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Use of Wrong Thickness Technique Gives Bad Test Results

Use of Wrong Thickness Technique Gives Bad Test Results

The information that follows pertains to:

Software Revisions: 6.x; Hardware: 5DX, TDW; ID #: 2000-12-032-01

Beginning with release 6.0, there are two techniques for measurement of solder thickness on the Agilent 5DX, each based on use of a different Confirmation & Adjustment panel. Differences in the two techniques are discussed below. It is imperative that individual panel programs specify the use of adjustments that are current on the system.

If systems are adjusted using the Agilent 5DX_1024 and Agilent 5DX_512 programs, it is necessary to specify the thickness tables based on the new technique in order to have a meaningful test. To do this a token needs to be added to the panel.ndf file of each application:

.MATERIALS: 6337_CU

or

.MATERIALS: DEFAULT

These are equivalent. If there is no .MATERIALS line, the system will use the older technique, and thickness tables that were never adjusted for that system. The result will be thickness measurements that are unrealistic and will likely vary over time for the same board. This will result in an increase of false alarms, and incompatibility of thresholds with programs set up using the properly adjusted thickness technique. There will be sizeable effort required to convert these applications to the new technique.

If systems are adjusted using both techniques (Agilent 5DX_1024 and Agilent 5DX_512 and 4PICALIB/XXX_SUB and 4PICALIB/XXX_2X2 programs, where XXX is the serial number of the system), the use of the either technique is acceptable. We strongly recommend use of the new technique for new panel programs. See below.

If systems are adjusted using only the 4PICALIBXXX/SUB and 4PICALIBXXX/2X2 programs, the old technique should be used (no .MATERIALS line in the panel.ndf file). If the .MATERIALS line is added, there will be an error message when attempting to load the CAD for this application, since these systems will typically not have the required files.

Solder Thickness Techniques

The older technique used for measuring solder thickness on the 5DX is based on the 4PICALIBXXX/SUB and 4PICALIBXXX/2X2 programs. The C&A panel for these programs has series of lead dots of varying thickness shaded by varying amounts of copper. Thickness tables are constructed during the adjustment process based on the gray levels of these dots compared with the background gray levels (the gray levels of the shading) at different camera indices.

The newer technique adjusts solder thickness based on eutectic tin-lead solder (63:37) strips and copper shading. From this, thickness tables for solder shaded by copper and solder shaded by solder are constructed, also as a function of camera index.

NOTE: to specify the use of the solder shaded by solder thickness tables, the materials identification line should read:

.MATERIALS: 6337

It would also be possible to adjust the system for different solder alloys (including lead-free) and different shading materials, using this technique and strips of the appropriate materials.

Use of the newer method results in more accurate and more consistent thickness measurements under various shading conditions. The end result will be fewer false alarms and faster board setup because of a decreased need to subtype or otherwise deal with shaded joints in a different manner.