Problems of tests conducting of microcircuits in BGA-type metal-polymeric packages
Instrument production techniques
Аuthors*, **, ***
Scientific Research Institute of System Analysis, 36/1, Nakhimovsky av., Moscow, 117218, Russia
The article focuses on the problems related to a special purpose chipping in metal-polymeric packages with ball leads of the BGA-type (Ball grid array). During microcircuits’ burn-in test and functional control within the specified temperature range a lot of cases of the ball leads separation occurred. This separation led to the need to discard the operable ICs at the final phase of testing. Furthermore, the separation was occurring during the transportation of products.
The author analyzed the reasons for strength decline of the leads on various production and testing stages. The method for minimization of the the leads’ strength reduction was worked out. Moreover, the sound arguments are presented in favor of moving the ball-leads formation from the ICs manufacturing to the printed board assembly.
The author made the following conclusions:
The second burn-off process of the ball leads at any stage of the process improves the strength of their attachment. Besides, the greatest increase of that strength is noted during the second burn-off process after the first burn-in stage.
Increase of the holding strength is also observed during the burn-off process before and after the burn-in, and the specified strength for various types of ICs differs significantly, its maximum increase is on the weakest ball leads.
After burn-off of all types of ICs displayed the similar data on the shear force that indicates the elimination of the causes reducing the strength of ball leads.
Physical form confirms the assumption on the existence of parasitic intermetallic layers.
After an additional burn-off of the ball-leads:
a) Control of their geometry did not reveal deviations from the initial state;
b) Functional control did not reveal changes of electric parameters of IC.
The obtained results demonstrate the necessity to include the interim and maybe finishing burn-off operation in the process of the metal-polymeric packages with ball-leads of the BGA type to increase the strength of their attachment.
Keywords:metal-polymeric BGA-casing, strength of leads’ mounting, microcircuits testing, burn-in testing, thermocycling, functional control
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