Must pay attention to the Solder Ball Issues of BGA Componen
2018-11-23 17:48Writer: qyadminReading:
As electronic products grow towards portability, miniaturization, networking and multiple medium, higher demands have been laid to packaging technology of multi-chip devices with new high-density package technologies constantly coming into being among which BGA (ball grid array) is the most prevalent. Through changing peripheral leads mode applied by traditional packages, BGA contains solder balls which are actually Pb/Sn solder bumped joints playing a role as leads under its base. Compared with traditional packaging mode, BGA features advantages of numerous I/O per unit area, low lead inductance and capacitance, excellent thermal dissipation and low demand of alignment, all of which leads BGA package to the mainstream of modern package technologies.
In spite of so many advantages introduced in previous paragraph, BGA package features defects as well, especially in terms of quality control during filter. This article will provide some measures on quality control of BGA components based on their properties.
Possible Abnormities of BGA Components during Filter
Possible abnormities of BGA components during filter primarily come in two types: solder balls and cover plate. The former includes solder ball damage, solder ball falling and solder ball oxidation while the latter can never be determined unless GJB548B-2005 is used as a reference.
• Solder Ball Damage and Cover Plate Scratch
Solder ball damage and cover plate scratch take place mostly as a result of mismatching with aging socket which further leads to high temperature and aging of components.
Test sockets for BGA packaging come in two types: needlepoint type and claw type. Needlepoint-type test socket features a needlepoint shape of contact method between solder balls and socket, that is, point-to-ball type. This type of socket tends to cause needle points on solder balls and needlepoint tends to become deformed after long-term application, which then cause solder ball damage. Claw-type sockets are those sockets with complete solder balls embraced in test tank. This type of sockets tend to cause abrasion which then leads bumping to take place at peripheral of solder balls due to abrasion of test tank. In one word, both needlepoint-type sockets and claw-type sockets will cause solder ball damage after long-term application.
• Solder Ball Falling
Solder ball falling belongs to an accidental phenomenon and failure often takes place at nickel-plated surface or gold-plated surface. Solder ball falling is possibly associated with pad surface such as pollution and nickel oxidation. In the process of reflow soldering, adhesion is not good between solder paste and pad, leading solder balls to fall during humidity test. Another possible reason for solder ball falling is associated with gold-plated thickness on the surface of pad because too thick gold and tin tends to generate brittle metal alloy, leading solder balls to fall.
• Solder Ball Oxidation
Solder ball oxidation seldom occurs during first filter for quality inspection on BGA-package components. The longer solder balls are exposed to the air, the more easily oxidation will take place. As a result, solder ball oxidation usually takes place in second filter process. Therefore, it's of much significance to stop solder balls from oxidation when it comes to BGA components quality control.