semi合集-English.pdf - 第6246页
SEMI G48-89 © SEMI 1989, 1996 3 Centerline of Packa g e = (T2 + T1)/2; (B2 + B1)/2. (Relative to datum) NOTE: Figure 2 calculations assume that th e leadframe centerline is equ idistant between T3 and the zero datum poin…
SEMI G48-89 © SEMI 1989, 1996 2
4.1.8 Bottom Cavity Width (Section 5.8)
4.1.9 Cavity Overlap/Underlap (Section 5.9)
4.1.10 Cavity to Cavity Mismatch (Section 5.10)
4.1.11 Cavity Depth (Section 5.11)
4.1.12 Molding Protrusions (Section 5.12)
4.1.13 Pin Depths (Section 5.13)
4.1.14 Dambar Trimming Defects (Section 5.14)
4.1.15 Package Warpage (Section 5.15)
4.1.16 Lead Coplanarity (Section 5.16)
4.1.17 Shoulder Bend Location (Section 5.17)
4.1.18 Surface Finish (Section 5.18)
4.1.19 Radii (Section 5.19)
4.1.20 Lead Position (Section 5.20)
4.1.21 Draft Angles (Section 5.21)
4.1.22 Lead Spread (Section 5.22)
4.1.23 Foot Angle (Section 5.23)
4.1.24 Foot Length (Section 5.24)
4.1.25 Plastic Stand-off (Section 5.25)
4.2 Conditions
4.2.1 All measurements to be made on molded
components, which have been processed to agreed
conditions including post mold cure.
4.2.2 All measurements to be performed at a
temperature between 20° and 26.7° C (68° , 80° F).
4.2.3 Axis Definition
4.2.3.1 The X axis lies parallel to the rail of the frame
and the Y axis lies perpendicular to the rails of the
frame.
4.2.3.2 The package X and Y axes must be positioned
parallel to the X and Y axes of the measurement stage
travel to avoid measurement errors.
4.2.3.3 The datum of the X and Y axes is the pilot hole
of the leadframe, because it is the most accurate feature.
An additional pilot hole is required to establish the theta
datum.
4.2.3.4 The Z axis is perpendicular to the X and Y axis.
The datum is the leadframe or the top mold parting line,
unless otherwise specified.
5 Measurement
5.1 Package Thickness — (Figure 1)
5.1.1 Equipment — Micrometer
5.1.2 Using the micrometer, measure the thickness of
the package at three (3) places, diagonally across the
package, where the contours allow, at the top edge,
middle and bottom edge of the package. (Note: the top
is the pin 1 identifier edge.)
5.2 Package Length — (Figure 1)
5.2.1 Equipment — Optical Comparator at 10×.
5.2.2 Position the package so that the cross-sectional
view is presented for measurement. Use care to assure
the package is square to the datum plane.
5.2.3 Align the package side draft angle (see Section
5.21) where the draft angle intersects the leadframe.
This is the parting line (datum point). Measure the
overall width at the parting line, including cavity
mismatch.
5.3 Package Width — (Figure 1)
5.3.1 Equipment — Optical Comparator at 10×.
5.3.2 Position the package so that the cross-sectional
view is presented for measurement. Use care to assure
the package is square to the datum plane.
5.3.3 Align the package side draft angle (see Section
5.21) where the draft angle intersects the leadframe.
This is the parting line (datum point). Measure the
overall width at the parting line including cavity
mismatch.
5.4 Leadframe to Cavity Offset — (Figure 2)
5.4.1 Equipment — Toolmaker’s Microscope at 30×.
5.4.2 Position the circle (cross hair) of the filar
eyepiece of similar diameter to the leadframe pilot hole.
Zero the digital readout. Move the stage to the point
where the molded package meets the leadframe at the
parting line. Record digital readout reading as (T1).
Continue to move the stage until the point on the
opposite side where mold compound and leadframe
meet. Record digital readout reading as T2. Continue to
move stage to center of leadframe rail (usually also a
hole). Record the digital readout reading as T3.
5.4.3 Turn part over and BE SURE TO USE THE
SAME HOLE AND PART; repeat the three (3)
readings, B1, B2, and B3.
5.4.4 Derive the data from the readings as follows:
Top Centerline of Frame = (T3)/2
Bottom Centerline of Frame = (B3)/2
Measurement Error = (T3)/2 - (B3)/2
Frame Cavity Offset = (B3)/2 - (B2 + B1)/2
SEMI G48-89 © SEMI 1989, 1996 3
Centerline of Package = (T2 + T1)/2; (B2 + B1)/2.
(Relative to datum)
NOTE: Figure 2 calculations assume that the leadframe
centerline is equidistant between T3 and the zero datum point.
5.4.5 In lieu of the frame pilot hole, the dambar may be
used on the frame when measuring the offset; however,
the possibility of tolerance error may become
cumulative, particularly with etched rather than
stamped frames.
NOTE: By SEMI convention the offsets are defined in
relation to the bottom cavity of the mold.
5.5 Top Cavity Length “Y” Axis — (Figure 2)
5.5.1 Equipment — Toolmaker’s Microscope at 30×.
5.5.2 Focus the microscope on the leadframe datum
point. Zero the digital readout. Move the stage to the
intersection of the mold compound and the leadframe
parting line. Read and record. Continue to measure
across the package length to the intersection of the
mold compound and the leadframe parting line on the
opposite edge of the package. Read and record.
5.5.3 The cavity length is defined as (Ty2 – Ty1).
5.6 Top Cavity Width “X” Axis — (Figure 2)
5.6.1 Equipment — Toolmaker’s Microscope at 30×.
5.6.2 Focus the microscope on the leadframe datum
point. Zero the digital readout. Move the stage to the
intersection of the mold compound and the leadframe
parting line. Read and record the reading. Continue on
to the intersection of the mold compound and the
leadframe parting line on the opposite side. Read and
record.
5.6.3 The cavity width is defined as Tx2 – Tx1.
5.7 Bottom Cavity Length “X” Axis — (Figure 2)
5.7.1 Equipment — Toolmaker’s Microscope at 30×.
5.7.2 Focus the microscope on the same datum point
used for the top cavity length (remember the package
has been turned over). Zero the digital readout. Move to
the intersection of the mold compound and the
leadframe parting line. Read and record the reading.
Continue to the intersection of the mold compound and
the leadframe parting line on the opposite side. Read
and record. The bottom cavity length is the difference
of the two readings. Record the bottom cavity length
(By2 – By1).
5.8 Bottom Cavity Width “X” Axis — (Figure 2)
5.8.1 Equipment — Toolmaker’s Microscope at 30×.
5.8.2 Focus the microscope on the leadframe datum
point. Zero the digital readout. Move the stage to the
intersection of the mold compound and the leadframe
parting line. Read and record. The bottom cavity width
is the difference of the two readings (Bx2 – Bx1).
5.9 Cavity Overlap/Underlap — (Figure 4)
5.9.1 Compare the top cavity length to the bottom
cavity length and the top cavity width to the bottom
cavity width. The difference in the number is the
overlap/underlap for each axis.
5.10 Cavity to Cavity Mismatch — (Figure 2)
5.10.1 The comparison of the centerlines of the top
cavity length to the bottom cavity length and the top
cavity width to the bottom cavity width shall determine
the cavity to cavity mismatch.
Formula:
Cavity to Cavity Mismatch =
(B2 + B1)/2 – (T2 + T1)/2
5.11 Cavity Depth — (Figure 1)
5.11.1 Equipment — Depth Indicator
5.11.2 Top Cavity Depth — Measure the distance from
the top surface of the leadframe to the top of the unit,
place the indicator on the surface of the leadframe,
zeroing the readout, moving the part to a point where
the top of the unit can be indicated, and read and record
the readout.
5.11.3 Bottom Cavity Depth — The measurement is
performed in the same manner as the measurement in
Section 5.11.2 except the part is turned over and the
bottom surface of the leadframe to the bottom of the
unit is used.
5.11.4 The package depth is the sum of the frame
thickness and the top and bottom depth. (This
measurement should equal Section 5.1. Any variation
may be considered measurement error.)
5.12 Molding Protrusions Top/Bottom of Part —
(Figure 3)
5.12.1 Equipment — Digital depth indicator.
5.12.2 Place unit on the anvil and zero the indicator on
the package surface away from area of protrusion.
Carefully move the part to where the protrusion is
located. Carefully lower the indicator to the top of the
mold protrusion. Read and record the mold protrusion.
5.13 Pin Depths — (Figure 3)
5.13.1 Equipment — Depth indicator with a fine point
or “Z” axis reading toolmaker’s microscope.
5.13.2 The measurement is made from the nominal
plane of the package surface to the bottom of the design
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).