Strips of ICs mounted on substrates are widely used in CSPs and other high-density package processing.

The trend is to mold the strip as a unit—rather than as an individual part—covering all the parts in one or a few cavities, making visual site tracking impossible through the assembly process. For strip testing, strip maps are required between test, singulation and parts placement in a shipping medium.

As strip maps become more widely employed, non-usersnon-users are beginning to take notice of their benefits.

At SEMI’s TAP conference in Singapore this year, a paper presented by speakers from Infinity Systems and Cypress Semiconductor detailed an assembly and test system using strip maps.

The system is hands-off from die attach through test to tape-and-reel, and spans a cycle time of eight hours. Strip maps allow tracking defects by site, stacking strip maps to look for site problems and automated program selection. The use of the maps also eliminates 80 pieces of paper formerly needed for tracking.

By definition, strip maps are the storage of strip-site information in a computer database (See figure). The figure diagrams the following:

• Strip ID
• Strip orientation/origin
• Rows in the strip
• Columns in the strip
• Cell status, Mark mark grade, Package package grade, or Sort sort grade

The last item, cell status, contains the information on the cells. This data changes depending on the process. The cell information is supplied as an array of numbers defined by the product of the row and column count.

Currently, strip maps are being employed in manufacturing and are being standardized by SEMI. (See standards at semi.org.) The following SEMI documents cover maps:

• Map Data Items G81
• Map Data File Format Doc #3157
• Map Data Protocol Doc #3154

Used in packaging, the map data will be transferred between equipment through the factory computer. The map transfer is initiated when a strip enters the equipment and the strip ID is read. The equipment then uploads the ID and the factory computer downloads the strip map.

The equipment processes the material on the strip and updates the strip map with new cell information. When the strip completes processing, the equipment uploads the updated map.

Diagram illustrates typical assembly strip map items.

The strip identity is mandatory for using the strip map, because the strip ID defines the identity of the map. The strip ID is a 2D code placed on the strip plane near the strip's strip’s leading edge. This allows the equipment to read the strip ID when it enters the equipment. Details of the strip mark are given in the SEMI standard for strip marking,T-9.

Strip IDs and maps are enabling new levels of control and automation in assembly processing. The tracking and control is by strip rather than by assembly lot. This means that strips can be the basic unit in CSP processing, and the importance of the lot is diminished. For example, a lot can be broken down into strips for parallel processing to reduce cycle time.

Strip maps require new functions on assembly equipment. Additionally, the factory computer must support managing the association between sort grade, cell status, mark and test grade.

When this support has been enabled, the equipment and factory computer communications can be integrated, allowing strip maps to provide a more efficient and shorter CSP assembly process.