Typically, there are two methods used for putting together a prototype circuit board. The first one is called the Surface Mount Assembly and the other is called the Through Hole Construction. There are two other types of circuit assemblies that are commonly used and related to the prototype circuit board. These are called the integrated circuit and the hybrid circuit. Let’s look at these four types a little closer to give you a better idea of prototype printed circuit boards.
The Surface Mount Assembly
This method of producing electronic circuits to made by mounting the components right on to the circuit board. This is more commonly used that through hole construction technology but both types of technology can be used on the same board simultaneously.
The circuit board is typically flat and made of tin lead, silver or gold plated copper pads that are called solder pads. The solder pads are coated with solder paste with is a sticky mix of flux and solder particles. A stainless steel stencil or a nickel one is usually used in this process. After this part, the boards go to a conveyor belt to go in to the reflow soldering oven. After being pre-heated, the boards go from there to a high temperature that melts the solder particles. This bonds the leads to the pads.
If the prototype circuit board is two sided, then once one side is completed and allowed time to set and dry, the reflow process is repeated on the other side.
Once both sides are complete, the boards are inspected for any components that may have gotten misaligned or parts that are missing. If they need to be repaired, they are sent to a rework station to correct any errors. After this they are sent to a testing station to make sure that they are functioning properly.
Through Hole Construction
This technology is done but using lead on the components and drilling holes into the circuit board as well as the soldered pads like the surface mount assembly technology.
This technology allows for extremely strong mechanical bonds compared to SMT methods but the drilling that is necessary makes the production process more expensive. It also limits the amount of routing area on the layers that are right below the top layer because the holes have to be able to go all the way through to the other side. Because of this, through hole technology is usually only used for much heavier components in larger packages.
When making a prototype circuit part, many engineers prefer this methods, however, because it is very compatible with breadboard sockets which is what is typically used. However, they often combine techniques in this case.
Integrated Circuit
An integrated circuit or IC is typically made out of a semiconductor material and used for a variety of different devices such as microprocessors and automobiles. An integrated circuit is determined by how many transistors it has. Prototype PCBs use this method if a small board is being made and does not need to handle large packages or bulkiness.
Hybrid Circuit
This is similar to an integrated circuit but is a miniature circuit made of individual devices. These devices are bonded to a printed circuit board using epoxy.
The difference between hybrid and integrated circuits is in how they are put together and manufactured. Hybrid circuits contain components that can not usually be included in some parts of the process in the making of prototype circuit boards.
There are some modern types of hybrid circuit technologies that allow the embedding of components in between the multi layer substrate making a three dimensional circuit. However, in order to do this, the components have to be placed on the top of the substrate.
Thick Film Technology
Thick film technology is often used in conjunction with hybrid integrated circuits which is the combination of integrated circuit methods along with hybrid techniques. This is when screens are printed on thick film and used to interconnect the technologies. When using this method, circuit designer has total freedom when choosing a resistor value which make manufacturing much easier. This technology has been around since the 1960’s when Ultra Electronics made circuits using a Silica Glass mixture with a film of tantalum. It was replaced by separated hybrid and integrated circuit board manufacturing.
