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DIY Surface Mount Soldering and PCB Assembly

This page is to demonstrate how easy it is to solder very small electronic SMD (surface mount device) components on your PCB board. It is easier to work with compared to through-hole components. The component insertion time is shorter, and there are no component’s leads to cut away after the soldering. This save time and cost.

SMT (surface mount technology) methods of assembly PCB has significantly improve the production efficiency. Not only it reduces the board size and board cost, SMD components are usually costing lesser. The SMT design also make automation of PCB assembly much more efficient.

The re-work with SMT boards is also simpler. Using a hot air blower, it is very simple to de-solder and re-solder of a 44 to 100 pins IC chip.

There are many methods to working with SMT components. The following presents some of the cost effective methods suitable for low volume production.

Advantages of Working with SMT Board

  • Smaller
  • Faster
  • Cheaper
  • Lower probability of being obsolete

The board size can be smaller reducing your product size and weight. The use of lesser material can help minimise cost.

As more production is using SMT, the cost of the surface mount components will usually be cheaper than the through-hole version. The chances of the component’s package being forced end-of-life or obsolete is also lower compared to through-hole.

Due to the simple assembly of surface mount, it simplifies the assembly automation for mass production. This not only speed up the assembly process, ultimately the cost of assembly is going to be lower.

The small component and devices will also use up less space for your logistic storage. It takes less space to keep your component parts and your finished product. The reduce weight and size also helps to lower your shipment cost.

Disadvantage of Working with Small Components

  • Not suitable to deploy in a very dirty and dusty environment without an enclosure.
  • May be too small to work with for some technician.
  • Additional tools and equipment may be required

SMT is not suitable to deploy in a very dusty and dirty environment with proper enclosure protection. There is a conductivity in every material. A dust may fall in between the fine pitch of the IC chip and unintentionally causes a connection or short circuit. This may result in a faulty circuit operation. It is important to keep the circuit free from dust and dirt especially when the pitch distance between the pins are 1mm and smaller.

Some technical may find it harder to work with SMT components. A better eye sight compared to working with through-hole compoents. Their hand should not be shakey when placing very fine pitch components.

While SMT soldering can be done by an ordinary soldering iron, some tools are recommended to better help you work with SMT.

  • A pair of good staineless steel tweeter.
  • Flux to clean the contact surface.
  • Hot Air Rework Station for doing rework.
  • Reflow Oven for small volume mass production.

The following are some useful videos that was posted in You-Tube. Check them out to see for yourself how easy is it to work with SMT components and boards.

Manual Iron Soldering of a Passive Component

SMT components may be small but you can still solder with a soldering iron with ease. This is a video of how a SMD resistor (size 1206) is manual soldered using a solder iron. You can easy solder resistor, capacitor, inductor and diode using this method.

Smaller component size like 0805 is still relatively easy to work with using a simple tweeter and a iron. Size 0603 component can still be managable. Component size 0402 and below will be much tougher. It may be too small for your tweeter to hold. It is still possible but much challenging to work with.

The size which is comfortable for a technician to work with is subjective. As a general rule, the minimum size of 0805 should be easy enough to work with for most age group. For technical that is age 40 and above, they may find it challenging to work with component size 0603, 0402 and below.

Manual Iron Soldering of Fine Pitch IC Chip

This method of soldering small SMT IC chip is applicable to IC pin pitch as low as 0.6mm distance apart.

The key ingredient is the use of flux to keep the solder flowing like a liquid so that it will not bridge as a lump. Flux may not be neccessary for passion components or IC chip with pitches of 1.27mm and above. It is a must for SMT IC components with fine pitches.

A clean iron tip will improve the soldering experience. Always tin your soldering iron tip when it is not in use. Tinning acts as a layer to prevent the soldering tip from oxidising. An oxidised tip will act as an insulator prevent the heat from flowing to the component’s lead. Tin the tip when you are not using the iron for the next 5-10 minutes. Tinning is recommended if the iron heating is left idling for some time or before it is powered off.

De-soldering and Re-soldering of Fine Pitch IC Chip

SMT IC chips may seems small to work with. Actually the rework is much simpler when you have a Rework Station equipment. This equipment blows out hot air which will melt the solder on the board. This allows you to remove the SMT component easily with a tweeter. The same equipment can also help you to solder SMD component with ease.

Reflow Soldering Method for SMT PCB Assembly Production

Reflow method is a simple method which allows you to solder your boards at one go using a reflow oven. The following steps provides you an overview of the PCB assembly process.

  1. Apply soldering paste to the bare PCB board using a stencil.
  2. Place your SMT components on the PCB board that was applied with the paste.
  3. Place the assembled PCB board into the soldering oven for a couple of mintues.
  4. Yes. Your boards are now soldered. It is so simple.

The following a a short video which demonstrate to you how the process is like.

 

Self Alignment of SMT Components During Reflow Soldering

For those who had not experience in SMT soldering before, it can be intemiding. One common question is the concern of not placing the component perfectly on the board. While smaller component can be more changllenging to place, the good news is that you do not have to place the component with precision. As long as the component’s lead is touching the SMD pad on the PCB board, that would be good enough. The component will be pull to alighnment automatically during the reflow oven soldering process.

The following video demonstrate the self-alignment of the small SMD components during the reflow oven soldering process.

That’s All for SMT Soldering and Assembly

Simple isn’t it. Once you done it for a few times, I am sure you would not want to go back to through-hole components again.

This is not to say that through-hole components are no good. For connectors where there are a lot of physical handling with user plugging in and out, it is recommended to go for through-hole connector. The mounting will be stronger and is less likely to be damaged due to rough handling. Electrolytic capacitor is currently less expensive than the SMT version.

There are pros and cons working with SMT. I would say SMT has much more benefits compare to through-hole. It is definately a direction which you should move towards.