DOD-HDBK-344 f USAF)
5.2 Procedure A - Part fraction defective - R&M 2000 goals and •incoming defect density
5.2.1
Objective.
Provide
assurance
that
the manufacturing
process
begins with
electronic
parts
(diodes, transistors, etc.) with R&M 2000 part fraction defective goals of below 1000 PPM by FY87 and
below 100 PPM by FY90,
Obtain planning estimates of incoming defect density which will serve as a basis
for planning a stress screening program,
5.2.2
Procedure Al.
R&M 2000 goals on electronic part fraction defective. The methodology uses either
an industry accepted lot acceptance procedure for verifying compliance with the Specified Quality Level
(SQL) in PPM (EIA Interim Standard No. 18) or a lot acceptance procedure based on a constant Average
Outgoing Quality Limit (AOQL).
a.
There are several ways that the SQL or AOQL can be applied.
The parts vendors can use process control and testing with sufficient documentation of their
product's quality to the original equipment manufacturer (OEM) or Air Force agency buying their parts to
assure both the OEM and the government that the parts do in fact meet the defective rate requirements.
b.
The OEM can perform
receiving
inspection
and screening to assess the defective rate of the
purchased parts.
c.
The OEM can use the results of first assembly screening to assess the defect rate of the purchased
parts. (See Procedures El, Step 5).
The lot sampling approach contained
constant Lot Tolerance Percent Defective
protection.
in the EIA Interim Standard
(No.
18) employs essentially a
(LTPD) for a given SQL and therefore
provides
good
buyer
Alternatively, a constant AOQL approach permits smaller sample sizes for the higher quality
vendors and still assures the accepted product meets the quality requirements. The sample sizes for lower
quality products would be slightly larger than those in the EIA Standard.
prepared as an alternative to the EIA Standard.
and
1,000 PPM
Therefore, Table 5 has been
While Table 5 contains sampling plans only for 100 PPM
levels, the sample sizes are linearly related to defective rates so plans for other
defective levels are easily obtained.
For example, for 500 PPM the sample sizes for 1,000 PPM are doubled
and the number of defectives permitted is unchanged.
The
values
in Table
5 are based
on
using
the Binomial
distribution
to
approximate
the
exact
probability of acceptance. This approximation is not accurate for cases where the number of samples is a
large fraction of the total lot.
Therefore, it is necessary that the sampling plan selected maintain the
lot size to sample size ratio above five to one. For example, for the 1,000 PPM requirement and a lot size
of 5,000 items, only the sampling for zero or one defective may be used.
S o u r c e : h t t p : / / w w w . a s s i s t d o c s . c o m -- D o w n l o a d e d : 2 0 1 3 - 0 2 - 2 8 T 1 2 : 4 0 Z
C h e c k t h e s o u r c e to v e r i f y t h a t t h i s is the c u r r e n t v e r s i o n b e f o r e u s e .