Surface Mount Semiconductor Lead Plating via Dambar
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Solution Overview
Problem
Inconsistent solder pad formation and lead geometry in surface mount semiconductor devices can lead to weak or improperly formed solder joints, resulting in reduced functionality and potential failure of electronic circuits due to un-plated lead ends after singulation.
Innovation Solution
A method of manufacturing surface mount semiconductor devices involves mounting a semiconductor die on a support surface, attaching a leadframe with a dambar connecting a second lead region to a support surface, electro-plating the second lead region to ensure plated lead ends, and severing the dambar to expose the lead end for plating, ensuring electrical continuity and proper solder joint formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the leadframe is plated before singulation, then the leads are electrically connected to the outer frame for electroplating, but the lead ends become un-plated after cutting
Solution Approach 1:
The patent applies preliminary action by maintaining electrical continuity through the dambar connection during plating, ensuring that the lead ends are plated before they are severed from the support structure. This preliminary plating action prevents un-plated lead ends that would otherwise occur with conventional post-cut plating methods.
Solution Approach 2:
The dambar serves as an intermediary element that maintains electrical continuity between the outer frame and the lead ends during the plating process. This intermediary connection allows electroplating current to reach the lead ends that would otherwise be electrically isolated after cutting, ensuring complete plating coverage.
2Manufacturing precision
If the leads are severed from the outer frame before plating, then the lead ends are exposed, but electrical continuity for plating is lost
Solution Approach 1:
The patent performs plating as a preliminary action before severing the leads from the outer frame. This sequence ensures that electrical continuity is maintained during plating, allowing complete coverage of the lead ends including the distal ends that would otherwise be inaccessible or un-plated if cut first.
Solution Approach 2:
The patent inverts the conventional sequence by plating before cutting, rather than cutting before plating. This reversal of the standard process sequence solves the problem of un-plated lead ends by ensuring that the plating operation occurs while electrical continuity is still intact through the dambar connection.
3Manufacturing precision
If the dambar is removed before plating, then the leads are free to be plated, but the support structure is compromised
Solution Approach 1:
The patent performs plating as a preliminary action while the dambar is still in place providing structural support. The dambar is removed only after plating is complete, at which point its structural function is no longer needed. This sequence maintains both structural integrity and plating uniformity.
Solution Approach 2:
The dambar provides beforehand cushioning or support during the plating process, maintaining the structural integrity of the assembly while enabling uniform plating of the leads. After plating is complete, the dambar is removed as it has fulfilled its temporary support and electrical connection function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures that all lead ends are plated, enhancing the formation of strong solder joints and improving the reliability and functionality of surface mount semiconductor devices by maintaining electrical continuity during the electroplating process.
Implementation Method 1
the leadframe will typically be plated, by an electroplating process, with a metallic material
Implementation Method 2
electro-plating the second lead region with a metallic material
Implementation Method 3
a technique known as reflow is used to melt the solder paste and the leads of the SMD are electrically and mechanically bonded to the solder pads on the PCB
Implementation Method 4
Surface tension of the molten solder helps to align the leads of the SMD on their respective pads
Data Source
AI summary
A surface mount semiconductor device and method of manufacture. A semiconductor die is mounted on a first support surface; a leadframe is attached to the semiconductor die, the leadframe comprising: an electrical lead having a first lead region connected to the semiconductor die; and a second lead region distal the first lead region, wherein the second lead region is connected to a second support surface; encapsulating the semiconductor die, first support surface and the first lead region; the second lead region is severed from the second support surface to expose a lead end; and the second lead region is electro-plated with a metallic material, such that the lead end is coated with said metallic material.