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December 13, 2019
Bottom Side Chip Bonding
When should we use adhesive to bond SMT components to the bottom side of a double sided PWA before going thru reflow soldering? Component size, weight, etc.
D.M.
December 12, 2019
Pre-bake in a Vacuum
Can the time for pre-baking of components and bare PCBs to eliminate moisture be reduced by using a vacuum oven? What percent of bake time reduction could we expect?
E.B.
December 11, 2019
Class 2 vs. Class 3
Where are the mayor differences in class 2 and class 3 other than in the IPC-A-610 standard? In which standards is the difference most significant and notable?
A.M
December 10, 2019
Automatic Insertion Causing Plated Hole Damage
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During the automatic insertion of 2 pin components, and after clinching the pins, we encounter a small deformation and/or sometimes small crack in the land or wall of the plated hole.
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We need to use a mechanical clinching method per the customer request. These 2 pin components must sit flat on the PCB, with no tilt. What can we do to reduce or eliminate the plated hole damage. What is the criteria for acceptability of cracks and deformation of the plated hole wall?
M.C.
December 9, 2019
Flux Oozing from Insulated Wires
We have a problem with flux and wiring. Our wires are stripped and tinned. It appears that throughout the build cycle flux oozes out from under the insulation. We clean and find later in the process that flux seeps out again.

What could cause this?
K.C.
December 6, 2019
Bromine Free PWBs
What are the pros and cons of bromine in PWBs?Several of our customers require bromine free PWBs, but some of our suppliers do not think that is a good way to go. Are bromine and lead free connected?
E.C.
December 5, 2019
Glued SMT Components Falling Off
We are having issues with glued SMD capacitors falling off after going through the oven curing process. We are using well known adhesive from a quality supplier.

The issue is erratic and we have no problem with SMD resistors. Why does this problem happen only with capacitors and not resistors. The components are very similar in size?
N.K.
December 4, 2019
Insufficient Plated Hole Fill with Electrolytic Capacitors
We are having problems achieving the minimum hole of 75% on electrolytic capacitors using our wave soldering. What do you suggest?
W.E.
December 3, 2019
Gold Edge Contact Flux Contamination Failures
We received somere turned circuit board assemblies that failed after some time in the field. These assemblies were originally processed using no-clean flux. The assemblies had visible contamination on the gold edge contacts and analysis confirmed that there was flux residue on the gold edge contacts.

We sent the assemblies back to the EMS supplier to properly clean them. The EMS supplier claims that the residue on the gold edge contacts alone would not cause functionality problems. What do you say?
L.C.
December 2, 2019
Twisting Multi-strand Wires
Should multi-strand wires be twisted before they are tinned with solder? What are the benefits of twisting prior to tinning?
A.S.
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