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SEMI G48-89 © SEMI 1989, 1996 5 5.17.2 The measurement is made from the intersection of the straight part of the sh oulder with the shoulder bend radius of the lead on one side of the pac kage to the same point on the le…

SEMI G48-89 © SEMI 1989, 1996 4

mark (either ejector pin or Pin #1 indicator or other

feature).

5.13.3 The indicator is set to zero on the package

surface and then moved to the bottom of the feature.

The readout is read and recorded.

5.14 Dambar Trimming Defects — (Figure 4)

5.14.1 Equipment — Toolmaker’s Microscope

5.14.2 Measure from the edge of the lead to the edge of

the protrusion or intrusion; record the reading and the

lead number.

NOTE: Dambar trimming defects are those which can be

caused by overcutting into the lead shoulder (stand off) i.e.

cutting too much or undercutting the dambar, leaving too

much dambar or a burr. Overcutting causes shoulder

intrusions. Undercutting leaves shoulder protrusions. In some

cases, an adjacent protrusion and intrusion is caused by

misalignment of the part at the time of dambar removal.

5.15 Package Warpage — (Figure 5)

5.15.1 Equipment — Microscope “Z” Axis reading

40×.

5.15.2 With the package sitting on the stage, obtain a

two point datum by measuring two-points on opposite

edges 0.005 from the radius readings; move to the

center of the package and obtain the deviation from the

datum, and read and record the reading as the warp.

5.15.3 For quad packages, it is equally important that

there be minimum warp in each axis (X or Y) so that a

three-point Z axis datum must be obtained; the two

used in 5.15.2 and an additional one, on one adjacent

edge.

5.16 Lead Coplanarity

NOTE: Applies to all surface mount devices.

5.16.1 Contact Method — (Figure 6)

NOTE: Not recommended for gull-wing leads.

5.16.1.1 Equipment

Dial Indicator 0.0001" Accuracy, 5 grams maximum

pressure.

Granite Flat.

Transfer Stand.

Package Holding Fixture.

Reference Gauge Blocks, 0.0002" Accuracy.

5.16.1.2 Place the package on holding fixture so that

the flat sections of the leads, as they exit from the

plastic, are on the ground flats of the fixture. The leads

are to be facing “UP” (Dead Bug).

5.16.1.3 On the granite flat, set up the dial indicator on

its transfer stand and zero the reading using the

reference block. Use a suitable reference block so that

all measurements are positive to avoid confusion.

5.16.1.4 Measure the highest point on each lead (e.g.,

the tangent point of a “J” lead).

5.16.1.5 Determine the range of readings.

NOTE: Special Precautions

1. Be sure that the flat of the leadframe, as it exits

from the plastic, rests on the flats of the holding

fixture. If the radiused section supports the package,

then spurious readings will result.

2. The pressure exerted by the dial indicator must not

exceed 5 grams. To check the contact pressure of

the dial indicator, use a gram gauge. The gram

pressure must be noted at the initial deflection of the

gauge and at the maximum deflection of the gauge.

If the initial deflection is greater than 5 grams, then

the point where 5 grams is obtained must be noted

and the measurement must stay within this range to

be valid.

5.16.2 Comparator/Mirror Method

5.16.2.1 Equipment — Optical comparator with at least

20× magnification as per Section 3.1.2. Mirror, flat

within 0.0005 inch with a mirror finish having the

reflective suface on top. (A polished silver wafer is

suggested.)

5.16.2.2 Place the mirror on the measurement stage

mirrored side up with the mirror in the plane of the XY

axis. Place the package on the mirror with the leads

down. Sufficient mirror must extend past the leads

toward the lens of the comparator so that an image of

the leads with its reflection can be viewed. Focus on the

leads nearest the lens. (Care must be taken not to focus

on the leads on the opposite side of the package.) (See

Figure 8.)

5.16.2.3 Measure the distance between the lead tip and

its reflection. Divide that measurement by two to obtain

the coplanarity of the lead.

5.16.2.4 Repeat for each lead. Rotate part to measure

all sides. Determine co-planarity by identifying

maximum measurement.

5.17 Shoulder Bend Location — (Figures 1, 7, and 7a)

NOTE: This measurement is not precise, since radius tangent

locations allow for considerable inspector interpretation.

5.17.1 Equipment — Comparator at 20× magnifica-

tion. (Surface and shadow illumination).

SEMI G48-89 © SEMI 1989, 1996 5

5.17.2 The measurement is made from the intersection

of the straight part of the shoulder with the shoulder

bend radius of the lead on one side of the package to the

same point on the lead on the opposite side of the

package. Locate this point on the first lead by lining up

the vertical comparator cross hair with the straight of

the lead. Bring the center point of the cross hair to this

intersection. Zero the readout, move to the opposite

lead, and repeat the location of the intersection. Record

the measurement.

NOTE: Due to shadowing of leads, only the end leads on the

package can be measured. A visual check with a 10 to 20×

microscope should be made to check for gross difference of

other leads.

5.18 Surface Finish

5.18.1 Comparative Method — (EDM Finishes only)

5.18.1.1 Equipment — Charmille Standard Surface

Gauge Binocular Microscope and Light.

5.18.1.2 Insert gauge and molded package to be

checked into a holder so that both can be viewed at the

same time under the microscope.

5.18.1.3 Estimate the surface finish on the package.

5.18.2 Absolute Method

5.18.2.1 Equipment — Automatic Surface Analyzer

Surface Standards.

5.18.2.2 Calibrate the analyzer using the gauges.

5.18.2.3 Measure the surface finish on the package.

The analyzer gives the average roughness (R

) and the

actual surface roughness. Use average roughness for

acceptance.

5.18.3 Table of approximate equivalent finishes

Mirror

Satin

Extra

Fine

Medium

Course

Micro

Inches

4 30 ± 10 50 ± 10 75 ± 10 105 ± 10 145 ± 10

Charmilles N/A N/A 18–21 21–24 24–27 27–30

Microns N/A 1 1.5 2 2.5 3.5

5.19 Radii

5.19.1 Comparative Method

5.19.1.1 Equipment — Optical comparator at 20×.

5.19.1.2 Radii are measured by comparison to known

radius overlays marked at the same magnification as the

comparator.

5.19.2 Absolute Method

5.19.2.1 Equipment — Toolmaker’s Microscope.

5.19.2.2 Radii are measured using the reticle lines and

the X and Y axes to obtain the radius.

5.19.2.3 Care must be taken to assure that each radius

is measured separately.

5.20 Lead Position

NOTE: Lead position is a combination of pitch variations due

to lead movement after forming and lead width. If the lead is

to fit a solder pad or hole, the combination must be

considered. In some cases, the lead width can be a major

contributor to poor lead position, eg. SO packages with gull-

wing leads, PCC with J bend.

5.20.1 Comparative Method

NOTE: This method will only determine if the part is usable,

not the breakdown of width and pitch variations.

5.20.1.1 Equipment — Optical Comparator at 20×.

5.20.1.2 Align the package to an overlay displaying

limit lines for lead pitch/width.

5.20.2 Absolute Method

5.20.2.1 Equipment — Toolmaker’s Microscope.

5.20.2.2 Move to the edge of the lead number and zero

the readout.

NOTE: Where there is a definitive end to the lead as in the

case of SO, SIP and DP, the end of the lead at the intersection

of the lead in feature, will be the measurement point. Quad

PCC packages will be measured at the top of the “J” bend

when in the “Dead Bug” position.

5.20.2.3 Move to the opposite edge of that lead and

record width.

5.20.2.4 Move to the first edge of the next lead. Record

the measurement. Repeat the width measurements.

5.20.2.5 Repeat for all leads to be measured.

5.20.2.6 Pitch can be calculated from the

measurements.

5.21 Draft Angles

5.21.1 Package Sides

5.21.1.1 Equipment — Optical comparator at 10x.

5.21.1.2 Lay the top or bottom surface of the package

squarely onto the comparator to insure that no

protrusions on the surface cause the package to be

tilted. Align the horizontal cross-hair to the leadframe.

Using the vertical cross hair, compare the draft angles

to an overlay.

NOTE: This measurement should be taken before the leads

are formed.

5.21.1.3 Repeat the procedure for all sides of the

package.

5.21.2 Pin Marks (e.g., Pin 1 indicator at end of

package).

5.21.2.1 Equipment — Toolmaker’s Microscope.

5.21.2.2 Focus the microscope on the surface of the

package and measure the diameter of the pin hole. (D1)

5.21.2.3 Focus on the bottom surface of the pin hole

and measure the diameter. (D2)

5.21.2.4 Tangent of Draft angle = (D1 – D2)/2H where

H is pin depth from Section 5.12 or cavity thickness.

5.21.2.5 In some cases ejector pin holes may require

measurement if a deep hole is specified.

5.22 Lead Spread — (Figures 1, 7, and 7a)

5.22.1 MDIP, SO — (Figure 7, 7a)

5.22.1.1 Equipment — Optical Comparator at 10×

Magnification.

5.22.1.2 Place the package squarely on the comparator

with the leads “UP” and find the mid-point of the

bottom cavity width.

5.22.1.3 Measure the distance to the outer edge of each

row of leads at the widest point of spread.

5.22.2 PCC (J bend lead dimension) (Foot Print)

Measure from perpendicular to the greatest extension of

the “J” radius of the leads on one side of the package to

the perpendicular tangent to the greatest extension of

the “J” radius of the leads on the opposite package side.

(See Figure 1.)

5.23 Foot Angle — (Figure 7)

NOTE: Applies to gull-wing leads.

5.23.1 Equipment — Optical Comparator at 20×

Magnification. Device Holding Fixture (see Section

5.16).

5.23.2 Place the device in the fixture, so that the flat

section of the leadframe at the junction with the plastic

body rests on the fixture’s flats. Leads to be facing

“UP”.

NOTE: Do not rest the radiused sections of the leads on the

flats. Be sure that all mold flash is removed from the area of

the frame that rests on the flats.

5.23.3 Measure the angle of the foot with respect to the

horizontal.

5.24 Foot Length — (Figure 7)

NOTE: Applies to gull-wing leads.

5.24.1 Equipment — Optical Comparator at 20×

Magnification. Device Holding Fixture (see Section

5.23).

5.24.2 While the foot angle is being measured, place a

circle template that contains the same radius as the

formed part onto the comparator. Align this template to

the radius of the outside bend. Where the radius of the

template meets the radius of the outside bend, this is the

tangent point to measure foot length.

5.25 Stand-Off

5.25.1 Measure the plastic stand-off, when applicable,

using the procedures of Section 5.12.

5.26 Lead Sweep

5.26.1 Equipment — Toolmaker’s Microscope or

Optical Comparator.

5.26.2 Method

5.26.2.1 Determine centerline of lead at egress of lead

from molded body (CL1) (see Figure 4).

5.26.2.2 Determine centerline at the end of the lead

(CL2). The difference between the two centerlines

CL2 – CL1, shall be the lead sweep.

NOTE: On “J” lead devices, the end of the lead is defined as

the bottom of the “J” lead radius.

5.26.3 Cautionary Notes

5.26.3.1 Verify centerlines on leadframe before

measuring to ensure lead-frame is correct.

5.26.3.2 Verify lead position in relation to the top

cavity centerline.