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IPC-9850 Official Proposal May 2001 6 1.4.5.1 Equipment Measurement equipment that meets or exceeds the required GR&R and accuracy specification limits under the specified evaluation procedures for a specified compon…

IPC-9850

Official Proposal

May 2001

minimizing the measurement-induced portion of the total error observed by the measurement machine, and are

particularly important because the specification limits for fine pitch components (QFP and BGA) are so tight.

For this standard, two QFP and one BGA slugs represent component types. Specifically, the QFP-100, QFP-208,

and BGA-228 component types permit the comparison of an extended range of chip-shooters with that of

specialized IC-placers and multi-functional placement systems. To maintain consistency when utilizing slugs, all

slugs in the pickup trays shall have the same orientation.

Other types of SMT components can be studied using the same basic methods defined in the standard. Glass slug

components that represent micro-BGA and Flip-Chips component types are obvious extensions of the standard that

suppliers or users may wish to consider. Rules for adding claims about additional component types are presented

later in this standard.

1.4.4 Test Panels The evaluation methods of this standard specify component placement into sticky media

dispensed on clear glass panels. This approach is advantageous for two reasons. The first is the dimensional stability

of the glass panel, as opposed to epoxy/glass PWB materials that are much more susceptible to shrinking and

wrapping. The second reason is that it permits use of a standard Optical Coordinate Measurement Machine (CMM)

to illuminate the outline of the components. CMMs are able to rapidly measure a large number of components with

very high precision.

In order to streamline the evaluation methodology, a single glass panel type is specified that permits placement

evaluation and verification of a variety of component types. This panel is referred to in this standard as the

Placement Verification Panel (PVP). The PVP has fiducial markings at specified locations with spacing accuracy

traceable to a NIST certification standard. These fiducials are used as references by both the placement and

measurement machines.

The panels accommodate the following component groups (one component group at a time) for this standard:

a. 36 QFP-100,

b. 30 QFP-208

c. 100 BGA-228

d. 80 SOIC16

e. 400 1608C (Capacitors)

Application of the sticky media requires experience. There must be sufficient amount of sticky media to hold the

component in place, but not too much as to cause interference with the back light intensity. Appendix C has

guidelines on the application of the sticky media.

1.4.5 Measurement This standard has been developed with emphasis on assuring that the measurement tools are

capable of properly characterizing the process. Capable measurement tools provide the customer with a

methodology for verifying vendor claims. They also assure the vendor that the customer is properly evaluating the

machine performance. For an Optical CMM to be a capable gauge for evaluating the surface mount process, its

accuracy and repeatability must be significantly higher that the accuracy and repeatability of the surface mount

equipment. The measurement capabilities required by the CMM depend on the type of components being evaluated

and on the specification limits that the supplier is committing to.

The accepted method for evaluating measurement system performance is called Gauge Repeatability and

Reproducibility (GR&R). This methodology determines the measurement system’s ability to consistently measure

the same product over and over again. The methodology requires that the measurement uncertainty (6x the GR&R

error) be at most 25% of the specification range of the product being measured. GR&R studies do not assess the

accuracy of the measurements, just their consistency. An additional check is needed to verify that the CMM

measurement routine is producing accurate results. See Appendix G for discussion.

The accuracy of the Optical CMM can only be evaluated against a certified gauge. The gauge selected for this

standard is a NIST traceable glass verification panel with etched images in the shapes of the selected components.

This panel is measured on the CMM, and the reported positions are compared to the actual positions of the

component images provided from the panel certification.

IPC-9850

Official Proposal

May 2001

1.4.5.1 Equipment Measurement equipment that meets or exceeds the required GR&R and accuracy specification

limits under the specified evaluation procedures for a specified component type is acceptable.

Automated Optical CMM machines are currently favored by many placement equipment vendors and users due to

their measurement speed. The rapid measurement speed is required due the large number of measurements required

to attain statistically meaningful characterization results. Although this method has been demonstrated to work well,

significant limitations are recognized. The limitations restrict interpretation of the results to the actual SMT process.

Since CMMs were originally developed for a machine shop environment, their lighting systems and measurement

tools are not optimized for measuring surface mount components. The machines are applied to the placement

evaluation process by utilizing clear PVPs that make available high quality images on the CMM. The components

are mounted onto the PVP, are illuminated, and then their positions are measured.

Limitations of the CMMs are their cost and lack of mobility. CMMs are expensive since they utilize many features

that provide structural rigidity, precise position, and high quality imaging. They require delicate calibration and are

sensitive to changes in the environmental conditions, which makes them non-portable.

1.4.5.2 Reporting Measurement results are recorded on standardized forms. The Placement Performance Metric is

form IPC-9850-F1. This form serves two distinct functions. The first is to report the general performance by

machine model type and the second is to validate the performance of a specific machine by serial number. Values

for speed and accuracy that are simultaneously achievable are listed. Form IPC-9850-F1 is supported by the CMM

Capability to Evaluate Metric Parameters form, IPC-9850-F3, which is used to demonstrate the measurement

validity of the parameters presented in the Placement Performance Metric.

The Reliability Performance form (IPC-9850-F2) provides an indication of typical results determined from values

reported by users. Unlike the Placement Performance Metric, which cites guaranteed performance, the Reliability

Performance form merely conveys typical reliability levels for the machine model type based upon a nominal

amount of data collected by the placement machine supplier’s customers in their factories. But this reliability

performance form does establish a foundation upon which the industry can raise the reliability, availability and

maintainability of the surface mount equipment infrastructure.

1.5 Forms Reproducible copies of all required forms are provided in Section 7.

1.6 Data Methods

With regards to the statistical treatment of placement deviation data, we have assumed that deviations generally

follow normal (Gaussian) distributions. This may not always be the case. There is nothing inherently wrong with

data having some other distribution. However, depending upon the circumstances, it might mean that the

specification limits at the two prescribed Cpk limits (1.33 and 2.0) contain some percentage of data less than the

99.9968% and 99.9999% percentages normally associated with these Cpk limits. It would be prudent for the user to

verify that the machine has data that reasonably approximates a normal distribution if it is crucial to the user that the

machine's level of inaccurate placements precisely matches those associated with Cpks of 1.33 or 2.0.

1.7 Terms and Definitions

Additional terms and definitions are provided in Table 4-4 and 4.1.1 through 4.1.11.

Fiducials are markings on substrate materials --such as PWBs or glass-- that are utilized by the placement

equipment vision systems to locate the position and orientation of the substrate.

Component refers to surface mount parts which are utilizes in the construction of electronic devices.

Placement Error is defined as the physical distance between where the component was actually placed and where

the surface mount equipment was specified to place the component by the placement program data.

Slug refers to a NIST certified glass panel with etched image of a single Component and reference fiducials.

dev

refers to the placement error in the X-direction (parallel to the “9850 Verification” label found on the

Placement Verification Panel).

IPC-9850

Official Proposal

May 2001

dev

refers to the placement error in the Y-direction direction (perpendicular to the “9850 Verification” label found

on the Placement Verification Panel).

θθ

dev

refers to the rotational placement error (about the component’s X-Y area centroid location).

Overhang refers to the portion of the lead’s width, at the lead’s tip, that extends off of the land’s edge. Overhang I

is due to placement error jointly caused by the X, Y, and θ deviations.

Assist is defined as an unplanned interruption that occurs during an equipment cycle where all three of the following

conditions apply:

• The interrupted equipment cycle is resumed through external intervention (e.g., by an operator or user, either

human or host computer).

• There is no replacement of a machine part (defined specifically to distinguish from component parts being

placed by the machine), other than vendor specified machine consumable parts.

• There is no further variation from specifications of equipment operations.

Build Time - The amount of time it takes the machine to pick and place all the components. This time period

includes fiducial read time and nozzle change time if any.

Failure is defined as any unplanned interruption or variance from the specifications of equipment operation other

than assists. Specifically, some part of the placement machine has to be replaced or the machine had to be turned off

and then back on in order to continue production.

Net Throughput - The number of Components Per Hour (CPH) the machine can place on the verification PVP.

Preventive Maintenance (PM) is a machine stop required by the supplier's published PM schedule.

Repeatability is defined as one standard deviation of the placement error when placing multiple components upon

multiple boards.

Tact Time - The average time required to place a single component while maintaining the specified placement

process capability. Excludes transfer time, fiducial time and nozzle change time.

Total Tact Time - The time required to place all components on verification glass verification panel while

maintaining the specified placement process capability. Excludes Transfer Time, Fiducial Time and Nozzle Change

Time.

Transfer time – The total transport time in and out of the machine, excluding the time the panel spends in the work-

area.

• Movement in and out of work area

• Time to clamp/release the board in the work area

Land The termination areas on the PWB referred to by the IPC-T-50 Terms and Definitions as a portion of a

conductive pattern usually, but not exclusively, used for the connection and/or attachment of components, also

commonly referred to as pads.

1.8 Units of Measurement All dimensions in this document are provided in hard metric (SI) followed by soft

English/Imperial in brackets. All components are referenced as a metric definition, i.e. 1608C is equivalent to the

0603 (60milx30mil) component type.

2. Referenced Documents

IPC-A-610 Acceptability of Electronic Assemblies

IPC-SM-782 Surface Mount Design and Land Pattern Standard

IPC-T-50 Terms and Definitions for Interconnecting and Packaging Electronic Circuits