IPC9850_Surface Mount Equipment Characterization.pdf - 第26页

IPC-9850 Official Proposal May 2001 26 provided by the NIST certification for the unique glass panel utilized. The closer the CMM measurement values are to the certified locations the better the measurement capability of…

IPC-9850

Official Proposal

May 2001

Suppliers may include procedures to measure placements with the placement machine itself. This is acceptable for a

particular placement machine as long as that particular machine (not just a sample machine from that particular

model type) passes the gauge requirements laid out in this section which determine whether or not its measurement

capability is acceptable.

5.1 Gauge Repeatability and Reproducibility Capability

This verification procedure determines the CMM's ability to repeat and reproduce the component location and

rotation mounted onto the PVP. This evaluation shall be made for each component type.

While multiple GR&R methodologies are available, this standard uses the traditional average-range method and

recommends the use of the spreadsheet discussed in Appendix H. The results are reported in terms of the upper and

lower specification limits that yield a precision-to-tolerance ratio of better than 25%.

Although a precision-to-tolerance (P/T) ratio of less than 20% is usually considered acceptable, 25% is utilized in

this standard to accommodate existing CMM machines. However this reduced P/T ratio specification if somewhat

offset by the fact that the analysis is performed using a more stringent requirement of six sigma (+/-3 sigma or

99.7%) versus the customary value of 5.15 sigma (+/- 2.575 sigma or 99%) recommended by the Automotive

Industry Action Group (AIAG).

Measurement Procedure Obtain a single glass verification panel with a specific part type populated according to the

procedures described in the machine placement performance metric, Section 3. Measure the populated PVP three

consecutive times. The PVP is to be completely removed and replaced from the CMM for each run. Only 36

components need to be measured for each run. Appendix F outlines the component locations for the specific

component panel layout. After the three measurements are obtained the CMM must be shutdown and restarted.

The same PVP plate shall be subjected to two additional measurement cycles (two more sets of 3 measurements)

using an identical procedure. At least two operators should be utilized to obtain the three sets of data. The entire

GR&R evaluation shall be performed in a time period no longer than it takes to perform the measurement of the

consecutive four PVPs for the placement performance evaluation.

For the SOIC-16 and 1608C components, the center of the component shall be measured using the lead outline and

component outline, respectively. The same measurement procedure applies to the PVP populated with slugs.

However, since the CMM utilizes the fiducial markings on all glass slugs, regardless of the specific component

image, it is only necessary to evaluate the CMM’s ability to measure the slugs using the fiducial markings and not

individually for the QFP and BGA component types. Appendix D provides suggested methods for measurement

methods.

5.2 Accuracy Capability

This verification procedure determines the Optical CMM's ability to accurately measure the placement of

components on the glass verification panel. This is accomplished by evaluating the CMM’s ability to measure the

NIST certified glass verification panel specified in Figure 5-1. This accuracy verification panel (AVP) was designed

to evaluate the CMM’s ability to measure three component types required for compliance with Section 3.

To evaluate the measurement capabilities of the 1608C and SOIC-16 components, their images have been etched

onto the AVP. Since slugs are utilized for the QFP and BGA components, only slug fiducials marking are etched

onto the AVP. Some of the etched images are translated and rotated from their specified CAD location, in order to

test the CMM’s ability to measure components with measurement error. Some of the 1608C and SOIC-16

component images on the AVP are translated in a range of + 50 micrometers, and rotated in a range of +3º range.

Some of the four fiducial image sets will be translated in a range of + 25 micrometers, and rotated in a range of +1º

range. The ‘CMM Accuracy Eval.xls’ file provides an instruction guide and a sample CMM accuracy evaluation

spreadsheet.

This methodology is implemented using a measurement program on the CMM, which searches for the components

on the glass panel at their CAD locations. These CAD locations are the centers of the components as if no

translation or rotations were applied to the images on the glass panel. The CAD locations of the images can be found

in Appendix F. The CMM measurement results are compared to the locations and rotations of the component images

IPC-9850

Official Proposal

May 2001

provided by the NIST certification for the unique glass panel utilized. The closer the CMM measurement values are

to the certified locations the better the measurement capability of the CMM.

The results are reported in terms of the upper and lower specification limits that yield process capability indexes

equal to 2.0. See Appendix B for discussion.

Measurement Procedure Measure the center location and orientation of the component images on the certified

accuracy verification panel a single time. Measure the center location and orientation of each group of four fiducials

that represent the slug component types. Use the same image analysis procedures that are utilized for the Placement

Performance Metric evaluation. Appendix D provides a guide for the proper methods of measuring the center

locations of the components.

Calculation Method Subtract the CMM measured image locations from the NIST certified image locations along the

X, Y and θ axes, for each of the 1608C, SOIC-16, and slug features. This provides a distribution of the measurement

errors of the CMM. Use these distributions to calculate the average and standard deviation for each axis. Calculate

the process specification limits for each axis using the following equations, when Cpk = 2.0. See Appendix B for a

discussion of these equations.

SL=3*SD

Error

*Cpk+|Avg

Error

where Avg

Error

∑

−=

)(

ocationCertifiedLcationMeasuredLo

and SD

Error

)(

118

ocationCertifiedLcationMeasuredLo −

−

∑

Figure 5-1 Accuracy Verification Panel

IPC-9850

Official Proposal

May 2001

6 Test Vehicles

Users of this standard shall utilize standardized materials and methods to ensure that users and suppliers of SMT

placement equipment are able to observe the same placement performance results within the tolerance of their

measurement gauge’s repeatability, reproducibility and accuracy.

Table 6-1 is the material list for the execution of the placement performance evaluation. Check the IPC website for

suggested suppliers of evaluation material.

Table 6-1 Tool Kit Materials List For Performance Evaluation

Quantity Material

4 Placement Verification Panel (see Figure 6-2)

1 CMM Measurement Verification Panel

150 QFP-100 slugs with no background or with white background

130 QFP-208 slugs with no background or with white background

150 BGA-228 slugs with no background or with white background

1600+ 1608C Components

240+ SOIC 16 Components

Optional

4 PVPl Carrier

- Sticky tape

6.1 Placement Verification Panel Specifications

Glass verification panels with anti-reflective chrome metallization are used because they are dimensionally stable

and can be made very accurately. The glass board fiducials create stable high-contrast images on both placement

machines and CMMs. The transparent glass allows the use of back lighting on the CMM to increase the gauge

repeatability of the measurements.

The IPC-9850-P1 placement verification panel (Figure 6-1) was designed to be small enough to measure on

relatively affordable vision CMMs and large enough to represent a typical sized PWB.