At present, there are two general FPC welding processes, one is tin press welding, and the other is manual drag welding.
It is generally recommended to use a tin press for pressure welding. The advantages are: smooth welding, less virtual welding, short circuit and other defects. Disadvantages are: high cost, board design needs to consider component layout. Below we mainly introduce the related processes of manual support welding:
Manual drag soldering is the manual use of an electric soldering iron and tin wire to solder the solder together. For FPC soldering, it is recommended to use an OKi soldering iron and a solder wire.
The main sequence of FPC welding is: FPC paste alignment - tin feeding and drag welding - visual inspection - electrical inspection.
FPC pasting alignment: Before pasting alignment, check whether the FPC pad and the corresponding solder surface are flat and oxidized. Note that after pasting, the pad must be exposed to about 1.00mm of pins, which is convenient for tinning.
Main control time and location
1. Time: Before tinning, the soldering iron must be placed on the pad for 2-3S, so that the FPC and the pad are fully heated, which can effectively prevent virtual soldering;
2. Position: The soldering iron and the gold finger are inclined at about 30 degrees.
There are four main control points for tin drag soldering:
1. Time: It is generally recommended that the time is calculated by 3S/the length of the soldering iron tip, which is about 4-10S;
2. Temperature: 290-310 degrees Celsius;
3. The position of tin feeding: the position of the tin is better if the tip of the soldering iron is inclined to the pad;
4. Strength: When the tip of the soldering iron is in contact with the parts, a little pressure should be exerted on the principle of not causing damage to the gold finger.
external assessment:
1. The tin point is formed into an inner arc;
2. The tin point should be complete, smooth, without pinholes, and without rosin stains;
3. There must be wires, and the length of the wires is between 1mm;
4. The FPC shape shows that the fluidity of tin is good;
5. Tin surrounds the entire FPC feet.