IPC9850_Surface Mount Equipment Characterization.pdf - 第17页
IPC-9850 Official Proposal May 2001 17 If the component is placed so that the long sides are along the board’s Y-axis, Maximum Lead Tip Error (MLTE) = ) ev sin( 2 ) , max( d S S ydev y x θ ⋅ + Ball-to-Land (BTL) refers t…
IPC-9850
Official Proposal
May 2001
16
Land sizes are defined by IPC-SM-782. Termination sizes used here are the nominal values (average of the
minimum and maximum values) (see Table 3-1). The Cpk is calculated relative to the 50% and 75% coverage called
for in the assembly standards.
Table 3-1 NEEDS TITLE
Component
Type
Component
Length x
Width
Termination
Width
Land
Length x
Width
Spec Limits for
Total Error
(Class 1,2)
Spec Limits for
Total Error
(Class 3)
SOIC-16 8.89 x 6.0 0.42 NA x 0.60 0.300
1
0.195
1
QFP-100 16.0 x 16.0 0.20 NA x 0.30 0.150
2
0.100
2
QFP-208 32.0 x 32.0 0.20 NA x 0.30 0.150
2
0.100
2
BGA-228 15.0 x 15.0 0.50 (Dia.) 0.45 (Dia.) 0.207
3
0.114
3
Notes
1. Requiring Total Error (for leaded this is MLTE) to be ≤ 0.195 for this SOIC is equivalent to requiring Lead-to-
Land to be ≥ 75%. The Total Error limit of 0.3 corresponds to LTL ≥ 50%.
2. Requiring Total Error (for leaded this is MLTE) to be ≤ 0.100 for this QFP is equivalent to requiring Lead-to-
Land to be ≥ 75%. The Total Error limit of 0.15 corresponds to LTL ≥ 50%.
3. Requiring Total Error (for area array this is MBE) to be ≤ 0.114 is equivalent to requiring Lead-to-Land to be ≥
75%. The Total Error limit of 0.207 corresponds to LTL ≥ 50%.
Calculation Method Calculation methods are provided for three component types: two leaded, one area array.
Termination-to-land calculations are based on IPC-SM-782 designed termination and designed land dimensions,
rather than actual ones. At time of publication of this standard, there is no standard for ball to land ratios for area
array components. A 0.5 mm diameter ball with a 0.45 mm land for the BGA228 was selected for calculation of this
metric.
Lead-to-land (LTL): is based on the percentage of the lead’s width that is placed on land. This measurement
quantifies the error for a component’s lead that experiences the most offset (of all the leads) due to the joint x, y, and
θ errors.
Calculation for a component with leads on four sides is shown here:
LTL=
⋅−
−
−
%100100
2
LeadWidth
LeadWidthLandWidth
MLTE
, where MLTE is defined below:
For a rectangular or square component with leads on four sides:
Maximum Lead Tip Error (MLTE) =
⋅+
⋅+
)sin(
2
)sin(
2
max
dev
S
xdev
dev
S
ydev
y
x
θ
θ
For a rectangular or square component with leads on its two longest sides:
If the component is placed so that the long sides are along the board’s X-axis,
Maximum Lead Tip Error (MLTE) = )evsin(
2
),max(
d
SS
xdev
yx
θ
⋅+
IPC-9850
Official Proposal
May 2001
17
If the component is placed so that the long sides are along the board’s Y-axis,
Maximum Lead Tip Error (MLTE) = )evsin(
2
),max(
d
SS
ydev
yx
θ
⋅+
Ball-to-Land (BTL) refers to the percentage of the BGA ball or column of an area array components that is placed
on its (round) land. BTL quantifies the error for the “ball” that experiences the most offset (of all the balls) due to
the joint x, y, and θ errors.
BTL= 100
R
A
1
2
1
•
−
π
, where
( ) ( ) ( )
+−−−
∆−
+∆−−
∆−
−
−−−−
2
1
2
2
22
2
1
2
2
1
1
2
1
2
2
1
1
2
1
R
c
sin
2
R
cR
2
c
1sin
2
R
2
R
rc
sin
2
R
rcR
2
rc
1Sin
2
R
2 =A
where:
∆X = |Xdev| + |
2
x
S
- (
2
x
S
· cos (θdev) -
2
y
S
· sin (θdev)) |
∆Y = |Ydev| + |
2
y
S
- (
2
y
S
· cos (θdev) +
2
x
S
· sin (θdev)) |
22
YX= ∆+∆∆r
c =
r
2
RrR
2
B
22
L
∆
−∆+
R
L
= radius of the land
R
B
= radius of the ball
R
1
= min(Radius of Ball, Radius of Pad)
R
2
= max(Radius of Ball, Radius of Pad)
Xdev = Offset of component along the X-axis from the target placement
Ydev = Offset of component along the Y-axis from the target placement
θdev = Rotational offset of component from the target placement
∆X = Maximum offset along the X-axis of the ball from its target placement
∆Y = Maximum offset along the Y-axis of the ball from the target placement
∆r = Radial offset of ball center to pad center. Synonymous with MBE in this document.
Computational note: the values of
Sin
1−
(x) need to be expressed in radians (rather than degrees).
Example of Computing Cpk limits for Termination-to-Land Coverage: After the x,y, and theta errors have been
determined by the CMM (for a four board run using one particular component type), and the individual components’
Termination-to-Land computations have been made as well (using the equations above), the next step is to calculate
the mean and standard deviation of this group of Termination-to-Land values. The Cpk equation should then be
applied, using first the 50% specification limit and then the 75% limit. These 2 Cpk values then go in the
Performance Reporting Form. Suppose the mean of the 144 Termination-to-Land values in a QFP100 run is 85%
and the standard deviation of these values is 5%. Then Cpk versus 50% requirement is 33.2
5
3
5085
=
•
−
.
IPC-9850
Official Proposal
May 2001
18
4 Attribute Defect Rate and Reliability Performance Metric-- Form IPC-9850-F2
Complete evaluation of an SMT placement system must not only consider placement capability performance
covered by Form IPC-9850-F1, but also include information about the yield and reliability of the system. Like the
general performance use of Form IPC-9850-F1, Form IPC-9850-F2 shall be used to present the expected attribute
defect rate and reliability of a specific machine model. However, unlike Form IPC-9850-F1 there shall be no
requirement for a validation for a specific individual machine and there shall be no guarantee for the warranty
period associated with IPC-9850-F2.
The selected reliability metric parameters for this standard fall into three categories -- reliability, availability, and
maintainability. With the exception of Attribute Defect Rate, parameters are based on the SEMI E10-0699E
standard.
The information presented in this form shall be gathered and reported according to this standard, and shall reflect
the performance of the same machine model as in the Placement Performance Metric. The following information is
reported on this form:
1. Manufacturer Name, Machine Model
2. Attribute Defect Rate (ppm)
3. Mean Placements Between Assists (MPBA)
4. Mean Time To Recover from assists (MTTR
a
)
5. Mean Placements Between Failures (MPBF)
6. Mean Time To Repair failures (MTTR
f
)
7. Equipment Dependent Uptime
8. Amount of Preventative Maintenance per 6000 Hours
9. Mispick Rate (ppm)
10. Data Collected From:
a. Number of Factories
b. Number of Machines
c. Total Number of Placements
4.1 Attribute Defect Rate
Although production yield depends on the solder paste printing quality of the PWBs, sticky media is used for this
procedure instead solder paste. It is recognized that the attribute defect level from placement operations on sticky
tape are likely to be lower than defect levels from placement on solder paste or conductive adhesives in production
runs. However use of solder paste introduces many additional variables such as paste viscosity, tackiness and height.
The use of sticky tape provides a method to compare machines with a minimum number of variables. In addition, it
eliminates the need for vendors to have costly screen-printing equipment and expertise in utilizing stencil printing,
board cleaning processes, and controlled disposal of residual solder paste.
Since products assembled by surface mount equipment vary greatly by the type of component mix and size of the
PWB, a special kit is provided. This kit is designed to be representative of the product of a ‘typical user’. This
‘typical user’ kit is made of 4400 components and shall be mounted onto the PWB with sticky media. Table 4-1
provides a list of the 4400 component types and quantities. Because some equipment is not designed to place all
SMT parts, it may not capable of placing this specific set of components. If it is necessary to change the mix of
components, the test shall be run using a similar mix of component types that are within the machine’s capability.
The selected mix of components shall be clearly stated on form IPC-9850-F2. The components shall be presented to
the machine using standard feeders or trays manufactured by a vendor-approved supplier.