Printed circuit board packing of BGA
1. There are three advantages for IC adopting BGA packaging:
It has the advantages of solid appearance, small volume, high density, short path, and less noise and electricity.The common P-BGA can withstand 6-8W power.
2. Among all BGA packaging components, more than 16-64 feet account for more than half
208 feet over 5 percent.The common foot distance or ball distance is between 0.65mm and 1.27mm.At present, the ball distance of closely spaced mass production has been close to 0.5mm and 0.4mm, while the most densely packed in the current trial production is 0.3mm. It will be very hard to put on the PCB surface.
3. The normal ball diameter accounts for about 60% of the ball distance
The ball diameter of the tight distance shall also be fixed at 0.3mm.The ball foot of 1-3 ring around the bottom of the abdomen is mostly set as signal ball, one of which is easy to escape from the square array due to the wiring, and the other is less functional failure due to its better welding reliability (but it is not suitable to set the ball at four corners).The refractory inner ball can only be used as power source, ground and heat dissipation.
4. The current packaging form has become the template of various system modules
The large complex interconnect vehicle, which can carry multiple chips (including laminates) and passive components, is specially called MDS.In order to facilitate the cleaning and insulation of the bottom of the abdomen, the rack height after assembly shall be kept above 0.4-0.5mm.
5. All kinds of BGA pellets in N2
To maintain stability of volume and solidity (within 3-6%), high adhesion solder is used as a temporary and permanent solder and no more highly varying solder solder.In fact, the planking plate of the ball planting stage is prone to curve, and the common surface of each ball foot is required to be 0.15mm on average.Therefore, the subsequent BGA assembly should not be placed on the Central Line of the PCB, in case that the board is bent again and the coplanarity is lost.The ball material used is Sn63, and will be changed to lead-free solder (mainly SAC305) from July 2006.
6. The top surface of the loading plate shall be lined with an crystal
The working surface must be plated with nickel and electroplated.As a result, the bottom of the plate ball pad also had to be plated nickel.To prevent the golden brittleness in welding, the thickness of gold should be 1.0 thickness m, and the width of the edge of the cushion climbed by the green paint limit is about 0.1mm.
7. It is very difficult to assemble and weld
For example, eye test, wet-sensitive water huai MSL, heavy industry, cost, supply chain, and Voiding < empty).Once the p-bga encapsulation device absorbs water, it will often become warped at high temperature.Otherwise easy to swell, exposure meters flower, and cracking, on the dorsal fin is more prone to bend, often makes corner up and welding is bad, and above 260 ℃ will be even more dangerous.
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