LED (Light Emitting Diode) lighting is an important part of the energy saving and environmental protection industry.
The equipment and process method of LED surface assembly are basically the same as those of SMT processing. Mainly, the production line for producing large-size LED advertising display panels requires large-scale printing, SMT placement, and reflow soldering equipment. There are no special requirements for the accuracy of these devices, but printing paste and reflow soldering processes must be optimized and process controlled.
I. Requirements for manufacturing equipment for 1.2m and 1.5m large LED board mounting production lines
(!) 1.2m, 1.5m long LED lamps and large-size display solder paste printers.
(2) The minimum requirements of the placement machine can be a 1.2m large LED board.
LED placement machine does not have high requirements for placement accuracy. It is different from traditional placement machines in that it must have 3 conditions:
① 1.2m large LED board mounting, so the minimum mounting size must reach 1.2m;
② LED placement machine is more important for color difference control. The best efficiency is to take LEDs on a roll tray (single
LED board has no color difference);
③ LEDs are generally produced in large quantities, so the mounting speed should be fast, and the minimum requirement is more than 18000 points per hour.
(3) LED reflow soldering furnace is better than eight temperature zone.
Second, the solder paste for LED
Due to the fact that some materials of LED lamps can only withstand high temperatures around 150 ℃, low temperature lead-free solder paste should be used.
Due to long-term exposure to the sun and south shower in LED displays, it is required to have sufficient toughness on the solder joints of the LED display board.
Therefore, 96.5Sn3.0AgG0.5Cu and 99Sn0.3Ag0.7Cu high-temperature lead-free solder paste must be selected. Its tin-silver-copper alloy composition can effectively improve the "relatively brittle" deficiency of low-temperature solder joints and improve solder joint reliability.
In the case where the customer does not have environmental protection requirements, 63Sn37Pb leaded solder paste can be used.
Third, the reflow soldering of LED assembly board
If the carrier board is not used, the FPC is directly placed on the network chain and passed through the reflow furnace. The rate of point defects such as tombstones is high. After FPC baking,
The FPC is placed on the board and reflowed, and the defect rate of solder joints such as tombstones has improved.
Suggestion: Use the carrier board to slowly warm up and fully preheat, and carefully optimize the temperature curve to reduce the defect rate of solder joints such as tombstones.