Pulsed-Heated Hot-Bar Reflow Soldering can be a selective soldering process where two pre-fluxed, solder coated parts are heated to a temperature sufficient to cause the solder to melt, flow, and solidify, forming a lasting electro-mechanical bond in between the parts and solder. Pulse heated soldering differs from the conventional soldering process in this the reflow of solder is accomplished employing a heating element called a thermode that is heated and cooled down for every connection. Pressure is applied through the entire cycle including heating, reflow, and cooling. This procedure is most commonly used 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 entire cycle, the process is very appropriate for parts that might 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 position of the parts is incredibly accurate since the pressure is applied during cooling down. For components that need an incredibly precise positioning after being soldered HBR Soldering is the most ideal process.
And against traditional soldering, pulse-heated soldering reflows solder simply by using a thermode that is certainly heated and cooled down for every connection. This selective heating-up of only a small portion of the components makes the process very ideal for soldering heat-sensitive parts. Typical application examples are CCD camera chips, connectors, etc.
With HBR Soldering all connections to be made simultaneously. Up to 200 leads or wires might be connected in a single process cycle (typically around just a few 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 ability production of a quality hot-bar is quite high. A hot-bar no more than 10mm can generate approximately 4000 Watt in comparison with maximum 50 Watt for any conventional solder iron and 30 Watt for diode laser soldering. This allows short process times and good solder results on parts having a high-energy requirement, like MCPCB and ceramics. HBR Soldering is actually a process that is reproducible, quantifiable, and traceable to quality standards like ISO / NIST. It is actually safe to the operator, highly operator independent as well as simple to automate.
The New-Bar or thermode is mounted to a bonding head by means of a quick connect block. The bonding head has a accurate and stable linear guidance to the hot-bar. Movement is performed having a pneumatic cylinder or an electrical motor. An inside spring system generated an exact force. Most reflow joints with this nature require fewer than 100 Newton pressure. Force needs to be calibrated and set towards the correct level to obtain the right transfer of thermal energy on the solder joint. The bonding head should have an exact coplanarity adjustment to create the flatness in the thermode to the product accurately. These heads are modular in construction and for that reason versatile for integration.
After the start signal is offered, the Auto Soldering Machine is gently lowered until it seats in the product. The pinnacle senses this. Force is increase up until the preset force is reached. If the right force is reached, a signal is passed to the power source, which starts warming up the recent-bar.
Right now, the recent-bar holds along the product with all the preset force. The recent-bar is in “room temperature”. The solder control unit, also called “SCU” or “power supply” has brought the beginning signal for that soldering process.
The SCU sends current with the hot-bar. The hot-bar was created in order that the electrical resistance is highest at the end (where it touches the merchandise). Heat is generated because of the mix of current and electrical resistance. A small thermocouple is welded around the front of thermocouple. This thermocouple feeds back the specific hot-bar temperature on the SCU. This may cause a complete closed-loop regulation for the temperature-time cycle.
Normal rise time for many hot-bars is 1.5 to 2 seconds, equalling a heating rate of around 200 degrees Celsius another. The newest generation of solder control unit is managing the temperature all the way through the warming up phase. Once the “REFLOW temperature” is nearly reached the solder control unit must 15dexopky down the heating rate to avoid a temperature overshoot. An excellent solder control unit and hot-bar combination will compensate for all variations in heat-loads that can occur during normal production circumstances.
This design has each side of your polyimide (kapton) material removed, leaving the traces without any insulation. The hot-bar contacts the traces directly and conducts heat for the parts. If the PCB pads and hot-bar footprint are sized correctly, this design is going to be most tolerant to excess solder in the pads, as solder may flow into open areas. During the process, solder will even wet to the top level of the trace. Caution has to be exercised in part handling because the traces may be easily bent or damaged. Due to direct hot-bar to steer contact, this design will have low hot-bar temperatures and short process times. The hot-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 got the polyimide removed on one side only. Heat is conducted through the hot-bar from the solid polyimide surface on the exposed traces
underneath. The polyimide conducts heat throughout the insulation towards the exposed traces and pads on the PCB. The polyimide thickness within the joint area is limited to around 50 microns, enabling conduction. When the LED Soldering Machine should be heated past 400 – 425°C, burning of polyimide and hot-bar contamination migh result. This design is less tolerant of excess solder about the PCB pads because little room are available for excess to flow. The only-sided flex is best suited for small pitches. Pitches as small as 200 micron, arranged in a few rows, are possible.