How to solder EPC2034 GaN transistor?

We want to solder an EPC2034 GaN transistor to a costume-made PCB. We watch this video on youtube (EPC eGaN FET Die Attachment Tutorial - YouTube) and also read this document (, but still, we are not sure how can we solder an EPC2034 transistor to a PCB. In the video, it is mentioned a flux should be applied to the pads. What is this flux for? and where can I buy it? Also, where should I apply the solder? on the PCB (i.e., pads) or on the transistor (i.e., dies)?

Thanks for any help.


I wanted to let you know that I have forwarded your questions to our Product Manager for his advice and I will get back to you as soon as I have that information.

Hello, here are some tips from my Product Specialist:
Here is a tacky flux that Digikey carries as mentioned in the video:

You will need to make sure they get one that works for you.

Here is a good description regarding flux: What Is Solder Flux And How Do You Use It?

The placement of the solder is best on the solder pads as it would be easier to manage.

Hi again - I received another reply on your questions: be advised that the part already has some solder on it; hence “bumped die” it is much like a “BGA” package that has solder balls already on the contacts, only difference really is the bumped die package has elongated solder bumps.

Hello Jenny,

Thanks for your information. Regarding your last email, do you mean that the ball die under EPC2034 transistor has solder and we do not need to apply any solder on the PCB? Actually, since I am a mechanical engineer it is not still clear for me.

Thanks for your help,

That would be a correct statement.

Typically with solder bump and ball grid parts, the amount of solder already adhered to the part is plenty, though I have heard a few folks who wet the pads a bit with extremely small solder tinning as it were; really depends on how well your heating process works and your flux;

Assuming this is for a business use, I recommend you use a contract manufacturer to solder this device so that you don’t have a failure in a few months or years. Depending on your location you may even be pleasantly surprised to find a number of small PCB assembly houses within a couple hundred miles of you.

Reliably soldering BGA’s is a specialized field that in a professional setting uses specialty equipment costing many thousands of dollars. I’ve been soldering professionally for over 40 years as Chief Engineer at a small electronics manufacturer and over 50 years total. However, I would still not attempt soldering that BGA if it’s destined for a customer or needs to operate reliably for years in the factory. If it was for a prototype I’d give it a try myself after reading a number of hobbyist articles about soldering similar BGA assemblies.