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- September 30, 2022
- PCB knowledge
- (0)
- 06 mins
A detailed understanding of different aspects of bare PCB
Introduction
A bare printed circuit board (PCB) consist of conductive and insulating layers which are laminated together. The bare PCB is the basic building block of an electronic circuit. It provides conductive paths to electronic components and provides physical supports to the components design. Bare PCB can commonly be seen in our daily, whether you are using a TV remote, smartphone, washing machine or a self driving car.
What does bare PCB mean?
A bare board is nothing but a PCB on which electronic components are not soldered, i.e. a bare board is a laminated sheet of PCB substrate, metal coating, conductive pathways and patterns. A bare board can be a through hole board or an surface mount technology(SMT) board.
A through hole type PCB is defined as, when electronic components lead are soldered after their conducting lead are pass through the holes of bare board. Normally, in through hole type bare board electronic components are fixed on one side and soldering is done on the other side.
Whereas, the most commonly found surface mount technology(SMT) type bare board are which, electronic components are placed on the surface of bare board such that their conducting lead are placed upon specified solder round patches on which they are soldered.
What are the six types of bare PCB?
Before manufacturing PCB it made sure how many layers are required in bare board. The number of layers increases with the complexity of gadget or device to be made. Simple gadget requires single layer PCB which does not cross over connection feature in it. Cross over connections can be easily made in double layer or multi layer PCBs. There are six types of bare PCB which are mention below:
Single Sided PCB
The most simplest or basic bare PCB is single layer PCB which is made a single layer of conductive material cover by copper overlay and after lamination solder mask is use to make electrical contacts with electronic components.
Double Sided PCB
The double layer printed circuit board contains two conductive layer mounted on both sides of the board. Therefore, wired connections between layers are possible on this board.
In double layer PCB components are solder on both sides of the board which provides large surface area for circuit. These PCBs are more useful for modern gadgets or devices which perform complex function such as air conditioners.
Multilayer PCB
In today’s market, these are probably the most outstanding PCBs. It is now possible to make profoundly complex tech gadgets thanks to the high levels of performance associated with multi layer motherboards. Multi layer PCB ranges from 4 to 10 layers PCB which are also used in satellites, supercomputers, etc.
Rigid PCB
A rigid PCB is most simple bare board which are normally used by students and hobbyist. It provides rigid base layer for electronic components due to glass present in its non conducting layer. It has decent thermal resistance. A rigid PCB cannot be bend or fold.
Flex PCB
The flex PCB uses flexible base material like polyimide which allow it to withstand vibration, dissipate heat and fold up into different shapes. It easy found in LED and LCD displays of TV, smartphone, etc.
Rigid-Flex PCB
A rigid flex PCB is a combination of both rigid flexible substrate. It uses flexible polyimide material on copper cladding for substrate. Thus, it is capable of bending, twisting and folding. It is commonly use in industrial, military, commercial and medical applications.
What are the materials used in bare PCB?
The material used to fabricate the PCB determines its performance and level of integration. The performance of material effected by temperature, adhesion, tensile strength, flexibility, dielectric strength, etc. The three materials which are commonly used are:- FR-4
- PTFE (Teflon)
- Metal
The manufacturing process of bare PCB”
Bare printed circuit boards are bare bone of all electronics. After a design is check on software , then it’s time to to put the design on PCB. It is necessary to know the manufacturing process of PCB to prevent any future errors. The steps of manufacturing bare PCB are as follows:
- Design and output
- From file to film
- Printing the inner layer
- Removing the unwanted copper
- Layer alignment optical inspection
- Layer up and bond
- Drilling of PCB
- Plating and copper deposition
- Outer layer imaging
- Plating
- Final etching
- Solder mask application
- Surface finish
- Silkscreen
- Electrical test
- Profiling and V-scoring
What are the advantages of bare PCB?
Bare PCBs are inexpensive and highly reliable. For high-volume manufacturing, wire-wrapped and point-to-point constructed circuits are much cheaper and quicker, but require more layout effort. The high volume production is easier because production and soldering can be automated.The usage of bare PCB Boards
Bare PCB board are integral part of electronics devices on which our daily life heavily depend upon. These devices are can be easily found in medical, consumer electronic, industry, LEDs, aerospace, etc.The most common examples in our daily life are LED light, microwave oven, washing machine, medical instruments, air conditioner, smartphones, etc.
The importance of bare PCB testing
The bare PCB board manufacturing includes electrical testing step which is crucial to verify the final product and prevent damaging of electronic components. Although the bare PCB testing looks time consuming and costly but compare to its other manufacturing process and testing importance cost is minimal and time is less valuable then proper working of PCB.- A continuity test verifies that the circuit has no open points.
- During isolation testing, two separate electrical connections must have the required resistance.
What are the 7 types of bare PCB testing methods?
PCB assembly testing is an integral part of the manufacturing process. A reputable electronics contract manufacturer (ECM) will offer a variety of PCB testing methods, but there are seven main types:
In-circuit testing
A fixed probe is used in this test that corresponds to the layout of the PCB.Solder connections are checked with probes.During this test, fixed probes are laid out in a way that matches the PCB design. The integrity of the solder connection is checked by a probe.On the nail bed, the board is pushed down on the probes to start the test.
Flying probe testing
Flying probe testing is less expensive than In circuit testing. It is a non powered type of testing which checks opens, shorts, resistance, inductance and capacitance. In this test, needles attached to a probe are placed on an x-y grid obtained from basic CAD. The ECM program coordinates with the circuit board and then runs.
Automated optical inspection (AOI)
To take photos of the PCB, AOI uses either a single 2D camera or two 3D cameras. The program compares the board with the captured photos. It then check whether there is some changing or not and raises flag alarm. It detects fault early to stop production on time .
Burn-In testing
It’s an intense type of PCB testing in which maximum specified power is pass through the circuit to detect early failures. It is normally carried out for medical and military applications where rough working environment is found. It shortens the life span of circuit, so after few successful attempts the power is reduce to for other testing PCBs.
X-ray inspection
It is an inspection tool of bare PCB. An X-ray technician locate defects by applying radiation on PCB to find defects in solder connections, internal traces and barrels.
Functional testing
It is an old-fashioned way of testing circuit. It requires external components and power supply to check functionality of the circuit. It save money but waste time.
Pinned fixture testing
In a pinned fixture test spring loaded pogo pins check all of the boards connective surfaces. thousands of points can be tested at one time. It is more efficient than flying probe test.
