Q: Precautions for PCB manufacturing in extreme environments

Compared with electronic products used in ordinary environments, electronic products used in extreme environments need to meet higher manufacturing requirements. As the core of electronic products, PCB is extremely important in controlling its performance. PCB materials must be fully considered in PCB manufacturing and layout. As far as extreme environments are concerned, materials that can withstand extremely high temperatures should be selected, such as FR4-008 or PI.These materials can not only withstand extremely high temperatures, but also won't cause the solder mask to detach. Since PCBs that will be used in extreme environments usually have to withstand extremely high heat and temperature fluctuations, the board should be prevented from warping, otherwise it may cut off the circuit, damage the solder joints, and cause problems during the application process. During the PCB assembly process, inspections must be carried out to ensure the quality of the final product. For example, AOI instruments should be used to check the performance of solder joints. The solder paste thickness meter is used to determine whether the solder paste has the best thickness, and whether the thickness is helpful for smooth reflow soldering in the subsequent steps of SMT assembly.

Question 1

¿Por qué es OP es importante de la producción PCB?

Accepted Answer

When having discussion with PCB maker, you must have had heard that PCB factory is following the specification and instruction in OP when producing the PCB of your design.

OP is the producing standard that engineer inputs all your requirements into. It is like an ID of your PCB design. Including the PCB size, layer count of PCB, copper thickness of inner layer and outer layer, surface finish type, solder mask color, silk screen color, V-cut or mouse-bite, quality level requirement, and other types of requirement that is related to your PCB design.

So is OP important to the PCB production? The answer is surely positive because all things related to PCB fabrication is based on this OP!

Question 2

What is a printed circuit board (PCB)?

Accepted Answer

Do you have a rudimentary understanding of what a printed circuit board (PCB) is and what industry do you think has a close relationship with a printed circuit board (PCB)? There are various industries, the following five types are the main ones. Please look.

Printed circuit board for cars (PCB):
Electronic systems for cars are fairly complex, but still have development potential in the global market. The development of printed circuit boards (PCBs) for automobiles depends on the speed of development of autonomous driving.
server:
2020 is the "first year of 5g", where big data and 5G related information have been flying for the past few years, so the demand for printed circuit boards should rise in the era of data explosions.
Wearable computer:
For the past few years, wearable computers have been seen as good expressions such as exercise type, medical type, and electronic consumption type.
Laptops, TVs:
Unlike mobile phones, the laptop and TV markets are nearing saturation. It's still mainstream, but future growth isn't optimistic.
cell phone:
Mobile phones have always played a leading role. Although the growth rate in recent years is gradual and negative growth is possible in the future, the development of science and technology has a consistent spirit of improvement. In the future, mobile phones will be able to integrate more functions and evolve in more precise and higher directions. Therefore, it cannot be said that the demand for mobile phones for PCBs will surely decrease.

Question 3

Precautions for PCB manufacturing in extreme environments

Accepted Answer

Compared with electronic products used in ordinary environments, electronic products used in extreme environments need to meet higher manufacturing requirements. As the core of electronic products, PCB is extremely important in controlling its performance.

PCB materials must be fully considered in PCB manufacturing and layout. As far as extreme environments are concerned, materials that can withstand extremely high temperatures should be selected, such as FR4-008 or PI.These materials can not only withstand extremely high temperatures, but also won't cause the solder mask to detach.

Since PCBs that will be used in extreme environments usually have to withstand extremely high heat and temperature fluctuations, the board should be prevented from warping, otherwise it may cut off the circuit, damage the solder joints, and cause problems during the application process.

During the PCB assembly process, inspections must be carried out to ensure the quality of the final product. For example, AOI instruments should be used to check the performance of solder joints. The solder paste thickness meter is used to determine whether the solder paste has the best thickness, and whether the thickness is helpful for smooth reflow soldering in the subsequent steps of SMT assembly.

Question 4

PCB applies in smartwatch (Wearable devices)

Accepted Answer

Common smartwatches include Apple Watch/Garmin/Xiaomi bracelet (ExPlus also makes related wearable devices! Bluetooth headsets/police equipment, etc.)

Wearable devices have the characteristics of light weight in appearance, and the product itself also has the four major characteristics of integration, lightness and softness, wireless, and universal use. In order to meet the electrical requirements of wearable devices, it is necessary to use SiP chip carrier boards and 3D IC chips. High-end PCB technology such as carrier board, hard board with embedded active/passive components, high bending resistance FPC and Low Dk & Df PCB materials.

The wearable application industry is divided into five categories: Healthcare and Medical, Fitness and Wellness, Infotainment, Industrial and Military.

To put PCB in the smartwatch, and due to the small space, fewer components, and less memory configuration, most of the designs are designed with a flexible board or a combination of rigid and flexible boards.

Nowadays, wearing a smartwatch is like having a personal digital assistant. The functions that can be processed are: camera, thermometer, compass; GPS; heart rate monitoring, diving computer, etc.

Question 5

What is HiPot Test?

Accepted Answer

HiPot test, also called insulation withstand voltage test, is a non-destructive reliability test that can measure the "breakdown voltage" and "insulation resistance" of PCB products. High voltage will be applied to PCB products within a certain period of time, usually 1.5KV~3.0KV (daily power consumption is 110V or 220V several times the voltage, the conditions and standards vary depending on the product) to test the electrical safety of PCB products whether the characteristics and insulation performance are qualified, under high voltage, some materials with poor insulation will be broken down and a short circuit will appear.

The HiPot test is carried out by allowing the input power terminal of the PCB product to withstand a high voltage for a limited period of time, and measuring its collapse state. This test stipulates that the PCB "Does not allow arc breakdown or collapse during the period when a high voltage is applied.

The HiPot test can also detect potential defects in PCB products, such as:
1) The insulating effect of the insulating material is not good
2) There are pinholes on the insulator
3) Insufficient electrical clearance between components
4) The insulator is squeezed and broken

Question 6

¿Qué es Soldado (bonding) en PCB?

Accepted Answer

Bonding, that is, chip bonding, chip coating. Bonding is a wire bonding method in the chip production process. It is generally used to connect the internal circuit of the chip to the package pins with gold wires before packaging.

What will be done after bonding (after the circuit is connected to the pin)?
The chip is packaged with glue, and use the packaging technology, COB (Chip On Board). The tested wafer is implanted on a special circuit board, and then the wafer circuit is connected to the circuit board with a gold wire, then after melting, the organic material with special protective function is covered on the wafer to complete the later packaging of the chip.

What are the advantages of Bonding?

The bonding chip is anti-corrosion, anti-vibration, and stable performance:
The advantage of this packaging method is that the stability of the finished product is better than that of the traditional SMT patch method. Because the circuit board is affected by moisture, natural and human, it is prone to short circuit and open circuit. The bonding chip is protected by organic materials, and isolated from the outside, there is no moisture, static electricity, and corrosion.
Bonding wafers are suitable for mass production: The product has strong consistency and long service life. This packaging technology has the advantages of low cost, space saving, light weight, good heat dissipation, and simple packaging method.
Application of bonding:
Many of the LCD screens of mobile phones, PDAs, MP3 players, digital cameras, and game consoles will use bonding.

Question 7

What’re the pro and con with OSP surface finished

Accepted Answer

The OSP is kind of PCB surface finish that complies with RoHS certification.
The OSP is a chemical substance to cover the PCB surface with a layer of protective film on the copper surface.
The features of the OSP are anti-oxidation, heat-resistance and moisture-resistance. It can prevent PCB surface from copper oxidation effectively.
The advantages of PCB surface finish that applies with OSP are easy process, flat surface, eco-friendly and lower cost.
The disadvantages of PCB surface finish that applies with OSP are having shorter shelf life and easier to be scratched.

Question 8

¿Qué es Oro de la inmersión (Immersion Gold) ?

Accepted Answer

Before introducing immersion gold, we would like to talk about ''surface finish'',.

Surface finish is the "small movements" made on the surface during various metal processing. It is easier to understand the way of painting and covering other materials. An iron railing painted with paint is one of the practical applications of surface finish.

"Immersion Gold" means "nickel immersion gold", which is one of the surface finish for PCB. Immersion gold is cheaper than gold plated, so the shiny part of electronic parts is usually immersion gold. A thin layer of gold prevents oxidation of copper.

The characteristic of immersion gold is that it can attach "nickel" and "gold" to the copper sheet without cumbersome electroplating, and it is much smoother than gold plated. It is very important for the development of smaller and smaller electronic parts and parts that require high flatness.

Question 9

IPC Standard

Accepted Answer

Generally, the industry is divided into three categories with IPC as the standard, among which Class 2 is the standard.
Class1 consumer products, general electronic products and electronic peripherals
Class2 high-performance electronic products, communication equipment, commercial equipment
Class3 high reliability products, military applications

If the customer has no specific requirements, ExPlus follows Class2, IPC-6012 as the standard to ensure the quality of its materials.
High-quality PCB needs to meet:

In addition to the trace width, thickness, and spacing of the high-quality PCB should meet customer requirements to avoid trace heating, open and short circuit. The copper on the outer layer of the PCB must not be easy to fall off and oxidize, otherwise the PCB will be damaged soon after oxidation.
The PCB should not be easily deformed to avoid deformation of the PCB shell and misalignment of the screw holes after installation. Now it is installed mechanically, and the position of the PCB hole and line error and position should be within the allowable range.
The PCB should consider the high temperature, high humidity or other special environment required by the customer without additional electromagnetic radiation. The surface performance of the PCB should meet the subsequent installation requirements.

Generally speaking, a small volume of PCBs will use flying probe testing due to cost considerations, while mass-produced PCBs use fixtures to detect open and short circuits. In addition, visual inspection of PCB appearance, characters, solder mask, bevel, hole break, V-CUT, etc. are also necessary procedures before shipment.

Question 10

¿Qué es HASL en PCB?

Accepted Answer

HASL boards, Hot Air Solder Leveling, is to spray a layer of tin on the surface of the copper foil to protect the copper foil, and then use hot air to form an air knife to level the tin surface. There are two common spray Tin equipment, vertical and horizontal.
HASL used to dominate the PCB surface treatment process, which is an excellent process for larger components and wires with larger spacing.
However, the industry is gradually reducing the use of HASL because it is relatively dirty, unpleasant and dangerous in the process. The trend of lead-free has begun in recent years, which has further restricted the use of HASL. Although there is a so-called lead-free HASL, it involves issues such as equipment compatibility.
Advantages of HASL:
1. Because the plating layer itself is tin, a better Wetting effect can be obtained.
2. HASL is also low in price and good in welding performance, usually only for the first side, not necessarily for the second reflow side.
3. Long storage time and mature technology; suitable for visual inspection and electrical measurement.
Disadvantages of HASL:
1. Not suitable for welding fine gap pitch and too small parts because the surface flatness of HASL is not good.
2. It is easy to have solder bead in PCBA process, and it is easy to cause short circuit to fine pitch parts.
3. When used in the double-sided SMT process, since the second side has passed the first high-temperature reflow soldering baptism, it is very easy to spray tin and re-melt to produce tin beads or similar droplets that are affected by gravity and drop into spherical tin spots. In addition, the second reflow surface may also cause tin oxidation and IMC generation in advance to affect solderability during the first reflow.

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