Endoscopy inspection in electronics-detect BGA defects

Endoscopy is known to be used in medicine, but it can also be used in other areas of industry like electronics.

In big electronic industries where investments are huge, the requirements for quality are also big. In big industries, there is automatic testing using. This allows achieving maximum quality with minimal cost. In smaller industries, there is a requirement to inspect almost every product to avoid faults. One of the biggest problems that may occur is soldering errors, position errors, or other defects. For visual defect identification, endoscopy is often used.

Endoscopy in electronics is some AOI (Automatic Optical Inspection), often used to check BGA pins. The endoscope usually consists of a light source directed by fibber glass and an optical sensor with variable focus. Changing focal length, it is possible to view about 50mm area while space between chip and board can be only 0.05mm. Information from the optical sensor can be sent to a computer for further processing. Comparing to the X-RAY method, optical inspection of electronic devices is cheaper.

The biggest problem in visual inspection is defect detection. Visual inspection is more subjective than objective. The testing results usually depend on the quality engineers. If there is no obvious disjoint of lead, then decisions can vary depending on specialists’ conclusions.

To detect defects, organizations usually use a database of common defects to compare results and make the right decision. Inspection is experience-based. Previous results help to improve future testing results. There is a whole theory about this, so that I won’t go into this right now.

Endoscopy inspections help detect bad solder joints under BGA packages as there is no other way to do this except the X-RAY method. This is the best choice for smaller organizations that haven’t any automatic fault detection systems. Endoscopy is not for massive series of electronic products at it is a time-consuming process.

Let’s take on the example of the optical inspection system. It would be LS 3000 constructed by the PACE organization. It is used for controlling the quality of soldering such packages as PBGA, CSP, Flip Chips, LBGA, CBGA. This system can also be used for labs where new technologies are being adapted.

The system consists of a high-resolution CCD video camera and sensors. Image from the CCD camera is transferred to the computer screen. Main features:

• the magnitude from 100 up to 375 times;
• field from 1.5 to 6.35;
• focus from zero to 228mm;
• minimal space between component and board – 0.05mm;
• minimal space between components;
• contains optical sensors with LEDs and optical fiber;

More information can be found in manufacturers site: paceworldwide.com