MIL- STD-883F 2004 TEST METHOD STANDARD MICROCIRCUITS - 第376页

MIL-STD-883F METHOD 2023.5 19 August 1994 4 3.2.1. 2 Applic able manufac turing pr oces ses. Applic able manufac turi ng proces ses incl uding bond pad metal di spos ition, glass ivati on etch, and worst case pac kage s …

MIL-STD-883F

METHOD 2023.5

19 August 1994

Also, RF/microwave hybrids that contain tuning wires (designated wires that will alter RF performance when moved) or

wires that cannot be accessed with a pull hook must be simulated on a test coupon in such a way to allow hook access for

purposes of pull testing. These wires are to be bonded at the same time the production hybrids are bonded using the same

setup, operator, schedule, and elements (electrical rejects may be used). The test coupon wires are to be pull tested in lieu

of the tuning or inaccessible wires on the production hybrid. Failures on the test coupon shall be considered as failures to

production units and appropriate action is to be taken in accordance with the applicable specification (figure 2023-2).

TABLE I. Nondestructive pull forces

AL and AU wire

diameter

(inches)

Pull force

(gf)

Pull force

(gf)

0.0007

0.0010

0.00125

0.0013

0.0015

0.0030

1.2

2.0

2.5

3.0

9.5

1.6

2.4

3.2

4.0

12.0

NOTES:

1. Nondestructive pull force values for wire sizes not specified

shall be 80 percent of the preseal pull forces for aluminum or

gold wire given in method 2011.

2. Tolerances shall be ±0.3 gf for pull forces up to 6 gf and ±5

percent for pull forces above 6 gf.

3. Any bond subjected to a nondestructive pull force exceeding

the specified pull force and the positive tolerance shall be

eliminated and not counted toward the PDA failures.

3.2 Alternative procedure

. This alternate procedure may be used where 100 percent non-destructive bond pull cannot be

performed because of high pin count (greater than or equal to 84 terminals) and small bonding wire pitch at the package

post (less than or equal to 12 mils).

3.2.1 In-process controls

. In order for a manufacturer to use the alternate procedure, a SPC program shall be

implemented for the wire bond operation in accordance with EIA-557-A, Statistical Process Control Systems. Any change in

the various effects shown to be significant by the characterization with respect to wire bond strength shall require a re-

characterization of the wire bonding process for the changed effect(s) on wire bond integrity. For QML, the SPC program

and the requirements listed herein shall be approved by the qualifying activity and may be subject to an audit at any time by

the government qualification activity. For Non-Jan devices, the SPC program and the requirements listed herein are subject

to review by the government agency responsible for the acquisition or their designee. All statistical evaluation,

characterizations, and designed experiments shall be available for review.

3.2.1.1 Applicable incoming materials

. Applicable incoming materials including wafer pad metallization targets, package

bonding post, and bonding wire shall have their critical characteristics determined and made requirements for acceptance

using either incoming inspection or vendor SPC data. Critical characteristics shall include possible sources of material

contamination (e.g. excessive carbon content in aluminum wire). Also, the applicable incoming inspection requirements of

MIL-PRF-38535 or MIL-PRF-38534 shall apply.

MIL-STD-883F

METHOD 2023.5

19 August 1994

3.2.1.2 Applicable manufacturing processes. Applicable manufacturing processes including bond pad metal disposition,

glassivation etch, and worst case package seal excursion shall have their critical characteristics determined and placed

under SPC control. Also, the process control requirements of the applicable general specification shall apply for these

operations including contamination controls, preventative maintenance procedures and schedules, and complete removal of

glassivation from the bonding pad.

3.2.1.3 For packages with gold plated posts

. For packages with gold plated posts, the device manufacturer shall perform

a bake test on one device from each incoming package lot. This test shall evaluate for basic plating or contamination

anomalies of the package post. The package shall be wire bonded post-to-post. The wire bonded package shall be baked

at 300 degrees celsius for 1 hour in either air or inert atmosphere. Bond strength shall then be tested in accordance with

MIL-STD-883, method 2011, using a sample size number = 45, C = 0 on the number of wires pulled. If any bond strength

failure is determined to be package plating or contamination related then the package lot shall not be used for this

alternative unless the defect can be effectively screened and the package lot resampled to a tightened sample size number

= 76, C = 0 for the number of wires pulled.

3.2.1.4 An active foreign material control program

. An active foreign material control program shall be in accordance with

MIL-STD-883, method 2010 or method 2017. A procedure and system for storing and handling wafers, packages, related

piece parts, and unsealed devices that will prevent contamination through package seal including face masks, lint free

gloves, restrictions on particle generating make-up, hair covers, and cleanroom gowns.

3.2.1.5 A 100 percent pre-bond visual inspection procedure

. A 100 percent pre-bond visual inspection procedure of the

die pads and package post shall be documented. The visual inspection shall be performed at 100-200X in a class 100

environment. Cleaning to remove rejectable contamination is allowed. No device shall exhibit evidence of the following

criteria:

a. Glassivation on the designed open contact area of the bond pads.

b. Chemical, film, photoresist or liquid contamination on the pads or posts.

c. Particulate and /or foreign material contamination on the pads or the critical bond area of the posts greater than

0.25 mils in diameter.

d. Die pads and package posts that do not meet all applicable requirements of MIL-STD-883, method 2010, condition

A or method 2017.

NOTE: 100 percent pre-bond visual inspection may be waived by the qualifying activity provided a 100 percent pre-

clean of pads and posts is performed, and all pads and posts for five (5) randomly selected devices pass the

inspection criteria. Precleaning may also be waived by the qualifying activity if historical data demonstrates the

cleaning is unnecessary. No cleaning is allowed during sample inspection. A 100 percent pre-clean and sample

inspection of 5(0) may be repeated a maximum of two times. Rejection of the sample after the second pre-clean

shall result in a 100 percent pre-bond inspection of the lot in accordance with 3.2.1.5. An investigation of the

rejects in the lot and sample shall be required and corrective action, as necessary shall be instituted. Until then,

100 percent pre-bond inspection is required. Once the effectiveness of any corrective action has been

determined, the 100 percent pre-bond inspection may be eliminated.

3.2.1.6 Bonding machine parameters

. Bonding machine parameters (e.g., temperatures, pressure, timing, fixtures, wire

size, wire material, height settings, etc.) must be defined for each die/package combination. The bonding equipment

parameters ranges shall be optimized by designed experiments. The experiments shall consider variations in bonding wire

geometry (e.g., loop height, wire length, shelf height, etc.). The experiments shall establish the predicted strength and

tolerance of the bonding operation. The allowable performance ranges of the bonding parameters determined by controlled

experiments shall be documented. Equipment parameter changes outside the allowable limits must be evaluated and

documented as to still meeting the predicted wire pull strength and tolerance.

Note: ASTM Standards F 458 and F 459 may be used as guideline documents.

MIL-STD-883F

METHOD 2023.5

19 August 1994

3.2.1.7 Process capability study. After the wirebond process has been demonstrated to be in a condition of stability and

statistical control, a process capability study shall demonstrate that the probability of any device failing the minimum

post-seal bond strength is P <.0001. The probability must meet the accumulative probability at the device level and not at

the individual wire level. The distributional form of the post-seal bond strengths shall be statistically evaluated for

conformance to the selected sampling distribution (e.g., Gaussian, lognormal, Wiebull, etc.). The capability study sample

size shall be sufficient to detect a shift in the distribution of the worst case package/die combination to a 100 parts per

million level. The beta risk to the consumer shall be .001 or less. (See Appendix A for normal distribution example.) The

process capability study shall be performed periodically. The capability study may be accomplished by characterizing the

wire pull strengths of one or more worst case package/die combinations. Selection of the worst case package/die

combinations should consider wire geometry, number of wires, pads and post sizes, etc. The characterization results from

worst case package/die combinations must be readily extended to all devices.

3.2.1.8 Control limits and action procedures

. The results of the evaluations in 3.2.1.6 and 3.2.1.7 shall be used in

determining control limits and action procedures for the wire bond operation. A destructive wire bond strength sampling plan

for each wire bonder shall include start and completion of each assembly lot, frequency of sampling the assembly lot, and

changes in operators (manual wire bonding only), wire spools, package lots, or setup conditions. The bond strength data

shall include the force required for failure, the physical location of failure, and the nature of the failure. Electrical rejects from

the same wafer lot may be used for the destructive wire bond pulls. In the event that bond wire strengths are outside the

predicted values for the wire, or class of wires with similar geometry, the bonder shall be inactivated immediately and not

returned to production until tests show that the operation is back under statistical control. A procedure for the traceability,

recovery, and disposition of all units bonded since the last successful bond strength test is required.

3.2.1.9 Time and temperature characterization

. Initially, a time and temperature characterization shall be performed for

each major type of wire bond metallurgical interface (e.g., gold/aluminum, etc.) to determine the electrical and mechanical

integrity of the wire bonds with respect to such factors as; flexing of wire bonds due to thermal expansion, and microcracks

or microvoids at the metallurgical interface. Evidence from the characterization shall demonstrate that the integrity of the

bonds is sufficient for a device to function over its expected life. Life usage conditions shall exceed 50,000 cycles from a 0 -

85 degree Celsius temperature range at the bonds. Time and temperature degradation factors for accelerated testing must

be justified against these minimal life usage conditions.

3.2.1.10 Wire bond integrity

. If pre-burn-in, interim and post burn-in electrical failures (opens/shorts), qualification, or

quality conformance inspection failures indicate questionable wire bond integrity then an analysis is required to verify the

bond integrity. If any bond is confirmed to be defective; the applicable inspection lot or sublot will be rejected, an evaluation

performed to determine the cause of the bond failure, corrective actions implemented based on the evaluation, and

disposition of other affected inspection lots or sublots. The failure analysis and corrective actions will be retained and made

available to the qualifying activity upon request.