T.J. Hughes

T.J. Hughes has submitted responses to the following questions.

Reflow Profile for Mixed Lead-Free and Leaded
The solder paste used is the primary determining factor for the profile you develop. ...

IPC-A-610 Class 3 - IPC-A-600 Class 2
Yes, they are two different standards, the IPC-A-610 does reference the 600 in many spots, but here is reference I ...

Selective Solder System Purchased At Auction
The best way is to replace the solder pot altogether, along with all the nozzles/tips that will have been "contaminated" ...

Requirement for Toe Fillets
It's hard to tell, but it seems as if you may be using an older revision of the IPC-A-610. To ...

Mixed Process Solder Joint Appearance, Smooth or Grainy?
I would expect them to be smooth and shiny, assuming your profile is correct. We currently build both RoHS and ...

QFN Open Solder Joints
I would validate the amount of paste being deposited in the center/thermal area.If there it is 1:1 aperture to pad, ...

Stencil Cleaning Frequency
I'm not aware of an "industry standard" as far as time between cleanings goes,usually it's set up based on frequency ...

Customer Approval for Repairs
It may depend on the type of defect and the repair performed, whether or not the assemblies performance could be ...

Solder Paste Prep Before Use
I'drecommend more time out of the refrigerator, say closer to 4 hours minimum tomake sure the entire jar gets to ...

Hand Soldering at Low Temperature
As long as you get the temperature up to the melting point and keep it there while the solder/flux does ...

Manual or Automated Assembly?
Tough question without knowing what soldering equipment, supplies, or the state of your components/PCB's you are using, as well as ...

Exposed Copper Risk
The copper will be more susceptible to oxidization, but will likely not cause too much more of a risk for ...

Components Jumping Around During Reflow
The wetting action with Lead Free processes and components is typically slower than a leaded process, which doesn't allow the ...

How Many Fiducials Per Solder Paste Stencil?
Since fiducials are used for alignment, the amount can vary from 2-3 to as many as the customer wants. A ...

How To Rework SMT Connector with Center Ground Strip
I'd recommend that you use a hot-air wand to remove, assuming you don't have to salvage the connector, making sure ...

Adhesion Problems with Conformal Coating
Goingto a Silicone based conformal coating could help with the cracking. As far as adhesion goes, making sure the surface ...