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Hair dryer for logic board reflow?

Okay, so I had some time while I was waiting for parts to complete a few more projects. I did my daily browsing through "Answers" and thought it is time to clear up the debate about using a hair dryer for reflow purposes. There are plenty of question and answers about using a hairdryer to reflow either a X-Box or an iPhoneor any other device. To determine what temperatures are produced by either instrument, I assembled a few tools of my own. For this test I used my Dual Temperature 1500Watt heat gun, my families Goodies 1875Watt 2 speed hair dryer, my Lutron TM902C thermometer (range -50deg C to 750deg C), and a few left over ceramic tiles as insulators.

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I went ahead and sandwiched the end of the Type K thermocoupler between the ceramic tiles. This way I tried to eliminate variances caused by ambient temperatures as much as possible. It also protects the probe end from to much heat exposure.

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Ambient temperature in my shop during this test was 23deg C (73.4deg F). Pretty mild day for South Texas:-)

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First heat source I tested is the Goodys 1875watt 3speed hair dryer. It is set to Hot on high speed.

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At a distance between the heat source and the thermocoupler of 3/4" (19mm) the maximum temperature it reached was 63deg C (+/- 2deg C by moving the hair dryer in a back-and-forth motion across the thermal probe) (145.4deg F)

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Next up is the Dual Temperature 1500Watt heat gun. I used the same setup with the same distance between the heat source and the probe. With a distance of 3/4" (19mm) and the heat gun set to the first speed settings, the maximum temperature reached was 100deg C.(212deg F)

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With the heat gun speed at stage 2 the maximum temperature measured was 240deg C.(464deg F) The picture is somewhat deceiving since the angle of the heat gun is increased, so it appears as if it was directly over the thermocoupler. Proper distances have been maintained.

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To determine if a hair dryer was sufficient to reflow a board, I picked the solder available in my shop. It is the Sn-Ag-Cu (Tin-Silver-Copper) solder, that is also used by two thirds of Japanese manufacturers for reflow, and has a melting range of 217–220deg C or 422-428deg F . Lead containing solder, like the 63/37 Sn/Pb used principally in electrical/electronic work, has the lowest melting point of all the tin/lead alloys at 183deg C or 361.4deg F. I do recognize that the solidus quantifies the temperature at which melting of a substance begins, but not necessarily the substance is melted completely, is lower than the melting point, but this temperature is usually just a few degrees lower than the melting point

References are here and here

Hopefully this will make a definite case against using a hair dryer for any reflow attempt. It will not reach the temperature required to reflow any logic board. Of course this is just informational for those that wondered about this in the first place. Thanks for a great forum.

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Fantastic analysis!

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This could perhaps be turned into a rather informative guide catagorised as a "technique" explaining the best way to reflow a board etc.

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A hairdryer on high heat worked great for a 6th generation iPod nano and a 4th generation iPod touch.

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Awesome! Comparison is very nice. Sep by step information with pictures made so clear of the purpose. Thanks a lot for all the explanation and splendid effort.

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I actually had luck using a hairdryer. I did not have access to a heat gun at the time and on a whim used my hairdryer. It worked perfectly for me. Ive had this hairdryer for roughly 12 yrs. Idk if it makes a difference but I will point out that I was given this hairdryer from a friend who got it while she was in cosmetology school. It has 6 heating/airflow options. I have no idea how it compares to regular store bought hairdryers.

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Impressive!

The issue with hair dryer is the consistency in the heat directly from the hairdryer. It's not always consist (enough for electronics) and unless you stabilize the distance it's not recommended.

Also, the back of a hair dryer sucks in air to blow through the heat coils like a jet engine. All sorts of dust and elements in the air are slung on the electronic devices. Not such a big issue as it can be done.

Most people who re flow buy a hot plate. The temperate is accurate, air can blow over the top of your other components and you don't expose heat to other unnecessary areas.

We buy back broken LCD assemblies here in the USA from repair shops so this is a task that we do in overseas factory. We use the T-962 hot plate. You can get one for around $250 but there are other versions from $100 or so.

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So to sum it up, Heat gun good, Hair dryer bad. Does a hair dryer work as a substitute in other uses, such as loosening adhesive?

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Jack Ryan, in essence for a reflow, yes you are right. Heatgun goes, hair dryer no go:-). A hairdryer might be good to relieve the bond from some adhesives, especially some of the lesser brands. For most of the adhesives, I like to take a look at he MSDS sheets to determine their melting point. True, most adhesives will release their bonds way before that point is reached, but it does give an idea of their heat tolerance. For example the much cited "Gorilla Glue" is stated to " works well up to temperatures as high as 200-220ºF" so a hair dryer will not provide enough heat. Of course, the favorite would be the 3M product 200mp, which is a double sided tape used for electronic devices like iPod LCD's etc. According to the MSDS datasheet it does show a Temperature Resistance

Long Term (days, weeks): 250°F (121°C)

Short Term (minutes, hours): 300°F (149°C)

again, looks like trouble for the hair dryer. I'd give the heat gun, even at low settings, the preference. Hope this makes sense.

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Actually I would make an argument against using a general purpose heat gun to reflow a motherboard. It's easy to exceed maximum temperature of component and fry everything using a high powered heatgun, where as it's much safer to use a hair dryer, which cannot generate too high a temperature. Of course, electronic quality heat guns are different story, as these allow temperature to be controlled precisely. But this is just a warning from my experience of frying multiple motherboards using a general purpose heatgun, despite constantly monitoring the board temperature with IR thermometer. I even physically melted a bga chip down, even though my IR thermometer never indicated temperature above 160 degrees C!! So extra precaution is in order when attempting to use a general purpose heat gun for reflowing motherboards without fine control over temperature output.

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coldspring this was strictly done to see if a hairdryer can be used for a reflow. As the temperatures have shown it cannot. The hairdryer will not reach temperatures high enough to even get close to the melting point of any solder. I do agree that any reflow with any heat gun is a shotgun approach. A reflow should be done with the right tools only.

The reason why many believe that the hairdryer worked as a reflow tool was due to the repairs done on Xbox 360's and PS3's. All the hairdryer did on those, was temporarily close the gap of the solder bumb's of the flip chip designed processors. That process should have never been called a reflow.

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