CheckSum pneumatic and mechanical test fixtures are rugged, reliable and inexpensive-especially when compared to the heavy vacuum fixtures required by traditional in circuit testers.
CheckSum fixturing is compatible with all of CheckSum’s test systems. Since the electronics are isolated from the fixture you can use CheckSum’s factory-built fixtures or build your own special fixturing or adapters that can accommodate ribbon-cable connectors.
CheckSum can provide fixture kits for your customization or do the complete fixturing and test programming job for you.
Call or e-mail us for a quotation on your next project.
Review the Information Required to Quote and Build Test Fixtures
CheckSum Fixture Selection Guide for EU Member States
CheckSum Fixture Selection Guide for non-EU Member States
Read the FAQs about Fixtures
List of Test Fixture and Spring Probe Suppliers
Model 12KN Dual Level Long-Travel Pneumatic Fixture System
The 12KN Dual Level Pneumatic Fixture System is integrated into a rack-cabinet and designed to be the basis for CheckSum bed-of-nails test systems. The long-travel press eliminates the need to open and close a lid between tests. The fixture kits are easily changed by sliding the fixture top plate and base into place. The system uses a universal spring-probe fixture interface. The fixture system can accommodate up to 5200 test points and uses standard CheckSum fixture kits. Integrated into the system is rack space for system electronics and an operator keypad with a minimum selection of buttons to make it easy, safe, and error-free for the operator to use. The 12KN is compatible with existing CheckSum KIT1000-QC and KIT2KN-QC fixtures. A safety light curtain provides operator safety.
Fixture Guidelines: Assembly size can be up to (approximately) 24 x 13.2 inches (61 x 33.5 cm), dual level, single-sided and double-sided probing plus TestJet.
Model TR-7-1000-QC Pneumatic Fixture SystemThe TR-7-1000-QC is a new version of our popular TR-7-1000 pneumatic fixture receiver. Uses air pressure to press the assembly being tested onto spring probes. Usable to 1000 test system connections, the Model TR-7-1000-QC is ideal for most testing applications including dual-level fixturing. Using low-cost removable fixture kits, it can accommodate assemblies where adding a vacuum seal is difficult.
Fixture Guidelines: Assembly size can be up to (approximately) 16 x 13.2 inches (40.6 x 33.5 cm), dual or single-sided probing and TestJet.
Model TR-5-400-QC Mechanical-Advantage Fixture System
Designed for test fixturing of assemblies with up to 400 test points. The Fixture System consists of a reusable Fixture Press that is used in conjunction with low-cost, easily interchanged Fixture Kits.
Fixture Guidelines: Assembly size can be up to (approximately) 11.75 x 8.5 inches (30 x 21.5 cm), dual or single-sided probing and TestJet.
Model TR-5 Mechanical Bed-of-Nails Fixture Kits
Uses mechanical pressure from the operator to press the assembly being tested onto spring probes. Usable to about 150 test system connections, the Model TR-5 is well suited for applications where vacuum is not available, to minimize cost, or for assemblies where vacuum sealing is difficult.
Fixture Guidelines: Assembly size can be up to (approximately) 14 x 14 inches (35.5 x 35.5 cm), bottom-side probes only.
TR-3-Console Vacuum Bed-of-Nails Fixture System
Console setup for system test electronics to accept industry-standard GR-2270 style test heads with up to 1500 test system connections. Automatic vacuum control and vacuum gauge. Connects to your vacuum source.
Fixture Guidelines: Assembly size can be up to (approximately) 21 x 17 inches (53.3 x 43 cm), single-sided probing and dual or single-sided TestJet.
TR-3A Bench-Top Vacuum Bed-of-Nails Fixture System
Bench-top setup to connect system test electronics to industry-standard GR-2270 style test heads with up to 1500 test system connections. Automatic vacuum control. Connects to your vacuum source.
Fixture Guidelines: Assembly size can be up to (approximately) 21 x 17 inches (53.3 x 43 cm), single-sided probing and dual or single-sided TestJet.
In working with our customers, we have found there are some common questions about bed-of-nails fixturing and test systems. Here are some general guidelines to consider when planning for your test fixture. If you have any questions, call us, we would be happy to discuss your testing needs. Be sure to ask to expedite your job for a faster turnaround.
Fixture FAQs Document (14 pages)
Contents
* Bed-of-Nails Basics
* Customizing the Fixture
* Providing Pneumatic Air Pressure (Analyst / TR-9 / TR-7)
* Providing Vacuum (MultiWriter pps / TR-3 Series)
* Miscellaneous Questions
* Custom test fixtures and test programs from CheckSum
* Fixturing Supplier Source List
* Spring Probe Vendors List
Q. How do „bed-of-nails” fixtures work?
On a bed-of-nails „fixture” or „test head”, the unit-under-test (UUT) is forced onto a number of spring probes („nails”) that are electrically connected to the test system. The test system can then make measurements between these points.
Q. How is the UUT forced onto the nails?
On pneumatic test fixtures, such as the CheckSum Analyst, Model TR-7, and TR-9 series, compressed air pressure and pressure/push rods are used to press the UUT onto the spring probes. On vacuum fixtures, such as CheckSum’s Model TR-3 series, vacuum is used to pull the UUT down onto the probes. On mechanical test fixtures, such as CheckSum’s Model TR-5, the operator presses the UUT down onto the probes via the force of closing the top cover, with pressure/push rods, down on the UUT.
Q. What are the major elements of mechanical, vacuum, and pneumatic fixture systems?
On the TR-5 mechanical fixture, the entire fixture is dedicated for a UUT. The test point electronics from the test system plug into the back of the fixture. On the TR-5-400 / TR-5-600 mechanical-advantage, TR-3 series vacuum, and Analyst / TR-7 / TR-9 pneumatic fixtures systems, there is a fixture receiver (or press) which is shared by all of your UUTs, then a customized „fixture” (or „test head”) is built for each different UUT. The customized test head in the fixture receiver or press is easily changed.
Q. How do I choose between vacuum, pneumatic and mechanical fixtures?
Q. How big a board can I put on a test fixture?
The various size guidelines are shown below. Slightly larger boards may also fit, depending on where the test probes must be positioned with respect to the UUT.
12KN Dual Level Guidelines
KIT28, KIT20, KIT2KN-QC or KIT1000-QC Fixtures: Assembly size can be up to (approximately) 24 x 13.2 inches (61 cm x 33.5 cm), dual or single-sided probes and TestJet.
TR-9-2000-QC Guidelines
KIT2KN-QC or KIT1000-QC Fixtures: Assembly size can be up to (approximately) 16 x 13.2 inches (40.6 cm x 33.5 cm), dual or single-sided probes and TestJet.
TR-9-1000-QC Guidelines
KIT1000-QC Fixtures: Assembly size can be up to (approximately) 16 x 13.2 inches (40.6 cm x 33.5 cm), dual or single-sided probes and TestJet.
TR-7 Series Guidelines
KIT1000-QC, KIT2000-QC or KIT3000-QC Fixtures: Assembly size can be up to (approximately) 16 x 13.2 inches (40.6 cm x 33.5 cm), dual or single-sided probes and TestJet.
TR-5-400-QC and TR-5-600-QC Guidelines
KIT600-QC Fixture Guidelines: Assembly size can be up to (approximately) 11.75 x 8.5 inches (30 cm x 21.5 cm), dual or single-sided probes and TestJet.
TR-5-812 Fixture Kit Guidelines: The kit is 8 x 12 inches (20.3 cm x 30.5 cm) overall and can accommodate an assembly size up to (approximately) 6 x 6 inches (15.24 cm x 15.24 cm) with bottom-side probes only.
TR-5-1216 Fixture Kit Guidelines: The kit is 12 x 16 inches (30.5 cm x 40.6 cm) overall and can accommodate an assembly size up to (approximately) 10 x 10 inches (25.5 cm x 25.4 cm) with bottom-side probes only.
TR-5-1620 Fixture Kit Guidelines: The kit is 16 x 20 inches (40.6 cm x 50.8 cm) overall and accommodates UUT sizes up to 14 x 14 inches (35.5 cm x 35.5 cm) with bottom-side probes only.
TR-5-1612-C Fixture Kit Guidelines: The kit is 16 x 12 inches (40.6 cm x 30.5 cm) overall and accommodates UUT sizes of up to 13.5 x 8.5 inches (34.3 cm x 21.6 cm), dual or single-sided probes and TestJet.
TR-3-2024 Fixture Kit Guidelines: Assembly size can be up to (approximately) 21 x 17 inches (53.3 cm x 43.1 cm), single-sided probes and dual or single-sided TestJet. Smaller vacuum fixture kits are available for smaller boards.
Q. What is involved with customizing the test head for a particular assembly that I want to test?
There are several steps. You start with a mechanical fixture kit (e.g., CheckSum’s Model TR-5-1216), a pneumatic fixture kit (e.g., CheckSum’s Model KIT1000-QC) or a vacuum test head kit (e.g., CheckSum’s Model TR-3-1620), then the steps below are done:
Q. Does the customized part of the fixture have to be done by CheckSum?
No, there are many fixture vendors.
Q. Can I build my own fixtures?
With the proper equipment (e.g., a way to accurately do the drilling), fixtures can be built by the end-user. However, it does require special expertise in many cases to solve some of the problems that can occur. For that reason we recommend that you have at least one fixture built by specialists to serve as an example. You can also contract some of the job, like drilling, then do the wiring yourself.
Q. To test my board, how many probes are required?
Generally, one probe is used for each electrical network (node). As a result, there will be many less probes than there are holes in the board; the node-count is generally about a third of the hole-count. Optionally, you can install extra probes to power supply networks and to very low-impedance value components to help facilitate external sensing of measurements for highest accuracy.
If you want to confirm open connections in PCBs, you will need to use more than one probe per network. This is seldom done in practice since most PCBs are tested prior to assembly and opens typically aren’t caused during the assembly process.
Q. What kind of spring probes should I use?
There are many styles of probes available; many with special attributes for particular applications. The most commonly used probes are some variation of a crown style or chisel style with contact forces of about 6-10 ounces per probe.
Consult the spring probe manufacturers for recommendations on head style and spring force.
Q. Is there anything special to tell a fixturing facility about how to wire a CheckSum test head?
Make sure that they have a copy of CheckSum’s wiring conventions (block and connector nomenclature and pin numbering scheme). We will provide this information directly to the vendor if you wish. For GenRad-style vacuum fixtures, the test head is oriented with the interface towards the operator, so the UUT orientation is generally reversed from GenRad fixtures.
If you are fixturing for functional test, there are some special wiring considerations. See the Model FUNC-2 Instruction Manual for details.
Q. How large must the vacuum test head be?
The outside dimensions of the test head need to be at least 3 inches (7.6 cm) larger than the UUT (1.5 inches, 3.8 cm, all around). The most popular sized vacuum test head that CheckSum sells is the TR-3-1620, 16 x 20 inches (40.6 cm x 50.8 cm) overall. Both smaller and larger test heads are available. CheckSum lists the sizes of our test heads in overall size. Some other manufacturers list the working area. Make sure to ask the supplier if there is any question about their dimension conventions.
Q. I need a small amount of special circuitry to help test my UUT. Can this be accommodated?
There is sufficient room in most test heads to accommodate internal circuits like relays or breadboards. CheckSum offers the Model TR-6-2 Interface Module especially designed for this use.
Q. I will be testing surface-mount boards. Can they be used with a bed-of-nails fixture?
For the lowest cost fixture, lay out the PCB so that there is access from one side of PCB to at least one point on every network (net). Careful placement of through-holes can usually provide this. With this layout, you can test using a standard test head. Recommended target pad size is .035 inches (0.89mm) or larger. If you require probe access to both sides, special double-sided fixtures can be built. Double-sided fixtures are very common with SMT boards however they are more expensive. See the following reference at the SMTA web site for DFT guidelines: http://www.smta.org/store/book_detail.cfm?BOOK_ID=176
Q. My UUT has test points on both sides (top and bottom). Can CheckSum probe both sides of my UUT?
CheckSum has been making dual-sided “clamshell” test fixtures for many years. Our pneumatic fixtures and presses are well suited for top probing of fixtures. For top probing, it is important to provide good size test pads for better probing accuracy.
Q. Are there any other PCB layout considerations?
Fixturing is more reliable and less expensive if holes are on 0.1 inch (2.54 mm), or greater, centers. Probes are available for closer spacing, but the fixturing job is more difficult since closer positioning tolerances are necessary, and the probes are more expensive. The 50-mil and 75-mil probes are very common on the high-density SMT boards we see today. Also, for vacuum fixtures, keep component leads at least 1/8 inch (3.175 mm) from the board edges.
Providing Pneumatic Air Pressure (Analyst / TR-9 / TR-7)
Q. What kind of air supply is necessary for pneumatic fixturing?
Standard factory air can be used in most cases. The fixture operates from 80-120 PSI. Use of a standard regulator/filter near the test system is recommended.
Refer to the specific fixture system manual. The higher force spring probes will require greater force to fully-compress. This may require the maximum air pressure; 120 PSI for some test fixtures.
Providing Vacuum (MultiWriter pps / TR-3 Series)
Q. How much vacuum do I need?
Most vacuum test heads require about 20 inches of mercury (67.75 kPa) with a 20 gallon vacuum surge tank (vacuum reservoir) to work properly. Pumps with this capacity are generally 1.5 HP and larger.
Q. Does my particular UUT affect the amount of vacuum needed?
Yes. UUTs that have many probes per square inch of PCB area may require more vacuum force. Generally, vacuum requirements start to become more critical if the average probe loading of your UUT exceeds about 10 probes per square inch of PCB area. Also, if your UUT has openings that can’t be sealed with a gasket (e.g., open vias or routes), or if it has unsoldered through-holes, it may require more vacuum CFM capacity.
Q. Does it help to get a bigger pump?
Since the incremental cost of purchasing a larger pump is relatively small, we recommend getting one bigger than you need. That way, if you add systems in the future and want to share a pump, or if you have a problem UUT requiring additional capacity, you will be ready.
Q. Is a vacuum pump all I need?
You should also have a vacuum surge tank to accommodate the initial vacuum requirement when pulling the UUT down to the fixture.
The vacuum hose connected to the MultiWriter pps or TR-3 series should be large enough to quickly and completely pull the board down on the spring probes.
If the vacuum source is not sufficient, when the vacuum is applied the UUT will not be pulled-down quickly. It needs to be quickly pulled-down to create a vacuum under the UUT to seal the UUT with the gasket. As the UUT moves down, it will compress the spring probes that need to firmly contact the UUT.
Q. Are there alternatives to the surge tank?
Some facilities use large PVC tubing (e.g., 2 to 3 inches, 5 to 7.6 cm, diameter) for plumbing the vacuum system. If properly designed, this can effectively serve as a surge tank.
Vacuum surge tanks are generally 10 gallons or larger.
Q. Can I buy the vacuum pump from CheckSum along with the system?
CheckSum can sell you a vacuum pump along with your system. However, you can save money by buying it directly from the manufacturer. If purchased from CheckSum, we will have the manufacturer ship it directly to you.
Q. Can you give a recommendation for a vacuum system?
Most ATE systems use Busch brand vacuum pumps. An example of a complete 28 CFM system with motor, pump, tank, filters, hose, skid and casters is the Busch BMV-040-0. A similar 20 CFM system is Busch’s model number BMV-025-0. Busch pumps use 3-phase power.
Q. How much does a vacuum system cost?
For a typical installation, you should plan on about $2500 to $3500 for a vacuum system.
Q. I’ve got a bunch of fixtures for my old worn-out system that was made by *%@!#!*%*. Can I use them?
There is nothing unique about CheckSum testers that makes fixturing special. If you can adapt your existing fixtures to mate with the 50-pin ribbon cables from the CheckSum System, you’re in business. Fixture manufacturers (or CheckSum) can also build adapters from one type of fixture to another type of receiver.
The Analyst fcs (fixture compatible series) is specifically designed to accept Agilent 1, 2 and 4 module 3070 style fixtures. The test system software includes a test program generator to automatically create the CheckSum test program using existing 3070 data files.
Q. Is there a way to take advantage of the CAD data I have to help with fixturing and programming?
Yes. CheckSum provides CAD conversion capabilities with its in-circuit test systems. Also, third-party software packages can help lay out the fixture and provide an initial test program. Please review our document on the Information Required to Quote and Build Test Fixtures.
Q. My UUT is not designed for test. Can CheckSum probe on SMT components to improve my test coverage?
Probing on components is a risky practice. The only way to probe SMT parts directly is to probe on the solder fillet. This presents (3) main problems:
It is CheckSum’s practice not to probe on components. Please review our design for test document.
Q. I have multi-board panels. Can these be tested before separation?
Yes. They are fixtured just like a single assembly. It you arrange the wiring properly, CheckSum in-circuit test systems allow you to create the test program for the first PCB on the panel, then automatically replicate the test for the remainder of the PCBs. The system also automatically separates test results as appropriate, allows you to skip particular PCBs on the panel, and shows which PCB is being tested.
With panelized PCBs, it is good practice to also provide a single test position to accommodate testing assemblies after separation after they have been repaired.
Please include drawings that show the dimensions for each separate board on the multi-board panel. We need each board’s specific XY information to position the spring-probe and guide pin locations.
Custom test fixtures and test programs from CheckSum
CheckSum can do custom programming and fixturing for you. We recommend that you have us build your first fixture and write the test program used with it to serve as an example and to make sure that you are up and operating right away. Many of our customers continue to have us build their fixtures and write their test programs on an ongoing basis. Call us for a quotation for your next CheckSum fixture project.
Q. If I am going to have a test head built, what do I need to provide?
You will need to provide complete CAD* information (ASCII full CAD output, gerber files and a drill file), a mechanical drawing that calls out board dimensions, a schematic, a BOM (Bill of Materials) an assembly drawing showing component placement, a bare-board, and a loaded-board.
*Note: Jobs can be processed without full CAD data in some situations, but the costs are much greater and the lead time is increased. If you also provide information directly showing the XY position of each probe and an associated net-list or annotated schematic, it reduces the cost of the job.
Q. I plan to write the test program, can you give me a budgetary cost estimate for building a custom bed-of-nails fixture for my assembly?
The cost varies, but here is a rough idea of what to expect:
Test fixture kit: $610 – $870
Drilling, file-processing, machining: $750
Wiring connectors: $10 per 50 probes
Probes, sockets, layout, wiring: $3.00 – $6.00 each
Based on this, here is a general idea of what you might expect to pay for mechanical or pneumatic fixtures of various sizes (assuming only 100-mil probes are required):
100 Test points: $1,850
250 Test points: $2,300
500 Test points: $3,500
Vacuum fixturing costs are similar, but higher. With additional vacuum sealing costs and higher fixture kit costs, typical vacuum fixtures are about $1000 more than the alternatives shown.
Q. If CheckSum is going to write the test program, is there anything else I need to provide?
We need at least 2 or 3 (the more the better) known-good sample assemblies to validate the test program. After programming, we run statistical analysis on all the assemblies to help determine proper test tolerances to accommodate typical UUT-to-UUT and measurement variations. If you have compatible CAD data for the UUT (netlist and component values), it can be used to reduce the cost of programming.
Q. Can you give me a rough idea of how much it will cost to have CheckSum write the in-circuit test programs for my assemblies?
In-circuit test programming charges vary depending on the type of circuitry and node-count. The minimum programming charge is $600 ($300 for Opens/Shorts only).
Here is a general idea of the cost for a complete turn-key test fixture which includes the in-circuit test program for various test point counts:
100 Test points: $2,500
250 Test points: $4,000
500 Test points: $6,000
For panels with duplicate boards the programming cost goes down significantly.
Q. Does TestJet Technology drastically affect the costs of my fixtures?
Installed TestJet Technology probes cost about $100 per tested component. There usually is an additional fixed charge of about $450 for the top-access assembly that positions the probes. Note that CheckSum’s TestJet Technology implementation does not require a multiplexer to be built into every fixture. That is part of the test system.
Q. What are some of the things that affect fixturing/programming costs?
Q. Does CheckSum do this work for „time and materials”, or can I get a quote?
We do most of our work on fixed-price quotations. To give you a quotation, we need to know the probe-count (available from a net-list), any special probe spacing requirements (usually not a problem on through-hole or designed-for-test SMT boards), the UUT size, and the type of circuitry (digital vs. analog as shown in a schematic). If you provide us with this information we can usually give you a quote within 24 hours.
Q. How long does it take CheckSum to build a custom test fixture and test program for my UUT?
Standard lead-time is three to four weeks from the time we get your order and UUT materials. We can often do a faster turn around if you are willing to pay expedite fees.
Q. Is there anything special about the mechanical design of PCBs that will be bed-of-nails tested?
There are a number of things that you can do to optimize test coverage and fixture reliability while minimizing cost.
Q. Can CheckSum start my job without a loaded assembly?
To insure the fixture matches your assembly, we need a loaded assembly before we start the process. Ask for our paper on Design and Building Custom Test Fixtures for details about what we need for quoting and building your test fixtures. We can provide quotations for fixtures with or without a test program. In some instances, it is possible to get started with a new revision bare board, the most recent revision loaded board, and a list of the affected changes between the revisions. CheckSum will need to review the two (2) boards to determine if the job can be scheduled. You will still need to provide the current revision loaded board by a specified date to have your fixture and test program fully optimized.
Boundary-scan (also called “JTAG Test” after the Joint Test Action Group which developed the technique in the late 1980s) provides a means to test interconnects between integrated circuits on a circuit board “virtually” without using physical test probes.
Despite its promise to reduce testing cost, the added cost of designing boundary-scan circuitry into semiconductor devices has hindered its widespread adoption for a number of years.
However, the increasing density of boards and fine pitch components such as BGAs has significantly diminished the physical accessibility required for in-circuit test. As a result, boundary-scan is growing in popularity as it counteracts the loss of electrical access, increasing fault coverage on the small and very dense boards that are a feature of handheld products such as phone handsets and portable entertainment electronics.
While there are some boundary-scan circuit designs that can effectively eliminate the requirement for in-circuit test, the vast majority of boards still require in-circuit testing, with boundary-scan acting as a vital tool to increase overall fault coverage of the board. In one case, boundary-scan resulted in a 30% increase of fault coverage.
The major advantage of boundary-scan is that no knowledge of actual device function is required to perform thorough interconnect testing. Boundary-scan eliminates the cost and time required to develop and debug traditional digital vector test routines such as those required for ‘backdrive’ in-circuit test.
Boundary Scan Theory of Operation
The IEEE 1149.1 standard specifies the method, hardware and software parameters required to test interconnects among scan devices mounted on a printed circuit board (often called Boundary In-Circuit Test).
To comply with the IEEE 1149.1 standard a boundary-scan chip requires boundary-scan cells at each pin of the device. Each cell is basically a multiplexer and latch. The boundary-scan cell is shown as a small box at each pin in the diagram at right.
In ‘boundary-scan mode’ the latches at each pin are connected serially in a “scan path” (also called a “scan chain”) such that a data pattern is shifted into the latch at each pin via the “TDI” (Test Data In) pin.
Captured test data is serially shifted out via the “TDO” (Test Data Out) pin where it is read by the tester and compared to the expected results.
The Test Access Port (TAP) controller provides the necessary logic to switch the device into and out of ‘boundary-scan mode’ and control the overall test sequence.
Three control lines (TMS, TCK, TRST) perform these required functions in boundary test mode
The second half of the boundary-scan equation is the software required to:
Most available boundary-scan tools provide rigorous algorithms to stimulate and detect faults and to isolate faults to specific nets, devices, and pin numbers. The majority of these tools employ the Boundary-scan Description Language (BSDL). BDSL specifications were added to the IEEE 1149.1 standard in 1994.
A variety of boundary-scan tool vendors supply boundary-scan stimulus/measurement software and hardware adaptor tools, which can be added to any CheckSum Analyst system.
Low Cost Partnership Case History: Boundary Scan and Analyst In Circuit Test
A major contract manufacturer sought a way to implement boundary scan for a new board it was building but saw no point in purchasing an expensive traditional in-circuit tester such as those from Teradyne or Agilent just to obtain boundary scan capability. CheckSum provided a low-cost boundary scan test solution for under $70,000, including the cost of the Analyst ems in-circuit tester and boundary scan tools from a popular boundary scan technology supplier.
The circuit board was approximately 5 inches by 11 inches (12.7 x 17.8 cm) with 1,200 electrical nets, of which only 810 could be physically probed and tested using conventional ICT techniques. As is typical with modern devices, speed and functional complexity precluded using traditional vector-based ‘backdrive’ testing.
By adding boundary scan test, the contract manufacturer upped the total to 1,050 tested nets, boosting fault coverage from 68% to 88%–a 30% increase. In addition, the board included 40 ICs, the largest being an 860-pin ASIC. All of them were testable with boundary scan.
One-time charges were approximately $55,000 for the Analyst tester and $15,000 for the third-party hardware and software. Recurring costs of test for similar boards requiring boundary scan test would be only about $12,000 for the bed-of-nails test fixture in-circuit program and boundary scan test.
Boundary Scan Can Reduce Board Test Costs
A major goal of boundary scan test is to reduce test cost while maximizing test coverage. This contract manufacturer understood that implementing boundary scan on a traditional ICT contradicted the cost and simplicity goal of boundary scan. The CheckSum Analyst low cost in-circuit tester, on the other hand, is consistent with those objectives.
Roll your mouse over the topics in the column at the right for a quick review of testing techniques for ICs on boards, their advantages and disadvantages.
Testing ICs on Circuit Boards (In-Circuit Test): a brief tutorial
Delivers High Fault Coverage for the Least Cost
Opens around ICs–whether pins or internal problems–are the most prevalent fault class on virtually every SMT manufacturing floor. If you’re in circuit testing boards but skipping vectorless test you’re either wasting money, adversely impacting board quality–or both.
Power-off vectorless test is superior to classical digital vector test (aka „backdrive” test) in just about every IC testing situation. And TestJet is the most widely used vectorless test technology in the world.
But if you’re still using traditional 'big iron’ in circuit testers like Agilent and Teradyne to program and perform vectorless test you’re spending too much. Why?
Why CheckSum Analyst systems are your best tool for TestJet vectorless test
CheckSum Analyst systems use exactly the same TestJet Technology originally introduced by Hewlett-Packard (now Agilent) in 1994 and now used on thousands of in circuit testers worldwide. TestJet Technology reliably identifies opens around (and inside) almost any IC package with a lead frame or metallic pins or leads to which the TestJet probe can capacitively couple–an enormous variety of device types.
| Device Type / Package |
Use TestJet Technology? |
|
| Devices with an internal lead frame (most digital and hybrid devices) | Yes | |
| Devices with an internal ground plane (usually ceramic packages) | No | |
| Most Ball Grid Arrays (BGAs) (except ceramic and stadium packages) | Yes | |
| Some Ball Grid Arrays (CBGAs) (ceramic and stadium packages only | No | |
| Connectors and sockets | Yes | |
| Devices with grounded heat sink | No | |
| Flip chip devices or chip-on-board | No | |
| DIP switches | Yes | |
| Pushbuttons | No |
TestJet Technology is the ideal match to Analyst’s low cost and ease of application. Unburdened by expensive digital vector hardware and software, Analyst systems equipped with TestJet Technology create an unbeatable combination of low applications (fixture and test program) cost, fast throughput and high fault coverage.
The inside story: TestJet Technology
TestJet Technology examines the connectivity from each pin on a device to the circuit board. It does not require that power be applied to the device under test.
The TestJet hardware measures the capacitance from a pin of a device to the TestJet probe. The measured value is compared against preset limits by the Analyst system–just like any other in circuit test. If the capacitance falls below the lower tolerance an open pin exists. This measurement is repeated for each pin on the device except power and ground pins. Pins that are tied together are tested as one pin.
A specific test step is accomplished by connecting a low voltage AC stimulus source to the pin being tested, the Sense to the TestJet probe, and then to guard out (ground) all other pins on the device. The signal is amplified and filtered right at the TestJet probe to improve signal quality. Each TestJet probe is connected to a port on a system TestJet board that is mounted in the test system chassis. Depending on the specific test system configuration, up to 384, or more, TestJet probes can be connected to the test system.
Features
Application
Programming CPLDs (Complex Programmable Logic Devices) such as serial flash memories and microcontrollers after these parts have been mounted on the printed circuit board. Since the contents of Phase Change Memory (also known as PCM, PCME, PRAM, PCRAM, and C-RAM) can be lost because of the high temperatures needed to solder the device to a board, on-board programming is required.
The MultiWriter pps™ on-board gang programming system uses proven, patented simultaneous programming technology to program up to 384 chips simultaneously, up to 16 different types or families — typically in seconds instead of the minutes required by conventional programmers.
Compared to other part programming solutions, MultiWriter pps delivers significant speed and cost advantages over conventional in-circuit tester-based programmers when more than four parts already mounted on circuit boards must be programmed in a single pass, making it especially effective for multi-board panels.
MultiWriter pps is optimized for applications requiring programming of at least 4 parts per board or multi-board panel. MultiWriter can simultaneously program parts on multi-board panels with 10, 20 or more boards per panel.
Advantages of On-board Part Programming with the MultiWriter pps
Product Details
The MultiWriter pps On-board Gang Programming System includes:
Purchase or Pay-Per-Use
Is Pay-Per-Use the right solution for your programmed parts?
† MultiWriter Technology is protected under U.S. Patent No. 7,802,021.
Analyst In Circuit Test Systems
High-coverage In Circuit Test (ICT)
The CheckSum Analyst ems is designed to test all types of circuit assemblies. The system combines manufacturing process testing with TestJet Technology to test a single assembly or a panel of multiple assemblies.
MultiWriter Part Programming
In Circuit On-Board Part Programming
On-Board, Production Part Programming for up to 384 devices simultaneously means high-throughput at low cost.
Test fixtures
Reliability at low cost
Reliable low-cost test fixtures from CheckSum.
Turnkey support
Custom fixtures & test programs
Only CheckSum offers complete ready-to-run turnkey applications packages so your boards are in production fast.
New Circuit Board Technology Requires New Strategic Thinking
Circuit board technology evolves rapidly: more highly integrated devices, increasing package pin counts, denser placement of smaller components and thinner circuit traces. For boards ranging from simple to complex, the test and inspection process remains as critical as ever. Bad parts still find their way onto boards. Assembly and soldering defects still occur. In-circuit test (ICT) is still the most cost effective means to identify component faults and manufacturing process defects. And as long as there are circuit boards, ICT will continue to be the key to effective manufacturing process test.
But evolving technology requires a complete rethinking of in-circuit test strategy—and about the in-circuit tester itself.
Traditional ICT capabilities are increasingly expensive—and unnecessary
The Fault Spectrum Shift has basically negated the cost effectiveness of traditional ICT testers such as the Agilent 3070-series and Teradyne TestStation. Capabilities found on these testers such as high-accuracy analog and digital vector test are increasingly superfluous because they are designed to test for faults that rarely—if ever—occur on today’s boards. In fact, traditional digital vector test is ineffective on today’s complex, highly integrated devices. And newer assembly defect classes such as cold solder joints and skewed components are simply invisible to in-circuit testers and must be diagnosed by other means such as automated imaging (AOI, AXI).
Evolving technologies aren’t the only reason you should reexamine your ICT strategy and equipment. Today’s smaller test departments and constrained budgets demand lower ICT costs. In a fixed budget environment every dollar you spend unnecessarily on ICT means a dollar that you can’t invest in new inspection technologies like AOI and AXI.
The Low Cost ICT strategy
Seeking a lower-cost ICT strategy demands that you examine not only the purchase price of the tester, but also ongoing operating and applications cost, such as fixturing, programming, and support. Keep in mind that no matter how low the purchase price, “big iron” ICT still has high overhead costs from complex test fixtures and lengthy test programming processes—even when built-in capabilities like vector testing are not even used.
The good news about new board and parts technologies and the resulting Fault Spectrum Shift is that much lower cost ICT systems will do the job as effectively as old, expensive ones. That’s where the CheckSum Analyst Low Cost In-Circuit Testers come in. Check them out and see how CheckSum can reduce testing cost and help increase manufacturing margins.
Analyst ems 12KN
High-coverage in circuit test
Capable. Flexible. Straightforward. The CheckSum Analyst ems combines comprehensive manufacturing process testing with TestJet Technology for low cost in circuit test of today’s complex boards.
Analyst ems+ft 12KN
In circuit and functional test
The Analyst ems+ft combines all the in circuit capability of the Analyst ems with versatile power-on functional test, including relays capable of switching up to 250VAC (rms), full DMM, function generator and counter-timer for simple test routines to full functional test sequences.
Analyst ems TR-3-Console
Vacuum-based in circuit test
The Analyst ems TR-3-Console is an integrated rack/console system with vacuum-based fixturing.
Analyst ils
In-line in circuit test
The Analyst ils integrates the in circuit testing capability of the Analyst platform into an automated in-line board handling system–at a price less than many manually operated in circuit testers.
Analyst ems
In circuit test
The Analyst ems can be integrated with desktop pneumatic or mechanical type fixture systems. These low-cost test and fixture systems require a small space.
Founded in 1987, CheckSum has been delivering reliable, cost-effective, and flexible in-circuit test and on-board, in-system programming solutions to OEMs and contract manufacturers (CM). With an installed base of over 3,000 test systems at more than 200 manufacturing sites in over 40 countries, CheckSum’s customers range from automotive electronics manufacturers to global EMS / CM providers.
CheckSum’s practical production test and on-board, in circuit, part programming solutions help its customers reduce total test and manufacturing costs and increase profit margins.
Read these customer case histories and newsletters to see how CheckSum delivers solutions that meet the demanding technical requirements while reducing total cost:
Tier 1 Contract Manufacturer Cuts Programming Cost by 66%
On-Board Part Programming with Pay-Per-Use
How One Manufacturer Slashed
In-Circuit Test Cost by 60%
CheckSum’s Analyst Works
Side-By-Side with ’Big Iron’ In Circuit
Testers at a Fraction of the Cost
An OEM finds the Analyst is the
Ideal Platform for Boundary Scan
Test and High Throughput In Circuit
Part Progamming
Contract Manufacturer (CM) Implements
Boundary Scan Test on a New Board with
CheckSum’s Analyst In Circuit Test System
Fault Coverage Improves 30%
Managing Your Tester Portfolio and
Achieving a Low Cost Board Test Strategy
Many test engineers seek to „standardize” on a single brand or model in circuit tester. Intuitively, this makes sense: only one vendor to deal with, common fixturing, a single programming environment, simplified support. In order to deal with any board of any complexity, it seems to also make sense to standardize on traditional high-end in circuit tester that has all the reserve horsepower–high accuracy analog, sophisticated digital backdrive, functional test facilities, etc.–that the test engineer might ever need.
ICT Platform „Standardization” Means Higher Cost of Test
But traditional „big iron” ICT always drives up overall test cost–even when it’s the „standard” that’s supposed to reduce overall test cost. The theoretical savings of a “standard” rarely offsets the high fixturing, programming and support costs that traditional ICTs entail. A high capability tester is absolutely right for a high complexity board. But putting a simpler board on a „big iron” ICT is analogous to planting a rosebush with a backhoe: The job gets done, but it’s a lot more complicated and expensive compared to putting the less complex board on a less complex tester that has lower application and support costs.
Tester Portfolio Management is Straightforward
Just as a portfolio manager maximizes investor return by using a variety of investment vehicles, the „tester portfolio manager” will distribute test jobs between the „big iron” ICT and the Low Cost ICT based on criteria such as board complexity and production volume. This way, lower cost testers, fixtures and programs test boards that don’t require expensive capabilities like digital backdrive. Complex boards, such as those with specialized low-voltage chips are tested on machines with the required tester resources.
Tester Portfolio Management Saves Money
Tester Portfolio Management reduces total test cost by avoiding unnecessary tester overhead for test jobs that don’t require expensive „big iron” test capabilities–especially digital vector test (aka 'backdrive’). Because Low Cost ICT does away with the inherent complexity of digital test not only is the tester itself simpler and less expensive, but fixtures and programs, too. One user who implemented the same board on both types of testers experienced a greater than 75% cost savings in applications cost (fixture + test program) on the Low Cost ICT. Check out a similar case for yourself.
Consider Test Cost Up Front. Not After It’s Too Late.
When implementing new test jobs seek the lowest cost test solution by evaluating the total test cost ahead of time– even if it means investing in a „non-standard” Low Cost ICT . Today, „big iron” and Low Cost ICT coexist on an increasing number of test floors delivering much lower total testing cost than a single high-end „standard.” Even though building a tester portfolio instead of a single standard seems counterintuitive. That’s what a major automotive electronics manufacturer thought until they reduced test cost by more than 60% without any increased „escapes” to functional test.
Improve manufacturing margins by reducing test cost
Test is necessary but wasteful because it adds no value to the product. In today’s world of tight manufacturing margins circuit board test is an ideal cost reduction target. Yet, many OEMs and contract manufacturers (CMs) continue to generate unnecessary cost—and reduce their margins—by continuing to put every test job on their expensive ‘big iron’ in circuit testers with their high fixturing, programming and support costs.
CheckSum estimates that by sticking with traditional ‘big iron’ ICTs instead of investing in Low Cost ICT, OEMs and CMs unnecessarily spend more than $250 million per year in additional test cost. In a world where every margin dollar makes a difference, reducing that unnecessary cost is an ideal way to improve the manufacturing bottom line.
The example at right illustrates how a contract manufacturer with 5% gross margins can add 40 basis points to its gross margin—an 8% improvement—by reducing circuit board test costs by just 10%. One Tier 1 manufacturer found that it could reduce in circuit test cost by 60%. Even if ICT cost represents just half of total board test cost, that’s a 30% cost reduction.
CMs who have recognized and seized this cost reduction opportunity are enjoying both increased operating margins and competitive advantage. OEMs who recognize that test costs can be reduced are well positioned to negotiate lower overall prices from their CM.
3 steps to reduce board test cost
Myślenie poza jedną platformą w strategii testu.
Duże stałe testery obwodów sprzedawane są od lat jako platforma „robiąca wszystko”: analogowe w obwodzie; cyfrowy test wektorowy (backdrive), test wektorowy, programowanie ISP, skanowanie granic, test funkcjonalny oparty na oprzyrządowaniu itp.
Ujednolicenie wszystkich tych zadań może uprościć i ujednolicić zadanie grupy testowej, bez względu na to, jakie niespodziewane nowe technologie mogą wysłać projektanci produktu. Nie ma dodatkowego wyposażenia uzasadniającego zarządzanie i kupowanie. Personel jest już przeszkolony w zakresie korzystania z systemu. Wielki dostawca testerów stałych mówi: „Po prostu dodaj opcjonalny sprzęt i oprogramowanie, a będziesz gotowy”.
Ale rzeczywistość jest zawsze bardziej skomplikowana.
Strategia testu dwustopniowego
Na początku wydaje się to sprzeczne z intuicją, ale wdrożenie nowych testów na nowej, taniej platformie może drastycznie uprościć ogólne zadanie, przyspieszyć przepustowość i kosztować znacznie mniej niż próba zintegrowania wszystkiego w dużymstałym testerze. W jaki sposób?
New Circuit Board Technology Requires New Strategic Thinking
Circuit board technology evolves rapidly: more highly integrated devices, increasing package pin counts, denser placement of smaller components and thinner circuit traces. For boards ranging from simple to complex, the test and inspection process remains as critical as ever. Bad parts still find their way onto boards. Assembly and soldering defects still occur. In-circuit test (ICT) is still the most cost effective means to identify component faults and manufacturing process defects. And as long as there are circuit boards, ICT will continue to be the key to effective manufacturing process test.
But evolving technology requires a complete rethinking of in-circuit test strategy—and about the in-circuit tester itself.
Traditional ICT capabilities are increasingly expensive—and unnecessary
The Fault Spectrum Shifthas basically negated the cost effectiveness of traditional ICT testers such as the Agilent 3070-series and Teradyne TestStation. Capabilities found on these testers such as high-accuracy analog and digital vector test are increasingly superfluous because they are designed to test for faults that rarely—if ever—occur on today’s boards. In fact, traditional digital vector test is ineffective on today’s complex, highly integrated devices. And newer assembly defect classes such as cold solder joints and skewed components are simply invisible to in-circuit testers and must be diagnosed by other means such as automated imaging (AOI, AXI).
Evolving technologies aren’t the only reason you should reexamine your ICT strategy and equipment. Today’s smaller test departments and constrained budgets demand lower ICT costs. In a fixed budget environment every dollar you spend unnecessarily on ICT means a dollar that you can’t invest in new inspection technologies like AOI and AXI.
The Low Cost ICT strategy
Seeking a lower-cost ICT strategy demands that you examine not only the purchase price of the tester, but also ongoing operating and applications cost, such as fixturing, programming, and support. Keep in mind that no matter how low the purchase price, “big iron” ICT still has high overhead costs from complex test fixtures and lengthy test programming processes—even when built-in capabilities like vector testing are not even used.
The good news about new board and parts technologies and the resulting Fault Spectrum Shift is that much lower cost ICT systems will do the job as effectively as old, expensive ones. That’s where the CheckSum Analyst Low Cost In-Circuit Testers come in. Check them out and see how CheckSum can reduce testing cost and help increase manufacturing margins.
