Mechanical Properties of QFP Joints Soldered with SnAgCu and SnPb Solders

With the development of lead-free solder alloys, the investiagtion focusing on the relibility of lead-free solders are essential. Since the reliability database of lead-free solder joints needs to be further supplied, the creep behavior of SnAgCu soldered joints on Quad Flat Package （QFP） devices under thermo cycling load are studied in this paper, compared to conventional SnPb solder, by finite element simulation based on Garofalo-Arrhenius creep model. Meanwhile, the mechanical properties of SnAgCu and SnPb soldered joints in the pitches of QFP devices are also carried out by means of tensile test. The results indicate that the values of strain and stress of SnAgCu soldered joints were all smaller than those of SnPb under thermal cycling, and the tensile strength of the joints soldered with SnAgCu solder was higher than that of SnPb, which means the reliability of the joints soldered with SnAgCu solder is better than SnPb soldered joints. As the fracture surface morphology of the soldered joints compared, SnAgCu soldered joint presented ductile fracture, while the fracture mechanism of SnPb solder joints displayed both brittle and ductile fracture. Above all, the experimental results is in accord with that of simulation, which will provide guidance for reliability study and application of lead-free solders.

Ka-band broadband filtering packaging antenna based on through-glass vias (TGVs)

This work presents a novel design of Ka-band(33 GHz)filtering packaging antenna(FPA)that features broadband and great filtering response,and is based on glass packaging material and through-glass via(TGV)technologies.Compared to traditional packaging materials(printed circuit board,low temperature co-fired ceramic,Si,etc.),TGVs are more suitable for miniaturization(millimeter-wave three-dimensional(3D)packaging devices)and have superior microwave performance.Glass substrate can realize 3D high-density interconnection through bonding technology,while the coefficient of thermal expansion(CTE)matches that of silicon.Furthermore,the stacking of glass substrate enables high-density interconnections and is compatible with micro-electro-mechanical system technology.The proposed antenna radiation patch is composed of a patch antenna and a bandpass filter(BPF)whose reflection coefficients are almost complementary.The BPF unit has three pairs ofλg/4 slots(defect microstrip structure,DMS)and twoλg/2 U-shaped slots(defect ground structure,DGS).The proposed antenna achieves large bandwidth and high radiation efficiency,which may be related to the stacking of glass substrate and TGV feed.In addition,the introduction of four radiation nulls can effectively improve the suppression level in the stopband.To demonstrate the performance of the proposed design,a 33-GHz broadband filtering antenna is optimized,debugged,and measured.The antenna could achieve|S11|<-10 dB in 29.4‒36.4 GHz,and yield an impedance matching bandwidth up to 21.2%,with the stopband suppression level at higher than 16.5 dB.The measurement results of the proposed antenna are a realized gain of~6.5 dBi and radiation efficiency of~89%.