Connect COB LED strips after cutting: pads, solder and service loops

CHECKPOINT / 01

Read the COB circuit as a set of cuttable sections

A COB strip can appear like one continuous phosphor line, but its PCB still contains repeated electrical sections. The cut interval, voltage and grouping must be taken from the exact variant. A clean-looking line is not evidence that the board can be cut anywhere. Mark the section boundary and preserve enough copper for the connector or soldered lead.

• Confirm the cut marks under good light before trimming.
• Keep the strip straight while cutting so the PCB is not twisted.
• Do not infer free-cut behavior from a different COB family.

CHECKPOINT / 02

Match the COB connector to the board

Solderless COB connectors are useful when the strip width, pad spacing and contact design match. Insert the strip far enough for every metal contact to land on its corresponding pad, then close the cover evenly. For CCT, RGB, RGBW or addressable COB variants, pin count and signal meaning change. A two-pin single-color connector is not a universal COB accessory.

• Confirm width with the coating removed where the connector requires it.
• Match positive, negative, channel and data pads exactly.
• Check that the connector height clears the diffuser and channel cover.

CHECKPOINT / 03

Use a controlled solder joint when the project needs it

Soldering can provide a compact and serviceable connection when the installer can control heat, ventilation and strain relief. Tin the wire and the clean pad lightly, heat the joint only long enough to flow the solder, then let it cool before moving the strip. Do not solder against a metal heat sink or press the hot iron into the COB surface. Inspect for bridges and give the cable a mechanical support point.

• Disconnect the supply and keep the iron tip away from the silicone and diffuser.
• Use a wire gauge that fits the branch current and pad size.
• Pull-test the cooled joint gently before adding its end treatment.

CHECKPOINT / 04

Plan power and corners as physical assemblies

A COB strip still consumes current along its path, and a long run can require separate feeds or injection. Keep power branches parallel where the calculated current and voltage drop require them. At a corner, use a bend radius, cut-and-join method or corner connector that the strip supports; forcing a sharp fold can damage the PCB and break the continuous optical line. A silicone cover or aluminum profile can protect and diffuse the result, but neither substitutes for a sound joint.

• Calculate the load from the exact COB watts per metre.
• Leave a service loop before the strip enters a hidden corner.
• Use a profile or cover that fits the joined height and width.

CHECKPOINT / 05

Test the joint before sealing or mounting

Power a short section first, then test the complete branch at low, normal and maximum planned brightness. Check for a dark section, reverse polarity, a channel mismatch, flicker, far-end drop and heat at the joint. Once the electrical behavior is correct, complete the seal or cover and test again. Keep the connector or solder method in the BOM so a future replacement preserves the same pad and voltage map.

• Inspect the phosphor line for a break or visible dark spot.
• Measure loaded voltage at the start and end of the branch.
• Do not close an inaccessible joint until the final seal has been reviewed.

FAILURE MODES

What usually goes wrong

• The seamless appearance is mistaken for an unrestricted cut interval.
• A connector fits the width but its contacts miss the COB pads.
• The soldering iron overheats the PCB or the joint is left without strain relief.
• A sharp 90-degree fold damages the strip at a corner.
• The strip is sealed before the joint, branch current and far-end brightness are tested.

TECHNICAL BASIS / VERSION

Keep the decision current

This guide is maintained as a versioned technical record. Recheck the current protocol documentation and the exact product revision before using it in a production installation.