Question 1

¿Por qué PCB es verde?

Accepted Answer

Solder mask is a protective layer of polymer. It function as a mask layer by forming a protective coating on PCB. The main purpose is for preventing copper trace on PCB from contamination. Furthermore, by covering solder mask on copper trace could prevent broken trace. (Some exposed pads might risk falling out and solder mask could minimize the situation). The solder mask is moisture proof and can provide insulation, resistance, heat endurance and to maintain appearance.
Solder mask, also known as solder resist. Though 99% of PCB use green solder mask, there are other solder mask color available for consideration, such as red, black, blue and so on.
The most common used PCB solder mask is made of Epoxy Liquid. It is typically applied using silkscreen techniques onto the top and bottom side of PCB, where the soldering is not required. In some occasions, the PCB manufacturers might apply inkjet printing technology.
In general, most of PCB manufacturers would apply the lacquer on entire PCB and then put in the oven during pre-baking process and then exposure the film by using contact-exposure technology to transfer the image onto the solder mask layer.
The process of solder mask seems fairly easy. However, if the solder mask is not applied properly during PCB manufacturing process, it might cause some quality issues, such as contamination, skip printing, copper exposure, unequal printing etc. Moreover, the thickness and displacement of solder mask could have affected the quality of tin soldering during SMT.

Question 2

¿Qué significa PTH/ Vías NPTH en PCB?

Accepted Answer

If you look closely at the printed circuit boards (PCB). You will see that there are many holes with different size on the boards. Those holes on PCB can be simply divided into two types: PTH (Plating Through Hole) and NPTH (Non Plating Through Hole).
The easiest way to distinguish between PTH (Plating Through Hole) and NPTH (Non Plating Through Hole) in PCB is to see if there are any traces of plating on the borehole wall in the PCB.
NPTH (Non Plating Through Hole) refers to a hole without copper in the borehole wall. It is generally used as the positioning hole and screw hole of PCB. The hole diameter is usually larger than PTH.
PTH (Plating Through Hole), the borehole wall has a layer of copper, the PTH holes on PCB has two purposes:
1. Used as component hole for welding DIP components, the hole diameter must be larger than the pin of the component, so that the component can be inserted in the PTH.
2. Another relatively small PTH (Plating Through Hole), also known as “Via”, can be used to connect and conduct wiring between different layers in PCB.

Question 3

Maneras de Fabricación a PCBA

Accepted Answer

PCB production is a complicated process, especially PCBA. There are some ways to produce PCBA from PCB, such as SMT, DIP, etc.

First, we will introduce how to produce PCBA. PCBA means Printed Circuit Board + Assembly. That is to say, the SMT or DIP process for PCB bare board, is called PCBA.
SMT and DIP are both the process that put the components on the PCB. The main difference is that it is no need to drill holes for SMT; but DIP needs to put the components’ PIN into the drilling holes.
DIP, plug-in component, which means to plug in the component on the PCB. Due to the larger dimension of the component, when it cannot use mount or SMT, it will use DIP. There are manual plug-in and automotive plug-in currently.
The main process for DIP is adhesive pasting (Prevent tin plating from undesirable places), component plug, inspection, wave soldering, board brushing(remove stain caused during wave soldering), and production inspection
DIP is also known as dual in-line package. The shape of the integrated circuit is rectangular, and there are two rows of parallel metal pins on both sides, called pin headers. The components of the DIP package can be soldered into the plated through holes on PCB, or inserted into the DIP socket.

Question 4

¿Comó elegir el material de PCB?

Accepted Answer

Selecting a suitable printed circuit board materials is one of the most important parts during PCB manufacturing. To understand the differences of printed circuit board materials will help you to better choose a suitable PCB material for your products in order to optimize the performance of the application.

The printed circuit board materials are typically comprised of epoxy resin, glass fiber (reinforcement) with a copper foil.
The type and the amount of resin contain will affect the printed circuit board materials properties. Therefore, it’s better to select the printed circuit board materials that align with the desired PCB design.
Currently, the most common printed circuit board materials for the substrate of a PCB is FR4, a flame retardant grade.
The following are the most common printed circuit board materials that used in PCB manufacturing industry.
FR4: Glass fiber + epoxy. (The most commonly used printed circuit board materials), High TG FR-4, CEM-1, CEM-3 etc.
There are some elements that need to take into consideration while choosing the printed circuit board materials. For example, the required TG for final products, the rate of CTE, the flatness of PCB and heat endurance during the SMT process (risks of temperature rising).

Question 5

¿Qué significa ¨X-out¨ en la industria PCB?

Accepted Answer

In the PCB industry, the term “X-out” also known as “Cross-board” and “X-board”. It stands for the defective boards in PCB panels, and X marks are usually marked on the top.
Normally, the SMT factory will not allow X-out boards appear in PCB panels, because it cause the loss of efficiency during the process of SMT. However, the X-out boards is inevitable while producing PCBs, the more PCBs in one single panel, the more likely X-out boards appear.
The Acceptable Quality Level (AQL) for X-out boards in the PCB industry, generally, the number of X-out boards must be less than 20% of the number of PCBs in a panel. That is, in a panel with 4 pieces of PCBs, only allowed 1 X-out board in it. In a panel with 8 pieces of PCBs, only allowed 2 X-out boards. And the total amount of X-out boards must be less than 10% of total PCB shipments.
When about to ship the PCBs, must be assured that in each vacuum bag, the position of X-out boards must be the same position in each panel. If the X-out boards less than the quantity of the whole package, it must be packed in the mantissa box, and clearly marked with the total quantity of PCBs and X-out boards and relevant information.
If the buyers allow X-out boards to exist in PCB panels, the SMT factory can skip the X-out boards without doing SMT process by modifying the SMT program or by identify the bad marks on PCBs. But it will cause the SMT efficiency loss.
If the buyers will NOT allow X-out boards to exist, it means the PCB manufacturers are forced to produce more PCB panels, in order to eliminate the PCB panels, which has X-out boards in it. Therefore, the purchase cost will increase, but the SMT process will achieve the maximum of efficiency.

Question 6

Los buenos y los malos del dedo de oro y su aplicación en el PCB.

Accepted Answer

Gold finger is the metal connector on the PCB, and gold finger is also known as Gold tips or Gold tabs.
Gold fingers are the gold plated connectors on the edge of PCB that arranged like fingers. During PCB manufacture process, gold finger will be coated with a layer of gold through a special process on the copper cad lamination. However, today, many PCB designer has replacing the surface finish of gold finger by tin plating.
For PCB designer, the aim of gold finger is to connect the PCB by compressing the corresponding slots with connector, which allows its to communicate with one device to another.
The advantages of using plating gold on gold fingers for the PCB: The gold finger can resist oxidation and it is durable with high conductivity.
The disadvantages of gold finger on the PCB: it has relatively uneven surface, the needs of connecting line and the price of gold finger is extremely expensive.
The difference between applying immersion gold and plating gold on the gold fingers is that immersion gold is easier to solder compare to plating gold and will not affect the signal, it is also hard to get oxidized. However the immersion gold is less durable.

Question 7

Ventajas y Desventajas del Tecnología de montaje superficial (SMT)

Accepted Answer

SMT is a technology that uses electronic components to mount on the PCB.
SMT is to print solder paste on pad then place the electronic components on it. Next, we heat up to liquefy the solder paste and wait for cool down. After cool down, those electronic components will be mounted on the PCB.
SMT can make electronic product’s design become more delicate because the size of electronic components is small, this can reduce the size of PCB significantly.
SMT is suitable for PCB mass production because SMT supports automated production also the SMT production is a lot more stable than DIP.
SMT can reduce the labor cost and operating hours for manufacturing the PCB.

Question 8

Oro Duro VS Chapado En Oro Suave

Accepted Answer

Plating gold is a type of PCB surface finish, also known as nickel gold electroplating.
In the PCB manufacturing process, plating gold is to deposit a layer of gold plated over a barrier coat of nickel by electroplating, which give it a name of nickel gold electroplating.
Plating gold can be divided into ''hard gold plating'' and ''soft gold plating''. The PCB manufacturer has to take the characteristic of the two types of gold into consideration during PCB designing.
In PCB gold plating process, hard gold plating is also referred to as a plating alloy. It has been alloyed with other elements which makes it harder, whereas the soft gold plating is pure gold.
Plating gold application in PCB manufacturing. Hard gold plating is suitable for use in places where the force of friction is needed such as gold finger, keypad. Soft gold, is typically used for aluminium or gold wiring on COB (Chip On Board).

Question 9

¿Por qué se usa V-CUT en el diseño del PCB?

Accepted Answer

Because the strength and hardness of PCB.
After finishing the pc board assembly, in order to fit the PCB into the end product. The PCB manufacturer will design V-Cut to de-panel the PCB
Those dividing lines that were cut by cutter on the PCB is called V-CUT and it is commonly seen between break-away rail and unit on PCB.
It is literally impossible to de-panel PCB with your hands.
Even if you do break the PCB manually, the electronics circuit board parts will be damaged.
When bending the PCB, the application of the force will cause PCB deformation which might result in the electronics circuit board parts cracked.
If thickness of PCB is too thin, we do not suggest to do V-CUT because it will damage PCB structural.

Question 10

¿Por qué hornea el PCB que se ha producido a largo plazo?

Accepted Answer

The purpose of baking is to remove the moisture from the PCB.
No matter the PCB is at production site or still in vacuumed package, both would increase the risk that PCB can absorb moisture.
If PCB is stored at a bad storage condition or over storage period, these would also make the PCB absorb moisture easily.
The high temperature would cause inner board moisture evaporation when assembly the damp PCB.
The PCB will have blister or delamination due to steaming.

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