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Full turnkey printed circuit board assembly

Publish Date:2020-11-14

    As for the full turnkey printed circuit board assembly, I believe all electronic workers are familiar with it. It is an indispensable and important part of modern electronics. How much do you know about its production process? Let’s take a look at it.

 The substrate of the printed circuit board itself is made of insulating and nonbinding materials. The small circuit material visible on the surface is copper foil. In the circuit board’s manufacturing process, the remaining part of the circuit board is etched into a small part.

 These circuits, called wiring or wires, provide circuit connections to the parts on the circuit board. The color of the printed circuit board is usually green, which is the electric welding mask’s color. It is an insulating protective layer that can protect the copper wire from welding to the wrong place.

Full turnkey printed circuit board assembly

 The full turnkey printed circuit board assembly process begins with a PCB “substrate” made of glass epoxy resin or similar material. The first step is to draw the lines between the parts. The negative electrode of the printed circuit board is printed on a metal conductor by negative migration.

 Laying a layer of copper foil can eliminate the extra layer. Both sides of double-sided board production should be covered with copper foil, but two double-sided boards can be made with a special adhesive and pressed together to make multilayer boards.

 Next, we can drill holes and electroplate components on printed circuit boards. After the mechanical equipment is drilled according to the drilling requirements, the hole wall lining must adopt the plating through-hole technology (PTH). Ensure that the internal lines of each layer of metal treatment in the hole can be connected.

 Before electroplating, impurities in the hole must be removed. This is because the epoxy resin will produce some chemical changes after heating, it will cover the inner layer of PCB, so it should be removed first. Cleaning and electroplating operations are carried out in a chemical process. Next, you need to cover the outermost wire with a solder mask so that the wire does not touch the plated part.

 Then, each component’s marking screen is printed on the circuit board to mark each component’s position. Do not cover any wires or gold fingers because it will reduce the current connection’s stability or solderability. Also, if there is a metal connection, the gold finger’s position needs to be plated with gold, which can ensure a high-quality connection current when inserting into the expansion slot.

 Finally, the test. To test the full turnkey printed circuit board assembly for short circuit or open circuit, an optical-electronic test can be used. Optical scanning is used to detect defects in each layer, while electronic testing usually uses flight probes to check all connections. The electronic test is more accurate when short circuit or open circuit, but the optical test is easier to detect an incorrect gap in the conductor.

Ideaspcb explained the characteristics of SMT solder.

In SMT chip processing, solder can be divided into tin-lead solder, silver solder, and copper solder according to its components. It can be divided into high-temperature solder and low-temperature solder according to the ambient humidity. In the assembly of electronic products, tin-lead series solder, also known as solder, is generally used.
The characteristics of SMT Soldering are summarized as follows:

  1. Good conductivity: because tin solder is a good conductor, its resistance is minimal.
  2. It has strong adhesion to component lead and other wires and is not easy to fall off.
  3. Low melting point: it can melt at 180 ℃, easy to weld.
  4. It has a certain mechanical strength: the strength of the tin-lead alloy is higher than that of pure tin and lead, and because the weight of electronic components is light, SMT chip does not require high strength of solder joints so that it can meet the strength requirements of solder joints.
  5. Good corrosion resistance: the welded circuit board can resist atmospheric corrosion without any protective layer, thus reducing the process flow and cost.
  6. Because tin-lead solder is composed of more than two metals in different proportions, tin-lead alloy performance will change with the change of tin-lead ratio. To make the solder ratio meet the welding needs, it is essential to select the appropriate ratio of tin-lead solder.
  7. The solder shapes are wafer, strip, ball, solder wire, and so on. The commonly used solder wire is sandwiched with solid flux rosin.
Full turnkey printed circuit board assembly