How To Help The Gap Between Design & Production Test

How To Help The Gap
Between
Design & Production Test
Bert Horner
The Test Connection, Inc.
Rev 2.2
2013 PCB Carolina
Test Methodologies
Rev 1.2 10/30/09
Test (ATE)
VS.
Inspection (AOI or AXI)
•Test is the means by which the presence,
quality, or genuineness of anything is
determined; a means of trial.
•Inspection is official viewing or examination.
As You Can See….Test & Inspection Are Different
What Are The Most Common Faults On
Boards?
Manufacturing Testing
Electrical Test
ATE Comes In Different
Flavors….
In-Circuit Test
ICT
Flying Probe Test
Functional
Test
JTAG
Boundary Scan
IEEE 1149.1
Boundary Scan Test
AKA: JTAG - Joint Test Action Group
AKA: IEEE 1149.1
What Is It?
A standard specifying how to control and monitor
the pins of compliant devices on a printed circuit board.
Figure 1
Figure 2
JTAG (1149.1) Advantages
• Quick Test Development Time.
• Ability To Do In-System Programming (ISP) Of
Complex Devices.
• Using BSDL Tests That Were Already Developed By
Chip Mfg’ers.
JTAG (1149.1) Disadvantages
• Designers Need To Be Aware Of JTAG Design Rules.
(VERY IMPORTANT)
• Custom Cable Or Interface.
• BSDL Tests Need To Chip Mfg’ers.
• *Only Works With Digital Devices…No Analog
* National Semiconductor Does Have One Analog Devices
That Is 1149.4, But Not Being Used By Anyone.
In-Circuit Test (ICT)
AKA ‘Bed Of Nails’
Two Largest ICT Mfg’ers: Agilent 3070
(I3070)
& Teradyne (Formerly GenRad)
228X or TestStation
Digitaltest
MTS300
ICT or Bed Of Nails Use A Test Fixture
To Mate Up To Common Interface.
In-Circuit Test Fixtures
Not Ever Fixture Is Meant
For Every Test System
ICT
What To Look For…
-Probing
-Chip
Interconnectivity
Test Pads
Test Vias
Agilent Technologies Bead
Probe Technology
(See Handout)
ICT Advantages
• Automated Tester.
• Lower Level Operators Needed.
• Faster Test Times.
• Good Diagnostics.
ICT Disadvantages
• Expensive Tester.
• Cost For NRE Set Up.
• Needs a Fixture or Bed Of Nails Interface.
• Fixture Needs Maintenance.
Flying Probe Test
AKA ‘Fixtureless Test’
Want To See Them Move?
Flying Probe Advantages
• Minimalize Exposure - NRE Set Up.
• Faster Time To Production Ready Testing.
• Limited Or No Fixture.
• More DFT Lenient.
Flying Probe Disadvantages
• Slower Test Time.
• Electromechanical System (Regular Maintenance
Needed).
• With Age Of Systems, Separation In Technology.
• Systems Costs.
Functional Test
AKA System Test or ‘Rack & Stack Testing’
PXI
Considerations:
1) Documentation
2) Technology Used
3) Sustainability
4) Repeatability
5) Diagnostics
Bench top
Or Custom
VXI
Examples of BAD Functional Test
Figure 1
Figure 3
Figure 2
Can you guess
why?
Functional Test Advantages
•Parametric Testing.
•Operations/Functions Validated.
•Able To Be Used For Field Returns.
•PC Based Instruments.
Functional Disadvantages
•Manual Test Generation.
•Manual Test Procedures –
Documentation.
•Proprietary Product Knowledge.
•Higher Level Operators.
Methodology
Conclusion
Production test does add value to your
product. Why?
• Reduces expensive field returns.
•Diagnostics for production related
errors…..reduces troubleshooting time.
•Feeds process related information to
production.
CAD vs. GERBERS
(From A Test Engineering Point Of View)
Rev 1.2 03/20
CAD vs. GERBER
Is There A Winner?
CAD vs. GERBER
Why Is GERBER Not Good Enough?
Raw GERBER data is devoid of most intelligent
information used in manufacturing test such as
referenced designators, device body center (x/y),
device rotation and pin numbers.
“...GERBERS are a picture of the CAD…” Olaf Rohrbacher of Digitaltest
GmbH
CAD vs. GERBER
What & Why Is This Needed For Test?
•Device Body Center (x/y): Probe placement for
either flying or fixed probes. Needed for machining
of fixture. (A)
•Device Rotation: Probe placement for either flying
or fixed probes. (B)
•Referenced Designators: Failure information needs
to be called out to the lowest level (i.e. net and
component). (A)
•Pin Numbers: Failure information needs to be called
out to the lowest level (i.e. net, component and pin).
(B)
CAD vs. GERBER
What information is in the ASCII CAD?
1.
2.
3.
4.
5.
6.
7.
Location Reference.
X & Y Coordinates.
Theta (Part Rotation).
Part Number (Reference to BOM).
Package Style.
PCB Mount Side (Top or Bottom).
Component Technology (SMT or PTH).
ASCII CAD is not important…It’s VERY Important.
Looks The Same?
Gerber
CAD
Closer Look…..I See Differences
Gerber
CAD
CAD vs. GERBER
What does GERBER by us?
GERBER files is used by fixture vendor to set “push
down fingers” or “golf tees” to get the board in place.
They also us this information for vectorless testing.
The GERBERS are used to make the capacitive
plate of TestJet, Opens Xpress, and Opens Check.
TestJet or VTEP for Agilent
Opens Xpress or FrameSCAN for Teradyne (GenRad)
Opens Check for Digitaltest
Old Boards With No CAD….Now What?
No CAD, Only GERBERS….
There are tools that can be
used that used, but there is a
cost of time and money.
CAM350 and GraphiCode.
This process is called "Reverse Engineering". C-LINK doesn't
contain a software module which does this - because we advise
our customers to use native CAD data as input because this
faster. Translating CAD to a manufacturing test format can be
minutes verses 1-2 days using GERBERS.
If working with a larger board (1500 nets) that has a mix of THT
and SMT, it can be even more like 15 minutes compared to 5
Days. Because reverse engineering is a manual and time
consuming process, it’s not always error free.
CAD vs. GERBER
Who is the winner?
BOTH Are…..We need both CAD & GERBER.
“... I always ask for both, we need them…”
Joe Folsom of The Test Connection
More Practices for
Gaining Access and/or Cost
Cutting of
Production Test
Rev. 1,1
Fixturing Should be Kept To Probing to
One Side.
Sample is Agilent 3070
Sometimes We Need to Probe
Both Sides…Clamshell
Items to Consider:
1) Added Cost.
2) Time To Build.
3) Flipping the UUT?
4) Probing Tolerances.
5) Technology Used.
When Fixturing, Knowing the Limitations
The Lower
Limits are
Safer Limits.
NOT meant
for the entire
board.
Bottom side.
Make The Tester Successful….
 Pick a test solution that can be supported.
 Picking a interface that is “servable”.
 Have back up plan – 2nd or 3rd
Vendor.
 Document.
Things to Think About
Test, Inspection or Both?
What Faults Keep You Awake?
Types of Testers?
How to Interface?
Manufacturing Match Up?
Types of Data?
CAD Format?
Where to Probe?
Size of Probes?
Design For Test (DFT) Notes:
http://www.ttci.info/DFTRules.html
Questions?
Thank you for your time.
Bert Horner
[email protected] (410) 205-7300