Many friends in circuit board factories often ask: how to design BGA to strengthen and improve its strength to prevent BGA cracking (crack)? Because some customers complain about BGA cracking on circuit boards, the company must have someone responsible for it.
In fact, shouldn’t these high-level people be most responsible? Not only require product design to be light and thin, but also require to catch up with the schedule, shortening the original 12-month new product cycle to nine months, and now it is compressed to six months , and the ID is constantly changing, the schedule cannot be delayed, and the product design must be perfect, these engineers can only work hard, sell their livers, and everyone is in danger. How did this company culture become? like this?
Before we start discussing this issue, we must first understand why BGA cracks. Leaving aside the manufacturing problem, assuming that all BGA solder balls are well soldered and IMC is formed well, but BGA cracks still occur. The main reason should be Stress, the reason for this conclusion is that for all products that have been analyzed, the problem of falling or cracking parts on the circuit board is almost absolutely related to stress.
There are several sources of stress for circuit board parts falling or tin cracking:
1. Stress comes from external impact or pressure
Taking mobile phones as an example, the most likely external stress is bending in the pocket ((iPhonebplus bending door incident), or the impact caused by accidentally dropping it on the ground. 2. Stress comes from internal creep
For example, when a circuit board or BGA package is deformed by reflow at high temperature, the stress will not stop until it reaches an equilibrium point. This equilibrium point may also be when the solder ball cracks.
3. Stress comes from thermal expansion and contraction caused by ambient temperature changes
In some areas, it freezes outdoors in winter, and when the product moves from an indoor heated environment to an outdoor environment, drastic temperature changes will occur; in tropical areas, there is air conditioning indoors, and a huge temperature change will occur when moving from indoors to outdoors. Not to mention accidentally or intentionally putting the product in the car, the temperature rises in the sun during the day, and the temperature drops rapidly at night. The reason why temperature is important is that different materials have different expansion coefficients. The expansion coefficient of circuit boards is definitely different from that of solderballs, and it is also different from the material of BGA packaging. Imagine that ordinary roads and bridges will be designed with "expandable "Seam" to reduce the risk of thermal expansion and contraction of materials, but it seems that electronic materials can only try to find materials with a relatively small expansion coefficient.
