination On Leadframe Paddle In QFN Package

Packaging is the last process to realize chip performance. Rapid development of information technology asks more and more high reliability requirements on products. In the case of QFN(Qual Flat Non Lead), it is important to solve delamination problem to prolong product lifetime.This thesis focuses on real delam phenomenones frequently happened on leadframe paddle top surface. On the basis of microscopic appearance of delam, conducting 32 DOE(Design of Experiment) groups, the following results are drawn:(1) Using epoxy instead of DAF(Die Attach Film), to adopt groove design and performing BO(Brownification Oxidation) treatment, can reduce or even eliminate the delam happened on top paddle.The corresponding key parameters in consideration are: elastic modulus & CTE(Coefficient of Thermal Expansion), adhesive area, and adhesive strength.(2) To reduce half etching area on leadframe paddle bottom surface, performing BO treatment can reduce or even eliminate the delam happened on paddle bottom surface.The corresponding key parameters in consideration are: filling gap, adhesive strength.(3) To change leadframe taping mode and to reduce thermal expansion of plastic resin, both have no any effect on delam results.(4) Using epoxy instead of DAF, the limitation is on chip stacking layer; To adopt groove design, the limitation is on die size; To reduce half etching area, the limitation is on customer E-pad design. But BO treatment can fit any condition.To draw conclusions all in all, material properties(elastic modulus, CTE), leadframe design(filling gap, adhesive area), and BO(adhesive strength) are the three important solutions to delam problems; Reasonable allocation among them are needed for different delam phenomenons, different packing structure and customer quality may be required.