# Ceramic PCB Copper Peel Strength: Can You Compare Two Reports? _Published: 2026-11-14_ Table of Contents Toggle - Copper Peel Strength: What the Number Means - Peel Strength Test Method: Match These Inputs - 90 vs. 180 Degree Peel Test: Compare the Geometry - Peel Strength Calculation: Normalize Before Comparing - Peel Test Failure Modes: Inspect the Separated Surfaces - DBC vs. AMB: Read the Datasheet Conditions - Thermal Cycling Test: Keep Conditioned Results Separate - Peel Strength Test Report: Decide Whether to Release - Frequently Asked Questions - References - Discuss Your Ceramic Substrate Acceptance Plan Do not approve a ceramic PCB lot from a peel-strength number alone. First match the specimen construction, peel angle, speed, conditioning and reporting interval. Then check where the specimen failed. A copper strip that tears and a strip that separates cleanly at the ceramic interface do not establish the same result. Suppose two suppliers submit reports for a power-module substrate. One lists 18 N for a 4 mm strip; the other lists 20 N for a 5 mm strip. The second asks you to approve its lot because its force is higher. Before deciding, normalize the force and check whether the tests were equivalent. All example numbers below are hypothetical. ![Copper strip above a flat ceramic coupon in a laboratory fixture](https://www.bestpcbs.com/blog/wp-content/uploads/2026/11/ceramic-copper-peel-report-cover.jpg)Illustrative test setup. Verify which angle the fixture maintains during the evaluated travel. ## Copper Peel Strength: What the Number Means Peel strength is force per unit width under a defined peeling procedure, commonly reported in N/mm. The instrument pulls a prepared strip while the fixture controls its orientation. The recorded force can include bending or deformation of the copper as well as separation from the underlying structure. It is not a material constant or an allowable design load. Define what the purchase drawing requires. A minimum sustained peel result at a named condition is not interchangeable with the maximum force reached while starting the strip. Ask for the trace or calculation interval when the report gives only one rounded result. ## Peel Strength Test Method: Match These Inputs Before comparing reports, make sure they describe equivalent specimens and the same test. The manufacturing route, ceramic grade and copper thickness all matter when the result is used for incoming acceptance. **Report field** **What you need to check** Substrate and copper construction Exact grade, bonding route, copper thickness and tested face Peel geometry and speed Actual angle, fixture arrangement and specified test speed Specimen geometry Measured strip width, preparation and position on the coupon Condition and reported result Temperature or conditioning, measured interval, statistic and failure location ## 90 vs. 180 Degree Peel Test: Compare the Geometry At 90 degrees the peeled strip is drawn approximately perpendicular to the substrate face. At 180 degrees it is folded back along the plane in the opposite direction. The geometries load and bend the strip differently. Use the configuration named by the purchase specification or approved test plan; do not convert one result into the other with a fixed multiplier. **Method** **When to select it** **What to verify** 90-degree peel The production acceptance plan calls for perpendicular peeling. The fixture maintains angle through the evaluated travel. 180-degree peel The approved procedure calls for back-fold peeling and the strip can be prepared accordingly. The strip does not fail prematurely during preparation or bending. If neither method can produce a representative strip, ask for an approved alternative assessment and define a separate acceptance criterion. Do not reuse a peel limit for a different loading mode. ## Peel Strength Calculation: Normalize Before Comparing Divide the specified force statistic by the actual strip width. If the two hypothetical reports use the mean over the agreed interval, 18 N divided by 4 mm gives 4.5 N/mm, while 20 N divided by 5 mm gives 4.0 N/mm. The apparent ranking reverses after normalization. That arithmetic still does not resolve the purchasing decision. If one report used a peak and the other used an average, or their peel angles differ, ask for a matched test. A normalized unit makes the comparison possible only after the method and specimen have been matched. ## Peel Test Failure Modes: Inspect the Separated Surfaces Record whether separation followed the bond, whether ceramic fractured or whether the copper strip tore. Retain photos of both sides with the specimen identifier and correlate the event with the force trace. A change in the trace is a reason to inspect; it does not identify the failure plane by itself. If the strip tears before the specified interval is complete, do not enter its tear load as a normal bond-strength result. Apply the method’s invalid-test or alternative-reporting rule. If the procedure leaves the treatment unclear, retain the data and agree on a retest before release. ![Separated ceramic coupon pieces and copper on an inspection bench](https://www.bestpcbs.com/blog/wp-content/uploads/2026/11/ceramic-copper-peel-report-detail.jpg)Illustrative specimens. In an actual report, retain images of both fracture faces and the specimen identifier. ## DBC vs. AMB: Read the Datasheet Conditions Rogers curamik technical data sheet 135-004, version 1.19 JP, page 2, lists at least 4.0 N/mm at 50 mm/min for its DBC construction with 0.3 mm copper and at least 10.0 N/mm at the same speed for its AMB construction with 0.5 mm copper. These are supplier-stated results for different constructions, not a controlled experiment isolating the bonding process or universal acceptance limits. See the [curamik data sheet, “Copper peeling strength”](https://www.rogerscorp.jp/downloads/JP-Technical-Data-Sheet-curamik-Ceramic-Substrates.pdf). For the power module, compare offers against the same assembly requirements rather than ranking bonding routes by their datasheet numbers. Request evidence for the exact build you would buy. ## Thermal Cycling Test: Keep Conditioned Results Separate An as-received peel result can support an incoming check. It does not establish adhesion after repeated temperature changes or prove the reliability of the assembled module. If conditioning is required, document the profile, number of cycles, specimen state, and acceptance method before the test. Use matched specimens for the baseline and conditioned checks. Peel testing damages the specimen, so do not describe a before-and-after comparison as repeated measurements on the same already-peeled strip. If the failure location changes after conditioning, report that as well as the force. ## Peel Strength Test Report: Decide Whether to Release First verify that the report applies to the received lot and agreed construction. Then verify the method and calculate the specified result. Release only when the required measurements and failure reporting meet the approved criteria. If the suppliers used different methods, request a matched retest rather than applying an unverified conversion. The [Best Technology DBC yellowing test report](https://www.bestpcbs.com/images/ceramic-pcb/Test-report-of-ceramic-yellowing-BestTechnology.pdf) is an example of reporting individual peel-force statistics and normalized strength. Its conclusion applies to the specimens in that report, not every discolored ceramic substrate. ## Frequently Asked Questions ### Is 4 N/mm a universal DBC minimum? No. Use the limit and test procedure agreed for the actual construction. ### Does a higher peak mean a stronger interface? Not necessarily. The peak may reflect initiation or deformation. Compare the same defined interval and statistic. ### Can 90-degree and 180-degree results be averaged? No. They are different configurations. Report them separately unless a qualified procedure establishes equivalence for the specific application. ### Why record copper thickness if the result is already in N/mm? Dividing by width does not remove thickness-dependent bending or deformation. ### What if I cannot peel the thin copper without breaking it? Document that outcome and agree on a more suitable test and its acceptance criterion. Do not treat the tear load as a direct adhesion result. ### Does a good peel result prove a ceramic card will pass insulation testing? No. Use the agreed electrical test for the insulation requirement. ### Can I apply an as-received report after thermal cycling? No. Request the relevant conditioned evidence if it is required by the qualification plan. ### What evidence helps resolve a supplier disagreement? Send the approved drawing, lot identity, raw force traces, specimen dimensions, fixture details and photos of the failure surfaces. ## References [EP4310065A1: ceramic composite substrate, example of perpendicular peel geometry](https://patents.google.com/patent/EP4310065A1/en). This is a documented test example, not a universally applicable acceptance standard. ## Discuss Your Ceramic Substrate Acceptance Plan Send the ceramic grade, copper construction, drawing and proposed test method to [sales@bestpcbs.com](mailto:sales@bestpcbs.com) for a Best Technology review. Identify whether the decision concerns a new material qualification or the release of a received lot.