Top mistakes engineers make who think they know how to solder

Top 7 Mistakes Engineers Make in Performing PCB

Rework

Bob Wettermann, MIT December 2015

Your BEST choice in PCB Test/ Rework/Repair and Solder Training & Tools www.solder.net

BGA Rework-Big Challenges

I. Drivers for Soldering Challenges-Pitch, Thin Packages, Small Packages, Higher Density, Higher Temps

II. Top “7” Soldering Errors Engineers Make

Incorrectly-Sized Soldering Tips

Use bottom side heaters

You can do this-BGAs

You can do this QFNs

Proper wicking-don’t pull up pads!

Liquid flux-better wetting, cleaning the soldering area

Get in get out, don’t hang out!




#1 Tip size selection

As large as possible

without overhanging pad area

no damage to PCB

Apply to maximum mass point of solder joint

Rapid thermal elevation


#2 -Use bottom side heaters for lead free rework


StencilQuik™-How Does It Work?

Step 1-Prepare site

Step 3-Squeegee

paste or flux though aperatures

Step 4.Place device & Reflow

Step 2-Place StencilQuik™ into

position

#3 You can do this-Place a BGA


StencilQuik™-Prototype Shop Value

Proposition

•StencilQuick™ allows developers and technicians to reliably hand place

BGAs when prototyping

•StencilQuick™ acts as a mask for damaged solder mask areas

underneath a BGA eliminating the need to repair damaged mask found

many times on “fast turn around” PCBs



Part Bumping Using a Polyimide Peel-n-Stick Stencil(s)

“Bump” part with one stencil, place “bumped” part into second stencil on board

#4 You can do this-Place a QFN


Step #1

Align and apply stencil to

device. Roll solder paste

through apertures.



Step #2

Reflow per solder mfr’s profile

recommendations



Step #3

Remove stencil and

clean. Surface now is “bumped”



Inspection of “bumped” device



Step #4

Prep land area on PCB where device

is to be placed



Step #5

Align and adhere board

stencil on PCB. Roll

solder paste into apertures and clean off

residue.



Step #6

Place “bumped” QFN into stencil

apertures. Feel the

“bumps” fit into the

apertures



Step #7

Reflow as per solder paste

manufacturers’ profile

recommendations. Perform visual

inspection. Perform X-ray

inspection.



Wicking • Soldering station • Proper soldering iron tip • Soldering wick • Cleaning media • Soft brush • Flux paste

#5 Proper Wicking Procedure


Damaged/Lifted Pads Post Removal






#6 Apply (and clean off) Flux


#7 Get In, Get Out, Don’t Hang Out!


Lurking Challenges

0.3mm pitch

Lower temp solders

01005 components

Bob Wettermann, MIT [email protected]

More Questions?

Engineering

Top mistakes engineers make who think they know how to solder