Pulsed-Heated Hot-Bar Reflow Soldering is actually a selective soldering process where two pre-fluxed, solder coated parts are heated to your temperature sufficient to cause the solder to melt, flow, and solidify, forming a lasting electro-mechanical bond between your parts and solder. Pulse heated soldering is different from the traditional soldering process in that the reflow of solder is accomplished using a heating element known as a thermode which happens to be heated and cooled off for each connection. Pressure is applied through the entire cycle including heating, reflow, and cooling. This method is mostly utilized to connect flexfoils to Printed Circuit Boards.
With Automatic soldering machine is applied in the entire cycle,including heating, reflow and cooling. Because pressure is appliedduring the total cycle, the process is very ideal for parts that could jump loose during cooling down when soldered along with other techniques. Typical application examples are flexfoils, small wires, very light or small components, etc. The positioning of the parts is very accurate for the reason that pressure is applied during cooling down. For components which need an extremely precise positioning after being soldered HBR Soldering is the most ideal process.
And instead of traditional soldering, pulse-heated soldering reflows solder by using a thermode that may be heated and cooled down for each and every connection. This selective heating-up of merely a small portion of the components helps to make the process very suitable for soldering heat-sensitive parts. Typical application examples are CCD camera chips, connectors, etc.
With HBR Soldering all connections to become made simultaneously. As much as 200 leads or wires can be connected in a single process cycle (typically around 15 seconds). Making the connections simultaneously also prevents one wire jumping loose while
soldering the neighboring one. Typical application examples are multiple small coax cables. The energy output of a top quality hot-bar is quite high. A hot-bar as small as 10mm can generate as much as 4000 Watt in comparison with maximum 50 Watt to get a conventional solder iron and 30 Watt for diode laser soldering. This enables short process times and good solder results on parts having a high-energy requirement, like MCPCB and ceramics. HBR Soldering is really a process that is reproducible, quantifiable, and traceable to quality standards like ISO / NIST. It really is safe for that operator, highly operator independent and simple to automate.
The Recent-Bar or thermode is mounted to your bonding head through a quick connect block. The bonding head has a accurate and stable linear guidance for your hot-bar. Movement is performed having a pneumatic cylinder or perhaps an electrical motor. An inside spring system generated an accurate force. Most reflow joints of the nature require fewer than 100 Newton pressure. Force needs to be calibrated and set up on the correct level to have the right transfer of thermal energy towards the solder joint. The bonding head should have a precise coplanarity adjustment to set the flatness from the thermode for the product accurately. These heads are modular in construction and therefore versatile for integration.
After the start signal is provided, the Robotic Soldering Machine is gently lowered until it seats around the product. The top senses this. Force is build up till the preset force is reached. When the right force is reached, a signal is passed for the power source, which starts heating up the-bar.
At this point, the new-bar holds across the product with all the preset force. The new-bar is at “room temperature”. The solder control unit, also called “SCU” or “power supply” has brought the beginning signal to the soldering process.
The SCU sends current from the hot-bar. The new-bar is designed to ensure the electrical resistance is highest at the end (where it touches the product). Heat is generated due to the blend of current and electrical resistance. A small thermocouple is welded in the front of thermocouple. This thermocouple feeds back the specific hot-bar temperature for the SCU. This makes a total closed-loop regulation for the temperature-time cycle.
Normal rise time for most hot-bars is 1.5 to 2 seconds, equalling a heating rate of about 200 degrees Celsius a 2nd. The newest generation of solder control unit is managing the temperature all the way through the warming up phase. As soon as the “REFLOW temperature” is almost reached the solder control unit needs to 15dexopky along the heating rate to prevent a temperature overshoot. A great solder control unit and hot-bar combination will make up for all variations in heat-loads that can occur during normal production circumstances.
This design has both sides from the polyimide (kapton) material removed, leaving the traces free of insulation. The hot-bar contacts the traces directly and conducts heat towards the parts. If the PCB pads and hot-bar footprint are sized correctly, this design is going to be most tolerant to excess solder about the pads, as solder may flow into open areas. During the process, solder will also wet to the peak of your trace. Caution must be exercised in part handling as the traces might be easily bent or damaged. Because of the direct hot-bar to steer contact, this design may have low hot-bar temperatures and short process times. The-bar will pollute with flux residues, and may require cleaning. A kapton feeder module (start to see the section on equipment) will solve these objections.
This design has the polyimide removed in one side only. Heat is conducted through the hot-bar throughout the solid polyimide surface towards the exposed traces
underneath. The polyimide conducts heat through the insulation for the exposed traces and pads around the PCB. The polyimide thickness in the joint area is limited to around 50 microns, enabling conduction. When the LED Soldering Machine needs to be heated past 400 – 425°C, burning of polyimide and hot-bar contamination migh result. This design is less tolerant of excess solder in the PCB pads because little room exists for excess to flow. The one-sided flex is best suited for small pitches. Pitches no more than 200 micron, arranged in a few rows, are possible.