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 result in 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 standard soldering process for the reason that the reflow of solder is accomplished utilizing a heating element called a thermode which happens to be heated and cooled down for every connection. Pressure is used through the entire cycle including heating, reflow, and cooling. This technique is mostly employed to connect flexfoils to Printed Circuit Boards.
With Automatic soldering machine is applied through the entire cycle,including heating, reflow and cooling. Because pressure is appliedduring the total cycle, the procedure is very ideal for parts that will jump loose during cooling down when soldered with many other techniques. Typical application examples are flexfoils, small wires, very light or small components, etc. The position of the parts is extremely accurate because the pressure is used during cooling down. For components that require a really precise positioning after being soldered HBR Soldering is regarded as the ideal process.
And opposed to traditional soldering, pulse-heated soldering reflows solder simply by using a thermode which is heated and cooled off for each and every connection. This selective heating-up of simply a small area of the components helps to make the process very suited to soldering heat-sensitive parts. Typical application examples are CCD camera chips, connectors, etc.
With HBR Soldering all connections to become made simultaneously. Up to 200 leads or wires can be connected in one 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 top quality hot-bar is extremely high. A hot-bar as small as 10mm can generate as much as 4000 Watt when compared with maximum 50 Watt for the conventional solder iron and 30 Watt for diode laser soldering. This lets short process times and good solder results on parts with a high-energy requirement, like MCPCB and ceramics. HBR Soldering is a process that is reproducible, quantifiable, and traceable to quality standards like ISO / NIST. It really is safe to the operator, highly operator independent and simple to automate.
The Recent-Bar or thermode is mounted to your bonding head by means of a quick connect block. The bonding head has an accurate and stable linear guidance to the hot-bar. Movement is done using a pneumatic cylinder or even an electrical motor. An inside spring system generated an exact force. Most reflow joints of the nature require less than 100 Newton pressure. Force must be calibrated and set up to the correct level to obtain the right transfer of thermal energy to the solder joint. The bonding head should have a precise coplanarity adjustment setting the flatness in the thermode for the product accurately. These heads are modular in construction and so versatile for integration.
Right after the start signal is offered, the Robotic Soldering Machine is gently lowered until it seats on 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 supply, which starts warming up the hot-bar.
Presently, the new-bar holds across the product with all the preset force. The-bar reaches “room temperature”. The solder control unit, also called “SCU” or “power supply” has received the start signal for that soldering process.
The SCU sends current with the hot-bar. The hot-bar is made in order that the electrical resistance is highest towards the bottom (where it touches the product). Heat is generated because of the combination of current and electrical resistance. A small thermocouple is welded about the front of thermocouple. This thermocouple feeds back the particular hot-bar temperature to the SCU. This will make a total closed-loop regulation for that temperature-time cycle.
Normal rise time for almost all hot-bars is 1.5 to 2 seconds, equalling a heating rate of around 200 degrees Celsius an additional. The most up-to-date generation of solder control unit is managing the temperature right through the warming up phase. When the “REFLOW temperature” is almost reached the solder control unit has to 15dexopky along the heating rate to prevent a temperature overshoot. An excellent 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 either side in the polyimide (kapton) material removed, leaving the traces clear of insulation. The new-bar contacts the traces directly and conducts heat on the parts. If the PCB pads and hot-bar footprint are sized correctly, this design will probably be most tolerant to excess solder on the pads, as solder may flow into open areas. During the process, solder will even wet to the very top from the trace. Caution must be exercised in part handling as being the traces can be easily bent or damaged. Because of the direct hot-bar to lead contact, this design can have low hot-bar temperatures and short process times. The-bar will pollute with flux residues, and can 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 with the solid polyimide surface on the exposed traces
underneath. The polyimide conducts heat with the insulation on the exposed traces and pads on the PCB. The polyimide thickness within the joint area is restricted to around 50 microns, enabling conduction. In case the LED Soldering Machine must 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 are available for excess to flow. The single-sided flex is the most appropriate for small pitches. Pitches as small as 200 micron, arranged in a couple of rows, are possible.