JLCPCB PCBA Service vs Hand Soldering

For the prototyping stage, it is common to assemble components by hand soldering. For small numbers of PCBs used for prototyping, this may be reasonable. But even for small quantities, hand soldering causes assembly problems quite often. Despite such possible short circuits, cold solder, or bulky soldering. hand soldering is still considered the most affordable option for decreasing development costs.

JLCPCB is becoming a game-changer in the PCB prototyping field. It provides PCBA Service at competitive pricing. The PCB designer can select electronic components from the component library of their preferred CAD software.

JLCPCB's PCB assembly price is high quality and affordable, and the economic savings that the user can obtain is great considering that the PCBs are ordered, and the components are purchased separately individually. If not accounting the value of time spent for hand-soldering by oneself. So, what makes us choose JLCPCB PCBA Service over hand soldering? It is the professional finish

Here are two common problem scenarios in handmade soldering.

Visible Fault: Shifted Component Placing Makes Pins Shorted

Two similar PCB models are shown here:

Fig 1: This PCB was soldered by hand, using the same components but the solder quality depends too much on the user's soldering experience, you can see a short circuit in the ESP32 module due to excess solder between two pins.

Fig 2: It is a PCB Soldered with the JLCPCB SMT Service, as you can see the soldering finishes are professional and the components are correctly aligned.

Fig. 3: Some pins of ESP32 module are shifted in and short circuited due to a poor choice of soldering iron tip, little use of flux or carelessness when applying solder paste.

That causes some pins of the ESP32 module not to make correct contact with the PCB and causes the microcontroller to not work, and therefore impossible to write its firmware until the pins are correctly resoldered.

However, when ordering 20 PCBs with the same specs using JLCPCB's SMT service none arrived faulty

Invisible Fault: Detached Pads on Component’s Bottom Side

Figure 4 is showing PCBs with UVC LEDs assembled. These UVC LEDs have solder pads on the bottom side, like BGA. For the first prototyping, I used JLCPCB’s PCBA service, and the prototype worked well as it was designed. (This text is written in the first person; it can be changed to the third person if it is a text to inform and not a written essay)


But the problem came from when I was making the second version of the prototype. I needed to move the LEDs to the other side, and I needed a quick solution. As the normal lead time for JLCPCB’s PCBA service was 10 days, I decided to assemble it by hand soldering. I ordered 10 bare PCBs from JLCPCB and received them in 3 days. And on the 4th day, I asked to assemble the LEDs and other components to a soldering technician, who had been working in a PCBA company for more than 10 years.

But to my surprise, 4 or 10 boards were buggy. Some LEDs were not operating.

Figure 5 shows one of the buggy boards we made. We tried to solder the LEDs several times again, but the success rate was very low. So, I had to use JLCPCB’s PCBA assembly service again. Due to a wrong decision, the project due date was delayed and expensed more budget.

(This may be due to a PCB design error, or errors in the technician's soldering due to not specifying if the tool used was the correct one, such as a soldering station heat gun, heating oven, or soldering iron. It could be easily verified if a fully manufactured pcb is made with the JLCPCB SMT service as a point of comparison, it is advisable to always consider the availability of electronic components used in the design before ordering the pcb to be manufactured with the JLCPCB SMT service).

Fig. 5: UVC driving board, assembled by hand soldering. Some LEDs are off because the bottom pads are detached and not soldered correctly.


What makes the hand soldering gives more faults than JLCPCB’s PCBA service? JLCPCB uses the normalized SMT assembly line, including pick-and-place machines and the reflow soldering process.

The pick-and-place machine is programmed as the design, it places components in the designed place. In hand soldering, it is not easy to set the soldering temperature in the right range. But in the reflow soldering process, the temperature of all the soldering joints is equally managed via hot gas and infrared. (Depending on the material, thickness and amount of copper on the PCB, the correct SMD soldering time and temperature may vary, you should always have adequate tools to carry out this process and avoid errors in handmade soldering).

In the past, using SMT assembly service for small quantities of prototyping was usually not economic due to high PCBA cost. But JLCPCB’s SMT assembly line is almost near to the bottom cost, still gives quality results.