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Topside Ball Grid Array (BGA) Registration Disclosure Number: IPCOM000004806D
Original Publication Date: 2001-Jun-11
Included in the Prior Art Database: 2001-Jun-11
Document File: 2 page(s) / 3M

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Tzann-Sheng Lin: AUTHOR [+1]


Topside Ball Grid Array (BGA) Registration

This text was extracted from a WORD97 document.
This is the abbreviated version, containing approximately 100% of the total text.

Use of a BGA (ball grid array) to contain electronic circuits is becoming more popular, because such parts are small in form factor but have many I/O pins, or balls. The balls, which may have separations as small as 0.5 mm, provide contact to the printed circuit board and are all located on the bottom of the package. Because these connections are only on the bottom of the package, and are so close together and small, it is practically impossible to use any visual inspection techniques to make sure the part is properly placed. Thus, the only check that can be performed is a functional board test, which is very time consuming and does not identify marginally placed BGA's. Marginally placed BGA's form poor solder joints that are likely to fail over time in the field. BGA's are also a nightmare to repair once soldered, because there are many balls in a very small area.

The present invention proposes placing one or more precision markings on the topside of a BGA in the manufacturing process of the BGA. The precision markings identify precisely where the pins are in relation to balls. Fig 1 shows the BGA packaging with laser markings. At the BGA assembly level:

1. Create a pair of Fiducial marks for each BGA package on the strip.

2. Use the fiducial marks for die attach and laser marking

3. Laser mark a pair of fiducial marks on top of the BGA

4. Use the laser marks on top of the BGA during placement to confirm the BGA placement accuracy.

These markings would be utilized for inspection by automated inspection processes (that already exist in factories today) by accurately finding the center of the ball grid. Parts that are improperly placed will be caught prior to soldering, thus saving costly repairs and eliminating likely failures from reaching the field. Utilizing BGAs so marked and the inspection process will further allow us to incorporate statistical process control over the placement process for BGAs, thus proactively maintaining good placement quality, which is not possible today.

Substantial cost saving savings can be realized by implementing this invention, not including field failures or customer service issues. This invention would be applicable industry wide to all BGA users.

Fig 1: BGA Package with laser marking