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Method of detecting BGA welding quality

Method of detecting BGA welding quality


In terms of the BGA due to the solder balls on the chip below, completion of welding is hard to judge the

welding quality. In the absence of inspection equipment of the first visual observation of BGA, and the

outer circle weld spot condition (as shown in Figure 2) then the chip against the light, if each row of each

column can be through the light so we can conclude that no welding, sometimes large size of solder ball

can also be seen. However, this method can not be used to determine whether the solder joints in the

presence of other defects or whether there are voids inside the solder joints. To determine the quality

of the solder joint, a X solder joint inspection instrument is used.


Traditional two-dimensional X-ray direct photographic equipment is cheaper, but the disadvantage is in

two sides of the PCB board all the solder joints are also in a photo developing. For components on two

sides of the same position, the formation of these solder shadows will overlap points not clear which is

the surface of the component, if defective, it is not clear which layer. This can not meet the requirements

for accurately determining the welding defect.


Another 5DX HP board inspection gauge is specifically designed to inspect the solder joints of the X ray

tomography inspection equipment. Of course, it can not only check the BGA, the board all the solder joints

it can check. Although it was previously thought that this device was too expensive for solder joints

inspection cost too high but with the application of BGA devices more and more people can accept this

expensive equipment.. 5DX X is a HP ray tomography, which can generate the effect of the film by layering

the welding ball.. X-ray tomography images are able to according to the original CAD design data and user

set parameters of automatic analysis of solder joints, it in real time for tomography in tens of seconds or 2

minutes (depending on the circuit board solder joints, the number and complexity of both sides of the PCB

all components of all solder joints are exact contrast analysis of welding qualified or not the conclusion.

Why is there a very high effect of the X ray photography of tomography? This is determined by its working

principle. The HP ray of the 5DX X system is produced by a X ray tube located at the upper end of the

device. At work, the voltage must be raised from 160KV to 200V, and the current is 100mA. The electron

beam produced under high voltage can produce X ray on the tungsten metal.This a bunch of X-ray diagonal

shot down to 7.6 (Rev / sec speed high-speed rotation, also in the following is not a scintillator platform with

the same speed and X-ray synchronous rotation. The flash device is actually a receiver for X light sensitive.

Generally speaking, metal tin, lead and other heavy metal X light will not through, will form a dark scene and

the general material is X ray penetrate what can not see. X - ray in a position between the light source and the

scintillator platform aggregation appear a aggregation plane, plane objects or images gathered will form a

clear image on the scintillator platform, but not on the plane of the object or image gathered in the scintillator

platform is is fire except that only a shadow. The principle of X ray tomography is shown in Figure 3. So for

PCB with different height of solder joint fault and want to check a layer of welding conditions as long as the

adjustment to gather the plane position will be very clear scan results show.



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