Solderability Test Experiment

As is well known, solderability is very important for the printed circuit boards, we must do solderability test of each batch PCB we made. In this way we can inspect the weldability of the PCB before we go ahead the assembly process, much helpful for SMT.

Today we are going to discuss the solderability test experiment. In order to explain it more clear, we now do a simple solderability test and show you all the steps.

1. Take a small solder pot, plug in the power, turn on the switch and heat the solder pot to a certain high temperature(about 8 minutes).

2. Put a tin bar to the solder pot, then you can see the tin bar is begin to melting, slowly into liquid tin, then more and more.
3. After few minutes, there will be enough melting liquid tin in the solder pot to do this test.
4.Use a tweezers to pick up a PCB circuit, first clean the PCB with rubbing alcohol. Because the unclear surface or the oxidation of the PCB will affect the test result.
5. This is the key step of this test, put the PCB into the solder pot, depth about 2 mm,time 4-5 seconds is ok. Then you can see the tin will go into the hole of the PCB.
6. Take out the PCB from the solder pot and put it into the cold water. After few seconds, you can see the experimental effect.

This solderability test is very simple and easy. We can see the results very soon. Our Best Technology did solderability of every batch PCB we made, and we also supply our customers with the solderability test report and the test samples.

The basic knowledge of PCB (2)

2. The classification of PCB

 (1) Single sided PCB

Single sided board means the conductor pattern appears only on one side. Because single sided PCB has many strict limits. On trace design, only circuit at early stage use this kind of boards.

(2) Double sided PCB 

Double sided board means the conductor patterns appear on both sides of the board. However if we use the conductor patterns on both sides, there should be proper circuit to connect two sides. The bridge between the circuits is called via. Those vias are plated with metal, such as tin, copper, gold, etc. Because the area of double sided PCB is two fold of the area of single sided, and the conductor pattern can cross with each other, so it suits to be used on more complex circuits.

(3) Multi-layer boards

In order to enlarge the area of conductor pattern, multilayer PCB uses more single or double boards. It uses several piece of double sided boards, and a dielectric layer is put between every layer of boards. The layers of one PCB represent the layer of conductor patterns. The amount of the layers is always even number. Technically we can make PCBs up to 100 layers.

 For via, if we use it on double sided PCB, the whole boards will be drilled. While on multilayer PCB, if you just want to connect some traces, via may will waste trace space of some layers. Then we use buried vias and blind vias to solve this problem, because they are only drilled through several layers.

a. Buried vias only connect inner PCBs, so we can’t see them from the surface.

b. Blind vias connects several layers PCB with surface PCB.

In multilayer PCB, the whole board directly connects the ground line and power (used for preventing affection of the transmission signals on the signal). So we divide layers into signal, power, or ground. If the components on PCB need different power supply, this kind of PCB would have more than two layers of power and wire layers.

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