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 involving the parts and solder. Pulse heated soldering is different from the regular soldering process in that the reflow of solder is accomplished employing a heating element referred to as a thermode that is heated and cooled down for every connection. Pressure is used during the entire cycle including heating, reflow, and cooling. This procedure is most often utilized to connect flexfoils to Printed Circuit Boards.
With Automatic soldering machine is used in the entire cycle,including heating, reflow and cooling. Because pressure is appliedduring the total cycle, the procedure is very appropriate for parts that could jump loose during cooling down when soldered with 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 applied during cooling down. For components which require an incredibly 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 is certainly heated and cooled off for each and every connection. This selective heating-up of only a small section of the components helps 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. Approximately 200 leads or wires may 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 high quality hot-bar is incredibly high. A hot-bar as small as 10mm can generate up to 4000 Watt in comparison to maximum 50 Watt for a conventional solder iron and 30 Watt for diode laser soldering. This lets short process times and good solder results on parts by using a high-energy requirement, like MCPCB and ceramics. HBR Soldering is a procedure that is reproducible, quantifiable, and traceable to quality standards like ISO / NIST. It can be safe for the operator, highly operator independent and straightforward to automate.
The Recent-Bar or thermode is mounted to some bonding head through a quick connect block. The bonding head has a accurate and stable linear guidance to the hot-bar. Movement is carried out using a pneumatic cylinder or perhaps an electrical motor. An inside spring system generated an accurate force. Most reflow joints with this nature require less than 100 Newton pressure. Force must be calibrated and set towards the correct level to obtain the right transfer of thermal energy towards the solder joint. The bonding head ought to have an accurate coplanarity adjustment to create the flatness from the thermode towards the product accurately. These heads are modular in construction and so versatile for integration.
Following the start signal is given, the Auto Soldering Machine is gently lowered until it seats about the product. The pinnacle senses this. Force is build-up till the preset force is reached. As soon as the right force is reached, a transmission is passed for the power supply, which starts heating up the-bar.
Presently, the recent-bar holds down the product using the preset force. The-bar is at “room temperature”. The solder control unit, otherwise known as “SCU” or “power supply” has gotten the beginning signal to the soldering process.
The SCU sends current from the hot-bar. The new-bar is designed in order that the electrical resistance is highest in the bottom (where it touches the merchandise). Heat is generated due to mix of current and electrical resistance. A little thermocouple is welded on the front of thermocouple. This thermocouple feeds back the actual hot-bar temperature to the SCU. As a result a total closed-loop regulation to the temperature-time cycle.
Normal rise time for many hot-bars is 1.5 to 2 seconds, equalling a heating rate of about 200 degrees Celsius another. The latest 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 should 15dexopky on the heating rate to prevent a temperature overshoot. An excellent solder control unit and hot-bar combination will compensate for all differences in heat-loads that may occur during normal production circumstances.
This design has either side in the polyimide (kapton) material removed, leaving the traces without any insulation. The-bar contacts the traces directly and conducts heat towards the parts. When the PCB pads and hot-bar footprint are sized correctly, this design will be most tolerant to excess solder on the pads, as solder may flow into open areas. Along the way, solder will also wet to the peak of your trace. Caution needs to be exercised in part handling as being the traces could be easily bent or damaged. Due to the direct hot-bar to lead contact, this design will have low hot-bar temperatures and short process times. The new-bar will pollute with flux residues, and will require cleaning. A kapton feeder module (begin to see the section on equipment) will solve these objections.
This design offers the polyimide removed on one side only. Heat is carried out through the hot-bar through the solid polyimide surface to the exposed traces
underneath. The polyimide conducts heat from the insulation to the exposed traces and pads in the PCB. The polyimide thickness within the joint area has limitations to about 50 microns, enabling conduction. In the event the LED HotBar Machine has to be heated past 400 – 425°C, burning of polyimide and hot-bar contamination might 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 as small as 200 micron, arranged in a few rows, are possible.