Electronic Microscopic Research Of The Coating Involved In Electronic Components And Its Encapsulation Material

The reliance and demand of surface treatment and electroplating is becoming higher and higher with the electronic industry development. To improve the components reliability and encapsulation quality, the coating problems should be coated with the quality and failure of components manufacturing and packaging, and the relationship should be researched. The common nature of electroplating research combined with the case study in the later use can better promote the components and encapsulation quality improvement, even the industry development. Based on the microscopic analysis method, coating defects and subsequent failure involved in electronic components and packaging materials was analyzed, including gold-plated layer, lead frame copper-plated layer and electroless nickel layer, which provided reliable basis to solve the practical application. The main content of the research work and the achievement are as follows:(1) The secondary electron of scanning electron microscopy(SEM) can be used to reflect the composition of tested sample when the atomic number difference is large. In addition, the influence of surface carbon composition caused by accelerating voltage was studies. The result shows, as the voltage rises, C content gradually reduce, and the underlying substrate element signal begin to emerge and gradually rise. The above research provide basis for surface light element composition analysis when the surface and internal components is inconsistency.(2) Discoloration problem of lead frame plating copper layer were studied. First of all, discoloration types were classified on the basis of a large number of research data: discoloration caused by foreign substances attached was up to nearly 40%, including body fluids, oils and chip dust. Caused by copper plating layer morphology change was almost 50%. The rest 10% discoloration was caused by potassium carbonate crystal. Second, the experiment proved that secondary crystallization of copper layer leading to morphology change under the high temperature caused the discoloration. Affected by high temperature, light particles accumulation and pinhole appeared on the coating surface, and the surface smoothness was differed from the normal coating. All of the defect will have certain influence on complementary optical radiation, showing the discoloration on macro. Finally, the alkali and(CN)- in electroplating solution can absorb carbon dioxide to produce carbonate crystals coating on the surface of the crystal, which shows the deep red color point on the macro after the process of high temperature welding chip.(3) The gold-plated layer involved in electronic components and its encapsulation material was researched. the gold electric migration on the grid of MESFET causes the Au conductive layer resistance and temperature increase, and Au heat migration is heavy, which make metal particles between the gate and the source are stacked, which causes the gate wire off and unstable contact between the gate and the source, that causes MESFET parameters drift and lead to the amplifier output unstable; the spots area is uneven, poor gold layer smoothness is poor and surface area is increased. Water and Cl- is not only easy to attach to here, and can reach the kovar alloy layer through pore to react to form chloride and oxides, thus forming spots; Proving the method that gold mass percentage of the welding position is less than 3% after hot dip coating tin used to judge the eligibility of hot dip coating tin is available, when the thickness of gold-plated layer around the pin is less than 2.5μm; hot dip coating tin caused the exposure of copper layer. Under the galvanic situation, the reaction between copper(Cu) and sulfur(S) from bonding adhesive produced copper sulfide(CuS), which stacked on the wire, caused high resistance, concentrated heat, a local temperature rise, and further promoted the growth and accumulation of CuS, resulting in wire breakage, or even rupture, causing the inductor even amplifier failure.(4) The plating solution pollution and plating spots problems of electroless nickel layer were researched. Electroless plating solution remained in the blind angle and thread mouth, generating the cracks traces, which performed coating fall off on the macro. The color of high phosphorus coating deposition was dark overall, with a high internal stress, and cracks was easily exist. What’s more, H2 remained in plating makes the plating with high internal stress easily blistered. At this time, Sodium salt and sulfate in plating solution penetrated into the blister area, producing corrosion solution and coating spots on macro.