Solder Ball issues of BGA components and their Remedies
BGA (Ball grid array) is a technique which is used for integrated circuits. It is a surface mount packaging. BGA is used to permanently mount microprocessors. BGA is array of pins as its name suggests. It provides connection between integrated circuit and printed circuit board. In BGA there are pads instead of pins.It also provides more interconnection pins.
BGA has three main advantages:
- 1. BGA has higher density.
- 2. BGA is a solution for production of miniature packages for an integrated circuit with multiple pins.
- 3. BGA provide good heat dissipation characteristics and protect from thermal deformation. It also has low inductance with leads.
In last few decades the electronic components industry have been grown towards more portability, networking and multiple pins medium, and all theses advancements laid to increase in packaging technique of multiple chip products. And BGA is one of them, which is relevant in this domain. BGA as its name suggests contains solder balls which is combination of Pb/Sn. Compared to other packaging mode BGA offers large I/O area, lower values of inductance and capacitance excellent heat dissipation. All these features make the BGA technology most favorable in modern packaging technology.
Despite having all these advantages BGA also has certain defects. Possible defects which are coming are for solder ball and cover plates. The solder ball includes; solder ball damage, falling and oxidation and the second one can be calculated by some standard references. All these defects are explained below.
1. Solder Ball Damage:
This defect occurs because mismatching and aging socket and this leads to increase in temperature. Testsocket in BGA are of type viz. needlepoint and claw type. The former has a needlepoint contact shape between solder balls and the socket (i.e. point to ball type). This needlepoint cause problem in long term, because the needlepoint get deformed since it is in contact with solder ball. The claw-type is sockets with completely embrace the solder balls. This kind of socket cause abrasion and ultimately bumping. In conclusion both needlepoint and claw socket cause damage to the solder ball for long runs.
2. Solder Ball Falling:
It is more prone to failure, and those failures takes place at nickel-coated surface either gold coated-surface. Nickel oxidation also cause problem of failure. By the time of soldering the adhesion is good between soldering material and the pad. If the gold pad thickness is too high it will create an alloy with soldering material which is highly brittle.
3. Solder Ball Oxidation:
Solder ball oxidation usually occurs during the quality inspection. If the solder exposed to the air for a longer time, more easily the surface will get oxidized. In the subsequent processes we can see the continuous oxidation of the solder ball surface. Therefore there is a requirement of quality control in terms of reducing the oxidation of solder balls.
Remedies: The above mentioned issues can be avoided by following the mentioned solutions
1. These defects require frequent inspection, by various suitable methods. And it is also required to keep the solder ball in well protected environment during transportation, storage and in other places as well.
2. Process control is also required. During manufacturing solder balls could suffer from damage issues. In order to avoid this we are required to follow the standard procedure of manufacturing regarding the pcb material, process and parameters.
3. During the test phase it is required to keep safe the solder ball from oxidation. So to provide that anti oxidizing environment the solder balls usually keep in nitrogen atmosphere.
4. Reversal of BGA required to be done through pallet made of non-static foam, which is essentially been given for protection of BGA components.
5. During testing only one or two samples are required to be checked whether scratches takes place in plate and damage issue with the solder balls. This part is also related with the physical protection as well. When abnormalities are explicit, test should not be continued for the test of the sockets unless the defected samples got repaired.
6. With time the feature of a particular socket will get reduced dramatically, for the defined life time. Therefore it is essential to evaluate the life time of the BGA so that user could make proper arrangement for maintenance of the system, in due time. How many are required to be tested in one time, this also be given before the testing procedure. Inspection is required to be carried out after and before the test, so that any single point of mistake must not be remains within the unit.
7. As it is always mentioned in the conventional manufacturing that quality must be maintained from the starting. This quality control is required to be exercised by all the members involved in the production team including all managers, line workers and all the other staff. In order to standardize the operation involved in the manufacturing, the line workers are required to be trained and to minimize the quality loss during the various processes. After this quality inspection and its feedback also have equal importance. The statics related to quality control must be reported. Data of quality control, problems in batches, and major quality hazards all these details must be given to the customers in order to maintain the reliability of the product.
The quality system is required to be monitored continuously by auditing or other means. Whenever there is a quality an issue arises, improvement measure must be taken from the management side.