Evaluate ITEQ CAF resistance through the evidence for the exact laminate construction and fabricated board, rather than ranking materials by a generic 鈥淐AF resistant鈥� label. A useful selection record connects material identity, conductor geometry, fabrication process, environmental exposure and an agreed test method.
Conductive anodic filament formation is an internal electrochemical reliability concern in glass-reinforced laminate. This guide helps designers and buyers review ITEQ material evidence and prepare a meaningful qualification request. It does not provide a universal safe via pitch, predict service life or certify a finished board from a laminate datasheet.
1. Separate the material claim from the board-level requirement
CAF is associated with conductive growth through internal laminate paths, often along the glass-resin interface, under moisture and electrical bias. Conductor arrangement, processing damage and the material construction influence the opportunity for such a path. A finished board can pass a functional check and still require a separate environmental reliability assessment. Conversely, an intermittent leakage result is not by itself proof that CAF caused the failure.
Keep internal CAF separate from surface electrochemical migration and from surface tracking. They may share environmental influences, but a surface cleanliness measurement or a comparative tracking index does not establish internal CAF performance. A failure investigation must locate the conduction path and consider alternative causes before attaching a mechanism label to a resistance drop.
ITEQ鈥檚 official identifies CAF resistance as a feature of IT-180A. Its linked , also describes that feature. The one-page sheet does not supply the coupon geometry, applied bias, duration and population results needed to qualify your particular design.
Use that distinction when evaluating other ITEQ grades. If a supplier proposes IT-988GSE, IT-998G or another grade, request its current exact-grade documentation and applicable CAF report. Do not assume that a lower dissipation factor, lower moisture-absorption number or higher Tg establishes a better CAF ranking. Electrical loss, thermal behavior and electrochemical reliability answer different questions and may be measured under different conditions.
Define the requirement at the conductor pair
Identify the most relevant locations in the actual design: adjacent plated holes, a plated hole near an internal plane edge, or other biased copper features separated by laminate. Record the potential difference, geometry, dielectric construction and expected exposure. Treat condensation, contamination and product enclosure behavior explicitly where they matter. 鈥淚ndustrial use鈥� or 鈥渁utomotive use鈥� alone does not define a test condition.
For a material-selection discussion, bring the proposed stackup and fabrication constraints as well as the application description. The ITEQ PCB manufacturing page is the appropriate next step for discussing a specific material build. Catalog availability and a material feature statement remain separate from confirmed sourcing, process capability and qualification of the ordered construction.
2. Read a CAF report as a complete test configuration
provides a method for assessing CAF and other internal electrochemical migration tendencies in printed boards. Record the method and revision used, together with the laboratory鈥檚 actual procedure and agreed acceptance. Referencing the method number alone does not communicate every project-specific condition or establish that two supplier results are comparable.
Ask for the test-vehicle drawing and material build. It should identify the laminate/prepreg combination, thicknesses, glass style or other relevant construction detail, conductor patterns and hole definitions. The report should make clear which separation is measured: center-to-center pitch, nominal hole-wall distance and actual copper-to-copper separation are not interchangeable descriptions.
Next review conditioning and processing. Record the fabrication route represented by the specimens, any thermal preconditioning or assembly simulation, moisture exposure and time between steps. A report on a different drilled construction or thermal history may still be useful evidence, but its applicability must be evaluated rather than silently assumed.
Review environmental conditions, applied bias, resistance measurement conditions and observation intervals as separate entries. A familiar label such as 鈥�85/85鈥� gives only temperature and relative humidity, not a complete CAF test. A stated duration alone also cannot tell you the conductor spacing, voltage stress, failure criterion or the number of specimens tested.
| Report field | What to request | Why it changes interpretation |
|---|---|---|
| Material and construction | Exact grade, reinforcement and layer construction | A family name does not identify the tested build |
| Coupon geometry | Drawing, conductor pair, orientation and spacing definition | Nominal pitch can hide a different insulation path |
| Process history | Drilling, lamination and thermal preconditioning | The tested process may differ from the order |
| Stress and measurement | Temperature, RH, bias, duration and measurement method | A pass is conditional on the test configuration |
| Population and outcome | Specimens, tested pairs, failures and resistance histories | A single pass label hides sample size and variation |
Make the failure rule explicit before reviewing the result. Ask how transient drops, interruptions, contaminated fixtures and instrument limits are treated. Preserve individual resistance histories and the denominator for every reported pass fraction. If a report says all specimens passed, ask how many independent boards and conductor pairs were tested; those are different population descriptions.
Keep accelerated screening and service-life prediction separate. A result after a specified number of hours under one stress does not automatically translate into a number of years in the field. That translation requires an applicable model and evidence for the relevant mechanism. Avoid using a marketing comparison table to make an unsupported lifetime commitment.
3. Review geometry and fabrication before choosing a grade
Start with geometry rather than a universal material-by-pitch table. Two designs with the same via pitch may have different drilled-hole sizes, copper shapes, layer constructions and potential differences. Compare the actual closest relevant conductors, not only the grid used for component placement. Ask the fabricator how drilling and registration tolerances affect the constructed separation.
Worked geometry example
For two equal circular holes, an idealized nominal edge separation is g = p 鈭� d, where p is center spacing and d is the diameter used for the geometric model. With illustrative p = 0.65 mm and d = 0.30 mm, g = 0.35 mm. If the minimum center spacing were 0.60 mm and the maximum modeled diameter 0.35 mm, the corresponding geometric gap would be 0.25 mm.
This calculation is bookkeeping for a review, not a CAF threshold. It ignores local damage, actual barrel shape, copper registration, resin/glass interfaces and other possible paths. State whether the diameter is a drill, finished-hole or measured conductive-boundary dimension; choose the correct construction data with the fabricator. A simple subtraction cannot determine whether the board is qualified.
Discuss drilling, desmear, plating and lamination controls for the chosen resin system and stackup. Request evidence relevant to those operations instead of prescribing one drill speed or chemistry for every laminate. Process changes can alter the represented construction, so agree which changes require notification, engineering review or renewed qualification. A material substitution is not acceptable merely because the supplier considers it a comparable loss class.
Keep thermal reliability checks in the selection record, but do not use Tg as a complete proxy for resistance to assembly stress. Document the actual intended assembly and rework history and the evidence supporting it. A high-Tg label does not remove the need to review the finished board鈥檚 construction and processing.
Conformal coating and enclosure design may contribute to an environmental protection strategy, but neither automatically qualifies the laminate against internal CAF. Review coverage, interfaces, moisture exposure and validation separately. Similarly, a 鈥渘o-clean鈥� flux designation does not mean residues are acceptable under every service condition. Surface contamination testing and internal CAF assessment should each answer their own defined questions.
Record both the design margin and what remains unproven. If the proposed construction has tighter spacing or different processing than the available coupon report, mark that mismatch. Possible next actions include changing the geometry, obtaining a representative test vehicle or reviewing another construction. Do not assign a numerical risk score without a validated basis.
4. Turn the evidence into a purchasing and qualification record
Prepare a one-page request that names the proposed ITEQ grade, stackup revision, relevant conductor pairs, operating exposure and required evidence. Separate 鈥渕andatory鈥� requirements from preferences and unknowns. If the construction is not yet selected, request an engineering recommendation and supporting evidence instead of issuing a drawing that appears final but leaves the critical choice open.
For comparison, place candidate reports side by side and first mark differences in method revision, coupon, spacing, thermal history, bias, duration and sample population. Only after that should the team compare outcomes. A longer test on an easier geometry cannot automatically outrank a shorter test on a more demanding one. An unreported value is unknown, not zero and not a failure.
Agree who accepts the evidence and when procurement can proceed. Material supply, fabrication release and product qualification may have different owners. Keep approved alternatives under change control, including any construction restrictions. When repeat orders are placed, retain the exact approved configuration and the notification requirements for a material or process change.
For a failed or suspicious test, preserve specimens and measurement records. Review fixture leakage, contamination, handling, measurement setup and competing failure mechanisms before concluding that a particular grade is unsuitable. A qualified failure-analysis plan may require localized inspection or sectioning; indiscriminate rework or cleaning can remove evidence. Record the investigation鈥檚 limits and distinguish confirmed mechanism from hypothesis.
The useful outcome is a traceable decision: which evidence was accepted, for which construction and conditions, with which unresolved risks. Store the report revision, supplier response, test-vehicle drawing and approval together. This makes a future engineering change review more efficient than relying on a remembered 鈥減ass鈥� from a previous project.
Questions to resolve before the next order
Is low moisture absorption enough? No. It is one material characteristic; it does not establish the result of a particular CAF test or account for board geometry and process history. Is a coating sufficient? It must be evaluated as part of the product鈥檚 protection system and does not replace internal laminate evidence. Can a supplier鈥檚 pass be reused? Review applicability to the actual construction and acceptance requirements rather than assuming all boards made with the grade are equivalent.
For the fabrication discussion, use PCB manufacturing review to define the proposed stackup, process route and requested records. Send the existing evidence and the unresolved conditions through Contact. This page provides a review framework; it does not claim that 吃瓜tv has performed a specific CAF qualification or guarantees an untested service life.