Reflow – Explained With Procedure.
Reflow soldering is the most common process used by manufacturers and repair shop to mount electronic components on a printed board circuits and reflow is the stage of “reflowing solder” where the solder or solder paste changes its state from solid to liquid at the high heat temperature to make solder joint on PCB (printed board circuits).
Types Of Reflow Method
There are four types of reflow method:
Hot Air Pencil – It’s a pencil like hot air blower which is normally attached to a box who supplies the air pressure through connection pipe to the pre-heated pencil to make a hot air pressure and that hot air can be used to do some soldering work.
This pencil is the best and affordable option when we’re doing soldering on some SMD Electronic Components.
Wave Solder Reflow – Wave soldering is a process of filling holes on printed circuit board by liquid solder to joint electronic components who pre-attached into those holes on PCB for making a solder joint and electrical connection.
Wave solder is done by wave solder machine who take your motherboard or PCB from the one side of the machine and parcel to the other end by floating your PCB on the liquid solder and that melted solder soaked by the holes in your PCB and remains stick to it.
Wave reflow is the alternative way of making solder joint by soldering iron and also the quicker than that.
Convection Reflow – It’s a process of melting solder who applied on components by heating in a convection oven to make a solder joint.
This is a great way to mount bulk amount of electronic components of a PCB.
Vapor Phase Reflow (VPR) – It’s a new technology used at some point for making solder joint by boiling PCB in the liquid.
#Something About The Reflow Process
There are four stages of reflow and all are important in order to fix something without breaking them. These all stages can make a proper solder joint by providing accurate heat on an accurate time period for maintaining the changes in temperature because providing a high temperature directly to a PCB can broke its electronic components.
All reflow profiles consist of four distinct stages.
- Thermal Soak
- Cool down
At this preheating stage, you’re going to provide decent heat on the printed circuit board to bring up the temperature. Normally we use this preheating stage whenever we’re baking our PCB in a convection oven or doing Vapor Phase Reflow.
This stage can take up to 60 seconds at the speed of 2 degrees C per second of rising heat when doing an oven reflow and VPR rates may higher that because a vapor can absorb more heat that a normal air.
During this state, the component on the PCB gets warmer and solder flux starts to melts and makes your circuit board to gets ready for baking.
“Preheat Stage – 100 °C in 60 sec”
THERMAL SOAK STAGE
We start the thermal soak stage after when the 60 sec of preheating stage gets completes and at this stage we are going to rise heat up to 180 degrees C and that makes the solder paste/balls near to the melting point.
During this stage, we provide heat at the rate 1 degree C per 2 sec until it gets to 180 degrees and starts to passing off solder readily in the form of vapor. This stage also activates the solder flux which prevents oxidation of the base and filler materials.
120 second is the maximum recommendation for the thermal soaking process and the heat should not get more that 180 degree Celsius and if the heat stays low, it can be possible the flux may not fully activate.
“Thermal Soak Stage -150 °C to 165 °C in 120 sec”
At this stage, the temperature goes to higher that the melting point and change the solder to liquid from its solid state. It will allow melted solder to fill the joint gaps and make a proper connection to conduct electricity and signals frequency.
During this stage, the rate of temperature increases rapidly to a specified level like above 235 degrees C for about 20 sec and the flux action occurs and good wetting is obtained.
Maintaining the temperature is a must in this stage, if its gets low, it can remain the solder joint dull or grainy looking or if it gets high it can damage or broke the IC’s on the Circuit board.
“Reflow Stage -235 °C to 265 °C in 20 sec”
COOL DOWN STAGE
This is final and the last stage of this reflowing process and it refers to a process of cooling down the temperature of PCB right after doing the reflow job.
During this stage, we turn off the heat and waiting for the temperature to get decrease for making the liquid solder joint hard rock. The size of solder grain can also depend on the drop rate of temperature and normally it will cool down as quickly as possible.
#Reflow On GPU
Doing reflow on a laptop’s or graphic card GPU is an old technique to fix no display screen output and sometimes it becomes the cheapest way to fixing stuff by just using a home oven.
“I’ve recently suggested this method to mike who questioned me about a black blank screen on his laptop and he tried everything what I said according to my other tutorial about reflowing a laptop, listed below. When he has done with the process of reflow and after that, he switches on the laptop, you know what happened, he got a repaired laptop on its side and the best part is he won’t spend any single penny.”
You can use reflow to fix your laptop if you don’t have that amount of money for reballing GPU chip:
Stuff You Can Use Besides Doing an Expensive Convection Reflow Oven Baking
- Hot Air Pencil
- Hair Dryer
- SMD Hot Air Blower Machine
- Toaster Oven (Not Microwave)
::: Suggestion links :::
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