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How are LED strips made?

LED strip lights are currently one of the most popular light sources, especially among DIY projects’ enthusiasts, as they are low-profile, easy to set up, energy-efficient and extremely versatile. They’re commonly used for cabinet lighting, for displays or as ambient lighting mixed with other light sources. Let’s take a look at what exactly they are and how they are produced.

What are LED strips?

A LED strip light (a.k.a. LED tape) is in its essence a long and flexible circuit board with evenly spaced surface-mounted (SMD) LEDs and resistors. Each strip is equipped with a self-adhesive backing that can stick to almost all smoothish surfaces – as long as there are no big pores or lumps, they should hold in place. The diodes are placed sequentially, which allows the strip to be cut-to-length in designated spots (indicated by visible copper plates or even printed cut lines). This feature is very useful, as LED strip lights usually come in long reels (you can easily get ones that are 30 metres long!).

Despite their small size, the diodes can emit really bright light – some strips can go above 2200 lumens/metre, which is a rough equivalent of a 150 W incandescent bulb. Plus, they are very eco-friendly – there’s no mercury involved, and they transform about 95% of intake energy into light. Which makes them at least 80% more efficient than incandescent bulbs and less harmful than the CFLs (Compact Fluorescent Lights). The strips are low-voltage, so they need a dedicated LED driver/transformer to be safely connected to the building’s mains.

LED strip lighting comes in many colours – from standard warm white/cool white, through red, green, and blue (and any combination of these three), to colour-changing RGB LED chips that can be remotely controlled. Many LED lights can also be dimmable – make sure to check if yours are before trying to dim them.

If you want to buy LED strip lights, visit https://lucasled.ie/led-strip-lights – a source of various types of LED strips and accessories helpful in setting them up and controlling their work.

The production process of LED strip lights

Whether they are manufactured or made on automated production lines, the steps to produce fully functional LED strip lights are rather similar, although each company can have its own methods. It’s also worth mentioning that the process can be rather easily modified to suit various individual needs. Here’s how LED strips can be made:

Step 1 – Acquiring the components

To produce LED strip lights, you’ll need to gather all the required components, which are:

  • Printed Circuit Boards (PCBs)
  • SMD LEDs of various sizes, depending on the intended brightness
  • Wires and connectors
  • Thermally conductive adhesive tape

Quality Control 1: After the components arrive at the warehouse, they should be closely inspected and have their quality tested.

Step 2 – Drying the LEDs

The diodes often come straight from the manufacturer, so their phosphor is still wet. This means that they must be dried before they can be put on a light strip. To do that, they are placed for 12 hours in special ovens set to 70 °C.

Quality Control 2: After the diodes are nice and dry, it’s time to check their photometric data. For example, a spectrometer can be used to check their correlated colour temperatures (CCT) and colour rendering index (CRI). When their performance is on par with the manufacturer’s requirements, they are sorted (e.g., single colour ones are separated from the RGB ones), labelled and readied to placed on a flexible strip of PCB.

Step 3 – Creating solder moulds and applying solder paste on the PCB

To make sure each component ends up in the right place, aluminium cutout moulds (sometimes called LED waffles) are created for each strip and placed on the PCB base. Depending on the production method, the PCB is a long reel or made into a sheet of loosely attached strips (typically 50×50 cm).

Next, the solder paste is applied to the moulds’ holes, creating solder pads for the components.

Quality Control 3: At this point, the manufacturer makes sure that the paste was applied in the right places and in the right amount.

LEDs Sorted In A Factory
LEDs Sorted In A Factory

Step 4 – Placing the components

When the solder paste is applied correctly, it’s time to mount the LEDs and resistors on the soldering pads. This can be done manually or with a specialized pick-and-place (PnP) machine.

Quality control 4: Each strip/sheet is carefully inspected to make sure each component is correctly placed. Any defective batch is then reworked until it passes this quality test.

Step 5 – Reflow soldering

After the components end in the right places, the soldering paste must be hardened to keep them there. This is done by placing the PCBs in a special reflow oven, where they are gradually heated up to 250 °C and then gradually cooled down, which solidifies the paste. If the PCB was long, it gets cut into 50 cm strips before going into the oven. Fun fact – these ovens are similar to those used for cooking pizza and supposedly can also be used for that purpose.

Quality control 5: When the PCBs roll out of the reflow oven, the LEDs have their light output tested – all the diodes placed on a single strip should give off evenly intense light. Faulty strips are manually reworked (including soldering).

Step 6 – Soldering the strips

When all the components are stuck firmly to the PCBs, the sheets are separated into single 50 cm strips, which are then soldered together end-to-end to make LED strips of a specified length. This can be done manually or by a robotic welding arm. After this process, the PCBs can finally be acknowledged as LED strip lights… although they still need some work before they can be shipped out.

Quality control 6: When the strips reach bespoke lengths, each of them is thoroughly examined optically – any loose connections or components have to be redone. At this stage, the strips’ illumination and heat-dissipation is also tested.

LED Strips Are Easy To Solder Together
LED Strips Are Easy To Solder Together

Step 7 – Soldering wires and ageing

Most of the LED strip lights receive pre-soldered wire leads that makes them easier to connect to a transformer. These wires are then put into heat shrink tubes to secure the connection.

Almost ready LED tape lights are then subjected to the so-called ageing process – after being moved to a special room, they are hung and turned on for a solid 8-12-hour period. If the strips came out from a new design, they are also placed in a separate oven and tested for humidity and temperature tolerance.

Quality control 7: Aged strips are subjected to yet another QA test.

Step 8 – Waterproofing and applying tape

The LED strip lights are almost ready – all that’s left is applying waterproofing and the sticky tape. Waterproofing is done using a thin layer of silicone/plastic (or both). This process is optional, but ups the longevity of the strips. And lastly – adding 3M paste to their backs. As already mentioned, this enables easy installation.

Quality control 8: When the LED strip lights are ready, it’s time for the final QA – after making sure the waterproofing and tape are applied correctly, random strips are subjected to efficiency tests. All that’s left after that is to wound them up on a reel and package them for shipping.

What determines a LED strip light’s quality?

There are three main factors that affect the overall quality of LED lights:

  • PCB’s copper wiring – the wires that transport electricity throughout the PCB greatly impact its longevity. When picking up LED strips, make sure they use 3-4 oz wires for best effects.
  • Diodes’ phosphor quality – the higher it is, the brighter and more long-lasting the diodes are.
  • Components’ quality – good quality components will make the strip perform better and last way longer without faults.

LED strip lights are one of the most versatile light sources. They’re great for both indoor and outdoor projects. To make sure you pick up the best ones, always buy them from a trusted source.

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