吃瓜tv 路 Copper specification desk
1 oz copper PCB: turn a nominal weight into a usable specification
1 oz copper is approximately 35 碌m, or 0.035 mm. Check finished thickness, trace voltage drop and the evidence needed for a repeatable PCB order.
Preliminary copper specifications and open manufacturing questions are welcome.
How thick is 1 oz copper in millimeters?
One ounce of copper per square foot corresponds to approximately 35 碌m, or 0.035 mm, commonly rounded to about 1.38 mil. Some engineering references use 34.8 碌m for the conversion. Both are useful nominal conventions; neither automatically defines the minimum finished copper on a delivered PCB. The board itself may be much thicker because its construction includes dielectric layers and other materials.
A 1 oz copper PCB is a useful starting specification for many signal and moderate-power circuits, but the label does not establish current capacity, impedance or thermal performance. It also does not say whether every layer has the same copper. A four-layer board may use different starting foils and finished copper requirements on inner and outer layers.
This page helps turn a common purchasing label into an electrical and manufacturing definition. If the immediate decision is whether to increase copper, use the 2 oz comparison and design page after checking the present geometry. A wider or shorter path may solve a problem without changing every layer.
Specify finished copper before comparing orders
Start with a layer schedule. Identify the signal, plane or power role of each layer, then separate the base material description from finished copper acceptance. A statement such as 鈥淟1 and L4: minimum finished copper to drawing requirement鈥� has a different purpose from 鈥渙uter starting foil: half-ounce.鈥� Record both when the manufacturing route needs both.
The concerns supplied metal foil. The concern rigid-board qualification and performance, including conductor definition and plated structures. Their public previews establish those roles; they do not justify copying an unverified acceptance number into every drawing. Use the contractually selected revision and requirements for the actual product.
| Item | Put in the release | Avoid this ambiguity |
|---|---|---|
| Layer copper | Base or finished, nominal or minimum, layer number | 鈥�1 oz everywhere鈥� without a construction |
| Trace geometry | Finished dimensions and measurement convention | Using CAD width as measured copper area |
| Hole copper | Plating requirement and inspection scope | Assuming surface thickness equals barrel thickness |
| Board thickness | Complete stack and coating convention | Confusing 35 碌m copper with total PCB thickness |
| Finish | Type and application requirements | Adding finish thickness to the bulk-copper model |
If an outer process begins with thinner foil and adds copper, the starting weight can differ from the finished conductor label. The half-ounce foil guide provides an interval worksheet for that discussion. The accepted fabrication record should resolve the process rather than leave a buyer to infer it from the quotation.
Estimate trace resistance, voltage drop and DC loss
The worksheet uses your finished trace length, width, copper thickness and conductor temperature. Current then gives voltage drop and Joule loss. Enter a voltage-drop budget for this specific trace if you want to see the remaining electrical margin. Passing that budget does not establish a safe temperature or a maximum current rating.
1 oz Copper DC Voltage Drop
The model is R = 蟻L/(wt), with an approximate copper resistivity of 17 脳 10鈦烩伓 惟路mm at 25掳C and a temperature coefficient of 0.0039/掳C. It multiplies room-temperature resistance by 1 + 0.0039(T 鈭� 25). Length, width and thickness are all converted to millimeters internally. These are planning assumptions consistent with the calculation approach in (the guide uses 16.8 脳 10鈦烩伖 惟路m; this worksheet rounds resistivity to 17 脳 10鈦烩伖 惟路m); measured geometry and material can differ.
Consider a 100 mm long, 2 mm wide trace with 35 碌m finished copper at an entered conductor temperature of 75掳C. The calculation gives about 29.02 m惟. At 2 A, that trace drops about 58.04 mV and dissipates 0.116 W. If its allocated drop is 50 mV, the model reports a negative margin of about 8.04 mV. It does not conceal the shortfall by displaying a general 鈥減ass.鈥�
Temperature is an input, not an output. Entering an ambient temperature while ignoring self-heating can understate operating resistance. For a conservative electrical screen, use a defensible conductor-temperature condition and the agreed minimum finished geometry. Thermal assessment and physical testing determine whether that temperature condition is credible.
Include the return path and the interfaces
A load sees the complete circuit. If outgoing and return traces have the same resistance, their contribution to loop drop is twice that of either trace alone. Connector contacts, plated holes, shunts, protection devices and soldered interfaces add further resistance. A generous power polygon does not remove a narrow connector escape or a poor joint from the series path.
Allocate the supply tolerance across the system rather than giving the entire voltage budget to one PCB trace. For a low-voltage sensor or processor rail, tens of millivolts can matter even when the trace is thermally comfortable. Remote sensing changes where regulation is measured, but it does not eliminate conductor heating or all load-transient behavior.
The simple rectangular model is most useful for a uniform DC route. It excludes current spreading through irregular pours, thermal reliefs, skin and proximity effects, and temperature gradients. Use more detailed analysis for those conditions. For a switching power stage, preserve a compact return loop and review the component manufacturer's layout guidance; extra copper thickness does not repair an inductive loop.
What should change when a 1 oz design is marginal?
First identify the limit. Excessive steady-state voltage drop suggests reviewing path length, width and finished thickness. A hot connector may require a terminal or joint change. An impedance mismatch needs an electromagnetic geometry review. Board temperature also depends on component dissipation, copper planes, mounting and airflow. These are related tasks with different evidence.
For controlled lines, changing copper thickness can change the required width and spacing. Keep the intended finished geometry with the PCB impedance requirements. For multilayer boards, coordinate that request with the multilayer stackup so that a copper change does not silently alter dielectric spacing or the approved board thickness.
For a power route, compare a width increase with a copper increase at the same conductor temperature. If the local geometry is the bottleneck, a global copper change may create extra process cost while leaving the critical restriction. Include the pad entrance, thermal relief and return conductor in the design review before choosing the next copper class.
This separate 2 oz product is a comparison example, not proof that it is interchangeable with a 1 oz layout. The transfer depends on geometry, manufacturing process and the electrical requirement. Use the actual file revision to request alternate constructions; do not compare unrelated catalog boards as if they were a controlled experiment.
Agree where copper is measured
Surface conductor thickness, hole-wall copper and the solderable finish need different callouts. Even a valid measurement at one location does not automatically represent the minimum everywhere on a panel. Agree on coupons or board locations, sampling and the required report. Retain the measurement conditions with the production lot so a later discrepancy can be investigated.
For incoming inspection, check that the report applies to the delivered revision and construction. A photograph can support identification, but it cannot replace a dimensional or electrical measurement. A certificate describing the supplied laminate also does not establish the final conductor after processing. Request only the evidence that serves the product requirement, and have its scope included in the quotation.
Electrical continuity testing is valuable for opens and shorts, but an ordinary pass is not a full verification of voltage drop under load. If a resistance limit matters, define the measurement method, temperature, contacts and acceptance threshold. Use a repeatable arrangement so differences between lots are not confused with fixture resistance.
Keep a 1 oz quotation comparable
Quote against the same layer schedule, laminate, board outline, finish, hole requirements and inspection plan. Copper weight is one input; layer count, imaging complexity, panel utilization and process steps also affect the total. Avoid presenting a fixed percentage premium for another copper weight without a matching supplier quotation.
Open optional hardware budget and RFQ brief
1 oz PCB Budget and RFQ Brief
The budget brief totals entered bare-board, setup and verification allowances using the shared pricing arithmetic. It contains no current market rates. All costs may remain blank when you only need an engineering enquiry. If you change the geometry, layer count, quantity or scope, re-enter costs against that revised definition. This prevents an old price assumption from appearing valid for a new construction.
Practical 1 oz copper questions
Is 1 oz always 35 碌m after manufacture?
No. Thirty-five micrometers is a rounded nominal conversion. Starting foil tolerance, copper addition and process loss can influence the finished value. Specify the minimum required finished conductor and its verification basis rather than treating the label as an exact measured thickness.
Can I obtain a current rating from trace width alone?
No. Width and copper thickness establish part of the conductor geometry, but allowable temperature, surrounding copper and heat transfer also matter. provides a conductor-sizing framework. The DC worksheet on this page deliberately reports electrical loss without converting it into an unsupported current limit.
Is 1 oz unsuitable for power electronics?
Not inherently. The appropriate construction depends on current paths, allowable loss, component heat and available area. Some designs can use wider or shorter routes; others need heavier copper, additional conductive paths or a different architecture. Evaluate the actual limiting requirement before choosing a copper class.
What makes a useful first enquiry?
Send the layer schedule, fabrication files, quantity, finished-copper requirement and the main electrical or manufacturing concern. If you only have a partial design, include the critical path and expected operating condition. You can request engineering feedback directly without using the worksheet or supplying a guessed price.
Request a 1 oz Copper PCB review
Send the board revision, copper by layer, base or finished requirement, outline, quantity and test scope. Include the bottleneck or unresolved manufacturing question so the quote can address it.
Tool use is optional. Attach any downloaded brief manually; Contact does not automatically receive worksheet inputs. References reviewed September 2026. Illustrations are explanatory, and photographs are not process qualification records.