Solving Today’s Test Challenges: Razor Sharp Probes · PDF fileedge. 90 º Primarily designed ... Razor on an OSP via, unpasted, no-clean process. Witness mark of a 6R-S ... “Typical

Solving Today’s

Test Challenges:

Razor Sharp Probes

QA Technology Company, Inc.

Test Challenges… Varietytargets, materials, finishes, processes

thru-hole leads

test pads

large via holes

ENIG Immersion Au (gold)

Immersion Ag (silver)

Immersion Sn (tin)

Organic Solderability Preservatives (OSP)

variety of solder pastes

variety of solder fluxes

wave soldering

select wave soldering

single reflow

double sided reflow

air vs. nitrogen (N2) atmosphere

small via holeshigher melting point

decreased solder flow rate

pasted (filled) via

pin-testable solder paste

unpasted (unfilled) via

no-clean

lead-free (Pb-free)

Failed


Effects of Test Challenges…

Slower Throughput

False Failures

“NDF” No Defects Found

Increased Cost Of Test

Unreliable Contact

Reduced Probe Life

Higher Spring Forces

Increase Board Flex

Fewer Probes

Reduced Coverage

Missed Defects

Bad Boards Pass The Test

$


Variety of Difficult Test Targets

OSP, Lead-Free Solder Pasted ViaOSP Copper Via, Unpasted

Lead-Free Solder Pasted Test Pad Lead-Free Dome of Solder


New Probe Design Challenge

To significantly improve probe contact

reliability on even the most difficult to

probe test targets.


Internal Test Vehicles (pcbs)

Board Mfg. & Provided by Major OEM

Processed at Multiple CM’s to OEM Spec’s

OSP Copper, Lead-Free, Pasted Vias (no-clean)

All Paste Stencils Were 6 mils Thick

Rows 1-16 = .010” hole, .030” dia.

Rows 17-32 = .012” hole, .035” dia.

Boards Processed in Both Air and Nitrogen (N2)

“Typical” Alpha Metals OM338-PT Pin-Testable

“Extreme Difficult” Alpha Metals OM338


Internal PCB Testing

Single Hit Per Target (First Pass)

32 Targets per Row, 691 Rows

2 second cycle time

22,112 Total Points / board = 20 min.

Vacuum Test Fixture

PCB Indexing Capability

Captures Resistance Test

Measurements

“Failure” was defined as resistance >

500 milliohms


The Solution…

RAZOR SHARP PROBE TIPS designed to contact Vias and Test Pads on boards manufactured with difficult to contact processes.

8R-S – 150° 6R-S – 90° 9R-S – 40°


Primarily designed to contact VIAS. The 8R-S, 150° angle contacts the face of a via, and reduces the chance of being blocked by a pool of flux in the center.

Also works well on flat test pads, but not solder “domes.”

8R-S Razor Sharp Tip Style

150º

Side view with 60º secondary angle.

Extremely

sharp cutting

edge.

Front View primary angle.


Witness Marks


Witness mark of an 8R-S Razor

sharp tip on lead-free pasted via,

no-clean process

Witness mark of an 8R-S Razor

sharp tip on lead-free pasted test

pad, no-clean process


8R-S Razor on Solder Dome



Extremely

sharp

cutting

edge.

90º

Primarily designed to contact VIAS & TEST PADS. The 6R-S,

90°angle improves electrical contact on filled, unfilled vias &

flat test pads. Having a steeper angle than 8R-S, they may not

work quite as well on filled vias.

Side view with 45º secondary angle.Front view primary angle.


Witness Marks


Witness mark of a 6R-S

Razor on a lead-free pasted

test pad, no-clean process.


Razor on an OSP via,

unpasted, no-clean process.


Razor on a lead-free

pasted via, no-clean

process.



Extremely

sharp cutting

edge.

40º angle

Primarily designed to contact TEST PADS & “DOMES” of SOLDER. The steep 9R-S, 40°angle creates a sharp center point that works well on test pads & solder “domes.”

Side view with 23º secondary angle.Front view primary angle.


Witness Marks


Witness mark of a 9R-S Razor

on a lead-free pasted solder

“dome”, no-clean process

Witness mark of a 9R-S Razor

on a flat lead-free soldered test

pad, no-clean process


SEM Photos of Razor Tips

8R-S Razor Face View 8R-S Razor Side View

61-S Typical Blade Side View 6R-S Razor Side View


Performance Testing – FPY“Typical Case” - Test Vehicles Identically Processed in Air

100mil Conventional - Pin-Testable Solder Paste

"02" Alpha OM338-PT, DSDR

97.395.794.4

83.5

99.798.498.193.8

100100100

91.5

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

3.5 (99) "L" Spring 5.5 (156) "S" Spring 6.5 (184) "H" Spring 8.1 (230)"Y" Spring

"Spring force is in ounces (gms) at 2/3 stroke"

Fir

st

Pa

ss

Yie

ld <

50

0M

illo

hm

s

61-S Blade 6R-S Razor 8R-S Razor


Performance Testing – FPY“Extreme Case” – Test Vehicles Identically Processed in Air

100mil Conventional - Difficult To Probe Solder Paste

"0S" Alpha OM338, DSDR

94.1

86.2

39.4

97.198.597.0

58.1

99.797.596.4

66.2

99.8

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

3.5 (99) "L" Spring 5.5 (156) "S" Spring 6.5 (184) "H" Spring 8.1 (230)"Y" Spring

"Spring force is in ounces (gms) at 2/3 stroke."

Fir

st

Pa

ss

Yie

ld <

50

0m

illi

oh

ms

61-S Blade 6R-S Razor 8R-S Razor


Beta Site Test ResultsIn three independent studies performed at two different CMs in China, the

Razor sharp tip style outperformed conventional probes with consistent and

reliable contact.

Beta Site 1Beta Site 2

(Reduced Spring Forces)

Beta Site 3(Reduced Spring Forces)

Conventional

Blade 8.1oz

Razor

8.1oz

Conventional

Blade 8.1oz

Razor

6.5oz

Conventional

Blade 8.1oz

Razor

6.5oz

1st Pass 55% 96% 82% 100% 11% 96%

2nd Pass 30% 4% 12% 17% 4%

3rd Pass 10%

0%

0% 4%

4th Pass 6% 0%

5th Pass 0% 4%

Total

Success Rate

95% 100% 100% 100% 36% 100%

Lead-Free Pasted Vias with No-Clean Process

Increased First Pass Yields, Faster Throughput, Lower Spring Forces…


Internal Life Cycle Testing

Condition of probes

after 58k cycles on

OSP, lead-free pasted,

no-clean processed

boards still performing

with single actuation.

Fixture

ActuationsCycle Life

Boards

Tested

Standard Steel

Blade5 60,000 12,000

Steel Razor 2 60,000 30,000

Longer Probe Life results in lower board test costs


Life Testing100mil 6R-S Razor Probe Life Test

New Probe

Same Probe after

67,900 cycles (flux has

been cleaned)

80%

85%

90%

95%

100%

Fir

st

Pa

ss

Yie

ld <

50

0m

illi

oh

ms

Total Cycles

Using TV's with Alpha OM338 and OM338-PT solder paste

and various processes.


Customer Feedback

1. Large CM in MexicoFPY: Start 40%, Razor Probes 88%. Comments: It is the best probe for any OSP process, pasted or non-pasted. It will be our standard probe for all OSP assemblies tested at ICT. Board throughput: Increased 68 to 93 boards per hour.

2. Mid Size CM in MexicoFPY: Start 85%, Razor Probes 92%. Comments: It improves the test contact on boards tested.

3. OEM in the USAFPY: Start 50%, Razor Probes 80%. Comments: I am extremely impressed with the Razor Probes.

4. OEM in MexicoFPY: Start 65%, Razor Probes 70%.

QA Technology has shipped Razors to over 130 customers.


Via “Damage Testing”Conventional Blade Tip vs. Razor Tip Style

8R-S Razor

61R-S Blade – 1 Hit

61H-S Blade – 20 Hits 6R-S Razor – 20 Hits

6R-S Razor – 1 Hit

8R-S Razor – 20 Hits

8R-S Razor – 1 Hit


Reduce Board FlexUse of lower spring forces reduce stress (shown in red) on board


Goal Achieved

Significantly Improved Probe Contact Reliability on Even the Most

Difficult to Probe Test Targets

New Razor Tip Design Results:

Fewer number of Fixture Actuations Required = Lower Board Test Costs

– Significantly reduces false failures (NDFs)

– Increases first pass yields (FPY’s)

– Achieves higher board throughput rate (reduces test time & retest rate)

– Extends probe life significantly

Reduces Board Flex

– Enables the use of lower spring forces under dense areas.

Improves Test Results

– Allows for tighter tolerances on component measurements

– Guarantees more stable digital tests


Care and Installation

Use of a plastic probe installation tool or

other plastic “pusher” reduces the risk of

tip and/or probe damage when installing

the Razor tip probes.


Availability


Thank you.

Documents

Solving Today’s Test Challenges: Razor Sharp Probes · PDF fileedge. 90 º Primarily designed ... Razor on an OSP via, unpasted, no-clean process. Witness mark of a 6R-S ... “Typical