Technical Articles and White Papers
Browse our library for some of the most popular published articles that you may find useful in your efforts to improve your process results.
Some of the recent "Short Scoop" articles are part of an exciting column series by our Rachel Miller-Short with SMT Magazine.
Screen Printing Solutions for Small Die &
Precision Alignment Challenges - PDF AVAILABLE
When you have a gold Kovar tab, and you need to exactly and precisely place a solder fillet on this tab, and the tab is only 0.063 +/- 0.002 x 0.125 +/- 0.002 inches, how do you do it? There can be no gas pockets and no voids on the fillet anywhere. Reflow is expected to be perfect. And to make the situation more challenging, the customer is trying to get away from hand soldering and wants to use machine placement. This was the task Plexus Manufacturing Solutions, Boise, Idaho asked Photo Stencil engineers to solve. A uniquely designed aperture shape helped solve the problem.
Printing and Assembly Challenges for Quad Flat No-Lead Packages - PDF AVAILABLE
With proper stencil design, stencil technology selection, and PCB solder mask layout the challenges that QFNs present to the assembly process can be overcome.
Electroformed vs. Laser-cut: A Stencil Performance Study - Download PDF
This study confirms that the electroformed stencil provides better print performance than an electroformed nickel foil stencil with laser-cut apertures. The difference is more pronounced with lead-free than tin/lead solder paste. Mirror aperture walls provided by growing nickel, atom-by-atom, around photoresist pillars in the electroform stencil process release solder paste better than laser-cut electroformed foil stencil walls.
The Small Component Printing Challenge - Download PDF
Discusses very small components and why are they troublesome: .3 mm pitch CSP devices, .3 mm pitch QFN devices, 01005 passive devices. Positional accuracy is a challenge for PCB, the stencil, the pick and place, as well as the stencil printing equipment. The devices above typically have pad sizes on the PCB in the 125-micron (5 mil) to 200-micron (8 mil) range.
The BGA/QFN Repair Process - Download PDF
Repairing a PCB with a defective BGA, micro-BGA, or QFN often is a challenging and tedious
task. The conventional method is to remove the defective device, clean the pads on the PCB,
then print solder paste on the pads with a mini-stencil. The stencil footprint must be small
enough to fit into the area of the removed part, which typically is surrounded by other devices in close proximity. An alternative repair method is to print solder paste directly onto the QFN pads or the BGA solder balls using a specialized tool.
Duplicate Exact from the Stencil Perspective
Technology Drives New Stencil Applications
Rework Challenges, Rework Solutions
Creative Solutions to Stencil Printing Challenges
Critical Parameters for Stencil Performance
Intrusive Reflow of Lead-free Solder Paste
Intrusive Reflow of Lead-free Solder Paste, Part II
The Evolution of Stencil Technology
Intrusive Reflow Challenges Wave Soldering
Choosing a Stencil
Step 4: Printing
Stencil Design for Mixed-technology Placement & Reflow