Once the board has paste applied, the components are placed on top. This can be done by hand or by a machine. Using tweezers is a great way to place components. There is a common fallacy that you need large, expensive machines to make electronics. Not true! A human is quite fast at placing components and the surface tension of liquid metal is such that most components will shift into their correct location during reflow. But humans have a limit to their stamina. After a few hours it becomes harder to place components quickly. The small size of the components also tend to strain eyes.
You don’t need a pick and place machine to make electronics; you need a pick and place machine to build a lot of electronics.
SparkFun started by placing all the components by hand and we still do! But if we have more than about a hundred units to build we use a pick and place machine to allow us to build lots of boards.
A pick and place (PNP) machine is a robotic assembly device that uses a vacuum to lift a component off of a piece of tape, rotate it to the right orientation, then place it on a circuit board. It takes a few hours to setup a machine to build the assembly, but once everything is running, it is very fast.
In a large factory, a conveyor belt often carries the board directly from an automated paste deposition machine into the pick-and-place machines; at SparkFun, we move our boards manually around the production floor.
What is SMT Manufacturing?
Surface Mount Technology (SMT) is the method used to mount electrical components directly onto the surface of a PCB. This multi-step process begins with the stenciling solder paste. Think of it like screen-printing a t-shirt, only instead of ink, Qualitel uses a solder paste to print the paste, and then the pick and place machines place the parts on the board. After the PCB boards with components are mounted, they go through a reflow oven to melt the solder. The SMT process includes multiple inspection points to ensure the highest quality at every stage of manufacturing. Qualitel has five SMT lines, including two that are dedicated to their Express Prototyping facility for quick-turn electronics manufacturing and prototyping services.
SMD Spotlights vs. LED - What Is The Difference?
Since LED lights burst onto the market a few years ago, they’ve undergone some evolutionary changes that have improved varying aspects of their performance.
One of the most significant steps has been the emergence of SMD technology – short for Surface Mounted Device.
There are a number of reasons for its importance – and we’re going to look at some of those now.
Increase In Energy Efficiency
One of the biggest improvements is that SMD spotlights offer a higher lumen output for a lower energy consumption – making them more powerful and energy efficient than older LED lights.
This is because they work on the principle that fewer and larger SMD LEDs produce a greater lumen output. Let’s see how this works in practice then.
Our Dimmable 6W 27 SMD GU10 LED Bulb contains, as the name suggests, 27 SMDs. It shines with a maximum brightness of 450 lumens and uses 6W.
Now compare this to our 2.5W 48 SMD GU10 LED Bulb that has 48 SMDs. The brightness here is 268 lumens at 2.5W of power consumption.
As you can see, the bulb with fewer SMDs manages to achieve a much higher lumen count – the first bulb manages 16.67 lumens per SMD, whereas the second example only works out at 5.58 lumens per SMD despite having more SMDs.
It is worth remembering though that there is no industry standard for this rule and no two manufacturers follow the same principle.
Wider Beam Angle
SMD spotlights also take care of one of the early criticisms of LEDs from a few years ago – that their light was too concentrated and didn’t spread very well.
Typically, SMD bulbs have a beam angle of 120o – which even exceeds most halogen bulbs.
Indeed, if we go back to our 6W 27 SMD GU10 LED Bulb we looked at earlier, this too has a beam angle of 120o.
SMD LEDs also improve on what was an already impressive lifespan. Standard GU10 LED bulbs last up to 30,000 hours, but our SMD LEDs will keep going for up to 50,000 hours!
So let’s say you’re using your bulbs for an average of 8 hours per day. A 30,000 hour bulb will last you just over 10 years, but a 50,000 hour bulb goes way past that, and keeps shining for over 17 years!
Now think about if you’re using SMD LEDs across your whole house – this drastically reduces maintenance costs and ensures you spend a lot less on replacing your bulbs.
An added benefit of SMDs too are that they are surface mounted – arranged flat to the surface of the bulb. In comparison to our cluster GU10 LED bulbs, they use considerably less space.
Ultimately this means that our SMD spotlights are compatible with all halogen fixtures and are very stylish in appearance.
Taking all this into consideration, it’s probably worth thinking of SMD LEDs as a kind of ‘second generation’ LED light that have made the technology even more versatile and better placed to rival more traditional lighting solutions.
If you’re looking for lower essential energy costs with a high performance bulb then our SMD spotlights are definitely the bulb for you. Better yet, they’re available in GU10 and in MR16 format.
Types of SMT Stencils Based on Their Manufacturing
SMT stencils are made of robust materials and can be manufactured in different ways. The aperture can be formed on the stencil in any of the following ways:
Electroforming: The nickel is electroformed in this process to produce a stencil. It is also referred to as EFAB. There are high initial costs involved in the process. The process also requires high processing times than other manufacturing methods.
Laser Cutting: Apertures are created on a stencil foil using a laser machine. Laser cutting is a subtractive process, and it produces fine and accurate results, which is why it is favored over the other processes mentioned here.
Chemical Etching: As the name suggests, an aperture is created through chemical etching. The costs involved in the process are low; however, the results are much inferior to laser cutting process.
What Are the Different Types of Stencils Based on Solder Paste Application?
Stencils are divided into the following types based on solder paste application:
Prototype Stencils: These SMT stencils are designed for manual solder paste printing applications. Prototype stencils help eliminate printing mistakes. They are made from CAD files or Gerber files provided by the client.
Framed Stencils: These stencils are permanently fixed on the frame. They receive the necessary tension from border mesh. Framed stencils are used during bulk volume PCB production. Framed stencils feature smooth aperture walls, and they assure excellent print performance.
Frameless Stencils: Against framed stencils, these stencils are not permanently mounted to any frame. These stencils are comparatively affordable than framed stencils and are recommended for short runs or prototype runs.
How to create the perfect SMT reflow oven profile
Printed circuit board assemblies (PCBAs) are often viewed as commodity items. But consistently producing them in volume can take time to perfect.
Electronics manufacturing services (EMS) providers may well have their own preferences when it comes to their choice of machine type and brand. But, broadly speaking, the process steps that they go through to produce PCBAs are the same.
There is however one specific step that can make all of the difference when it comes to quality and consistency - creating the surface mount (SMT) reflow oven profile.
The reflow oven is used primarily for the reflow soldering of surface mount electronic components to printed circuit boards (PCB).
If you fail to profile the oven correctly, then all of the hard work and effort that has gone into loading feeders, programming the machines, optimising the build and then running the production line will be wasted.
So what should your EMS partner be doing to perfect their reflow oven profile? Let's find out.
Working on the baseline
The New Product Introduction (NPI) engineer will usually start the process by selecting an oven profile they have used before and that is stored on their system.
Over time, some EMS providers may develop a range of "baseline" profiles, which can then be selected depending on the PCBA they are working on. The time taken to perfect the baseline profile will pay dividends as most assemblies will then fall within one of them.
Baseline profiles may include:
One dedicated to densely populated assemblies with elevated temperatures
One dedicated to "standard" assemblies
One dedicated to assemblies that contain sensitive parts and require lower temperatures
Using their skill, judgement and experience, the NPI engineer will select the profile and temperature settings that they believe are best suited to the new assembly.