Island-free lead frame structure prefilled with plastic encapsulating material, plated firstly and etched later and production method thereof

Abstract

A method for manufacturing an islandless lead frame structure (100) for semiconductor packaging includes providing a metal substrate, forming a first photoresist film on the top surface of the metal substrate, and forming a top surface plating pattern in the first photoresist film using photolithography. The metal also includes performing a plating process on the top surface and the back surface of the metal substrate to form a first metal layer (5) on the top surface and a second metal layer (6) on the back surface. Further, the method includes performing an etching process on the top surface and the back surface of the metal substrate simultaneously using a top surface etching pattern and a back surface etching pattern as the respective masks to form etched regions in the metal substrate and a plurality of leads (2), without forming any island. Further, the method includes removing the third photoresist film and the fourth photoresist film, and pre-encapsulating the etched metal substrate using a molding compound (4) to form the pre-encapsulated lead frame structure.

Description

technical field [0001] The invention relates to a lead frame structure and a production method thereof, belonging to the technical field of semiconductor packaging. Background technique [0002] There are two main types of traditional lead frame structures: [0003] One is the four-sided flat no-lead package (QFN) lead frame. In order to prevent the lead frame from being sealed on the front side of the lead frame, the back of the lead frame will produce overflow of the plastic packaging compound, so the lead frame is attached to the back of the lead frame. with an expensive high temperature adhesive film (such as Figure 14 shown), this lead frame structure has the following disadvantages: [0004] 1. A layer of high temperature resistant adhesive film is attached to the bottom of the metal lead frame, which increases the cost of the lead frame by at least 50%; [0005] 2. The adhesive film attached to the bottom of the metal lead frame is a soft organic substance, so in t...

AI Technical Summary

Problems solved by technology

[0004] 1. A layer of high temperature resistant adhesive film is attached to the bottom of the metal lead frame, which increases the cost of the lead frame by at least 50%;

[0005] 2. The adhesive film attached to the bottom of the metal lead frame is a soft organic substance, so in the subsequent packaging process of chip loading and wire bonding operations, volatile pollution of organic substances will be generated due to high-temperature baking, which will directly pollute The bonding between the front of the chip and the front of the lead frame and the wire bonding will even affect the failure of the bonding ability with the plastic encapsulant during the subsequent packaging process between the front of the chip and the front of the lead frame (commonly known as delamination);

[0006] 3. Because the soft organic adhesive film is attached to the bottom of the lead frame, part of the bonding force is absorbed by the soft organic adhesive film during the subsequent wire bonding operation in the packaging process, increasing the wire Difficulty in bonding, resulting in instability of wire bonding yield, which may cause reliability problems;

[0007] 4. Because the soft organic adhesive film is attached to the bottom of the lead frame, the metal wire material is limited to soft and expensive gold wire during bonding, instead of hard and low-cost copper and aluminum. quality or other low-cost wire or strip;

[0009] 6. Usually, QFN products must have a metal base island before they can be mounted. Sometimes it will bring some troubles to the circuit board design, because it is necessary to prevent the short circuit between the line and the metal base island.

[0011] 1. The production process of the lead frame is too complicated, resulting in an increase in the cost of the lead frame;

[0012] 2. The etching of the lead frame is divided into upper and lower etching once, which is easy to cause misalignment due to repeated positioning errors of the upper and lower etching positions

Images