Pulsed-Heated Hot-Bar Reflow Soldering can be a selective soldering process where two pre-fluxed, solder coated parts are heated into a temperature sufficient to result in the solder to melt, flow, and solidify, forming a permanent electro-mechanical bond between the parts and solder. Pulse heated soldering is different from the regular soldering process because the reflow of solder is accomplished utilizing a heating element termed as a thermode that is heated and cooled off for every single connection. Pressure is used throughout the entire cycle including heating, reflow, and cooling. This method is most frequently employed to connect flexfoils to Printed Circuit Boards.
With hot bar soldering machine is used throughout 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 as the pressure is used during cooling down. For components which require a really precise positioning after being soldered HBR Soldering is regarded as the ideal process.
And against traditional soldering, pulse-heated soldering reflows solder through a thermode that may be heated and cooled off for every single connection. This selective heating-up of merely a small part of the components makes the process very appropriate for 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 may 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 strength production of a quality hot-bar is quite high. A hot-bar as small as 10mm can generate approximately 4000 Watt in comparison to 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 can be a procedure that is reproducible, quantifiable, and traceable to quality standards like ISO / NIST. It can be safe for that operator, highly operator independent and easy to automate.
The-Bar or thermode is mounted to a bonding head through a quick connect block. The bonding head comes with an accurate and stable linear guidance for the hot-bar. Movement is done with a pneumatic cylinder or an electrical motor. An internal spring system generated a precise force. Most reflow joints with this nature require less than 100 Newton pressure. Force ought to be calibrated and set to the correct level to obtain the right transfer of thermal energy towards the solder joint. The bonding head ought to have a precise coplanarity adjustment to put the flatness of the thermode to the product accurately. These heads are modular in construction and for that reason versatile for integration.
Once the start signal is given, the Robotic Soldering Machine is gently lowered until it seats about the product. Your head senses this. Force is increase till the preset force is reached. If the right force is reached, a transmission is passed on the power source, which starts warming up the hot-bar.
By now, the new-bar holds along the product with the preset force. The recent-bar are at “room temperature”. The solder control unit, otherwise known as “SCU” or “power supply” has gotten the beginning signal for the soldering process.
The SCU sends current from the hot-bar. The new-bar was created in order that the electrical resistance is highest at the bottom (where it touches the item). Heat is generated due to mixture of current and electrical resistance. A tiny thermocouple is welded about the front of thermocouple. This thermocouple feeds back the particular hot-bar temperature towards the SCU. As a result an entire closed-loop regulation for the temperature-time cycle.
Normal rise time for the majority of hot-bars is 1.5 to 2 seconds, equalling a heating rate of about 200 degrees Celsius a second. The newest generation of solder control unit is governing the temperature all the way through the heating up phase. Once the “REFLOW temperature” is almost reached the solder control unit must 15dexopky along the heating rate to avoid a temperature overshoot. A good solder control unit and hot-bar combination will make amends for all differences in heat-loads that will 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 on the parts. In case 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. Along the way, solder will even wet to the top level of the trace. Caution should be exercised in part handling as the traces could be easily bent or damaged. Due to the direct hot-bar to lead contact, this design can have low hot-bar temperatures and short process times. The hot-bar will pollute with flux residues, and definately will require cleaning. A kapton feeder module (see the section on equipment) will solve these objections.
This design provides the polyimide removed on one side only. Heat is carried out in the hot-bar from the solid polyimide surface for the exposed traces
underneath. The polyimide conducts heat throughout the insulation on the exposed traces and pads about the PCB. The polyimide thickness within the joint area has limitations to around 50 microns, enabling conduction. When the LED HotBar Machine must be heated past 400 – 425°C, burning of polyimide and hot-bar contamination might result. This design is less tolerant of excess solder around the PCB pads because little room are available for excess to flow. The one-sided flex is best suited for small pitches. Pitches as small as 200 micron, arranged in a couple of rows, are possible.