Differences in Mounting Methods, Including Surface Mount Technology

Mounting refers to the process of connecting components to the fabricated PCB. A PCB only becomes electrically functional after this mounting process is completed.
This page explains the differences between surface mount technology and other mounting methods.

Common PCB Mounting Methods

Common methods for mounting components on a PCB include surface mount technology, where chip components are soldered to the exposed copper pads (lands) on the board surface, and through-hole mounting, where components are inserted into holes and then soldered in place.

Differences Between Mounting Methods

Surface Mount Technology (SMT)

Surface mounting is carried out in the following steps.

First, solder paste is applied. A stencil, known as a metal mask, is placed over the PCB, and a dispenser is used to apply solder paste precisely to the areas where chip components will be mounted.

Next, adhesive (bonding agent) is applied to fix the chip components to the board. This step is generally unnecessary if solder paste has already been applied. However, in cases where additional stability is required, both solder paste and adhesive may be used.

The chip components are then placed on the areas where solder paste or adhesive has been applied. The final step involves soldering and curing.

Soldering and adhesive curing are performed in a reflow oven. Once complete, the board undergoes inspection to ensure there are no connection failures, marking the process as finished.

Through-Hole Technology (THT)

Through-hole mounting follows the process below.

Leaded components are inserted into the through-holes of the PCB, either manually or using an automatic insertion machine. Before soldering, flux is applied as a pretreatment to improve solderability. Then, soldering is carried out to connect the board and the leaded components.

After soldering, the board is inspected for any connection defects, completing the process.

Mounting on Flexible PCBs (FPC)

Mounting components on flexible printed circuit boards (FPCs) generally follows the same basic methods as conventional PCB mounting. However, due to the unique characteristics of FPCs, there is one significant difference: their flexibility requires the use of stiffeners during the mounting process.

If a stiffener is not applied to the circuit area where components are mounted, there is a risk of solder peeling off or the circuit separating from the base material—especially during connector insertion or removal, or when soldering. In addition, the pressure applied during soldering may cause the mounting area to bend, leading to improper soldering or the detachment of mounted components.

Therefore, when mounting on a flexible PCB (FPC), a stiffener must be applied to the reverse side of the board.

Summary

Mounting on flexible PCBs (FPCs) requires the use of stiffeners. By attaching a stiffener with sufficient rigidity to the FPC, pressure on specific areas can be avoided,preventing solder or circuit detachment during handling or operation.